ϟ

A. J. Bevan

Here are all the papers by A. J. Bevan that you can download and read on OA.mg.
A. J. Bevan’s last known institution is . Download A. J. Bevan PDFs here.

Claim this Profile →
DOI: 10.1140/epjc/s10052-008-0716-1
2008
Cited 146 times
B, D and K decays
The present report documents the results of Working Group 2: B, D and K decays, of the workshop on Flavor in the Era of the LHC, held at CERN from November 2005 through March 2007. With the advent of the LHC, we will be able to probe New Physics (NP) up to energy scales almost one order of magnitude larger than it has been possible with present accelerator facilities. While direct detection of new particles will be the main avenue to establish the presence of NP at the LHC, indirect searches will provide precious complementary information, since most probably it will not be possible to measure the full spectrum of new particles and their couplings through direct production. In particular, precision measurements and computations in the realm of flavor physics are expected to play a key role in constraining the unknown parameters of the Lagrangian of any NP model emerging from direct searches at the LHC. The aim of Working Group 2 was twofold: on the one hand, to provide a coherent up-to-date picture of the status of flavor physics before the start of the LHC; on the other hand, to initiate activities on the path towards integrating information on NP from high-p T and flavor data. This report is organized as follows: in Sect. 1, we give an overview of NP models, focusing on a few examples that have been discussed in some detail during the workshop, with a short description of the available computational tools for flavor observables in NP models. Section 2 contains a concise discussion of the main theoretical problem in flavor physics: the evaluation of the relevant hadronic matrix elements for weak decays. Section 3 contains a detailed discussion of NP effects in a set of flavor observables that we identified as "benchmark channels" for NP searches. The experimental prospects for flavor physics at future facilities are discussed in Sect. 4. Finally, Sect. 5 contains some assessments on the work done at the workshop and the prospects for future developments.
DOI: 10.1103/physrevd.94.011102
2016
Cited 127 times
Search for a muonic dark force at<i>BaBar</i>
Many models of physics beyond the standard model predict the existence of new Abelian forces with new gauge bosons mediating interactions between ``dark sectors'' and the standard model. We report a search for a dark boson ${Z}^{\ensuremath{'}}$ coupling only to the second and third generations of leptons in the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}{Z}^{\ensuremath{'}},{Z}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ using $514\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected by the BABAR experiment. No significant signal is observed for ${Z}^{\ensuremath{'}}$ masses in the range 0.212--10 GeV. Limits on the coupling parameter ${g}^{\ensuremath{'}}$ as low as $7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments.
DOI: 10.1088/1742-6596/1085/2/022008
2018
Cited 121 times
Machine Learning in High Energy Physics Community White Paper
Machine learning is an important applied research area in particle physics, beginning with applications to high-level physics analysis in the 1990s and 2000s, followed by an explosion of applications in particle and event identification and reconstruction in the 2010s. In this document we discuss promising future research and development areas in machine learning in particle physics with a roadmap for their implementation, software and hardware resource requirements, collaborative initiatives with the data science community, academia and industry, and training the particle physics community in data science. The main objective of the document is to connect and motivate these areas of research and development with the physics drivers of the High-Luminosity Large Hadron Collider and future neutrino experiments and identify the resource needs for their implementation. Additionally we identify areas where collaboration with external communities will be of great benefit.
DOI: 10.1088/1748-0221/17/01/p01005
2022
Cited 25 times
Design, construction and operation of the ProtoDUNE-SP Liquid Argon TPC
Abstract The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that was constructed and operated in the CERN North Area at the end of the H4 beamline. This detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment (DUNE), which will be constructed at the Sandford Underground Research Facility (SURF) in Lead, South Dakota, U.S.A. The ProtoDUNE-SP detector incorporates full-size components as designed for DUNE and has an active volume of 7 × 6 × 7.2 m 3 . The H4 beam delivers incident particles with well-measured momenta and high-purity particle identification. ProtoDUNE-SP's successful operation between 2018 and 2020 demonstrates the effectiveness of the single-phase far detector design. This paper describes the design, construction, assembly and operation of the detector components.
DOI: 10.1088/1748-0221/19/02/c02001
2024
Setups for eliminating static charge of the ATLAS18 strip sensors
Abstract Construction of the new all-silicon Inner Tracker (ITk), developed by the ATLAS collaboration to be able to track charged particles produced at the High-Luminosity LHC, started in 2020 and is expected to continue till 2028. The ITk detector will include 18,000 highly segmented and radiation hard n+-in-p silicon strip sensors (ATLAS18), which are being manufactured by Hamamatsu Photonics. Mechanical and electrical characteristics of produced sensors are measured upon their delivery at several institutes participating in a complex Quality Control (QC) program. The QC tests performed on each individual sensor check the overall integrity and quality of the sensor. During the QC testing of ATLAS18 strip sensors, an increased number of sensors that failed the electrical tests was observed. In particular, IV measurements indicated an early breakdown, while large areas containing several tens or hundreds of neighbouring strips with low interstrip isolation were identified by the Full strip tests, and leakage current instabilities were measured in a long-term leakage current stability setup. Moreover, a high surface electrostatic charge reaching a level of several hundreds of volts per inch was measured on a large number of sensors and on the plastic sheets, which mechanically protect these sensors in their paper envelopes. Accumulated data indicates a clear correlation between observed electrical failures and the sensor charge-up. To mitigate the above-described issues, the QC testing sites significantly modified the sensor handling procedures and introduced sensor recovery techniques based on irradiation of the sensor surface with UV light or application of intensive flows of ionized gas. In this presentation, we will describe the setups implemented by the QC testing sites to treat silicon strip sensors affected by static charge and evaluate the effectiveness of these setups in terms of improvement of the sensor performance.
DOI: 10.1103/physrevlett.123.021802
2019
Cited 44 times
Magnetic Monopole Search with the Full MoEDAL Trapping Detector in 13 TeV <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mi>p</mml:mi></mml:math> Collisions Interpreted in Photon-Fusion and Drell-Yan Production
MoEDAL is designed to identify new physics in the form of stable or pseudostable highly ionizing particles produced in high-energy Large Hadron Collider (LHC) collisions.Here we update our previous search for magnetic monopoles in Run 2 using the full trapping detector with almost four times more material and almost twice more integrated luminosity.For the first time at the LHC, the data were interpreted in terms of photon-fusion monopole direct production in addition to the Drell-Yan-like mechanism.The MoEDAL trapping detector, consisting of 794 kg of aluminum samples installed in the forward and lateral regions, was exposed to 4.0 fb -1 of 13 TeV proton-proton collisions at the LHCb interaction point and analyzed by searching for induced persistent currents after passage through a superconducting magnetometer.Magnetic charges equal to or above the Dirac charge are excluded in all samples.Monopole spins 0, ½, and 1 are considered and both velocity-independent and-dependent
DOI: 10.1038/s41586-021-04298-1
2022
Cited 20 times
Search for magnetic monopoles produced via the Schwinger mechanism
Electrically charged particles can be created by the decay of strong enough electric fields, a phenomenon known as the Schwinger mechanism1. By electromagnetic duality, a sufficiently strong magnetic field would similarly produce magnetic monopoles, if they exist2. Magnetic monopoles are hypothetical fundamental particles that are predicted by several theories beyond the standard model3-7 but have never been experimentally detected. Searching for the existence of magnetic monopoles via the Schwinger mechanism has not yet been attempted, but it is advantageous, owing to the possibility of calculating its rate through semi-classical techniques without perturbation theory, as well as that the production of the magnetic monopoles should be enhanced by their finite size8,9 and strong coupling to photons2,10. Here we present a search for magnetic monopole production by the Schwinger mechanism in Pb-Pb heavy ion collisions at the Large Hadron Collider, producing the strongest known magnetic fields in the current Universe11. It was conducted by the MoEDAL experiment, whose trapping detectors were exposed to 0.235 per nanobarn, or approximately 1.8 × 109, of Pb-Pb collisions with 5.02-teraelectronvolt center-of-mass energy per collision in November 2018. A superconducting quantum interference device (SQUID) magnetometer scanned the trapping detectors of MoEDAL for the presence of magnetic charge, which would induce a persistent current in the SQUID. Magnetic monopoles with integer Dirac charges of 1, 2 and 3 and masses up to 75 gigaelectronvolts per speed of light squared were excluded by the analysis at the 95% confidence level. This provides a lower mass limit for finite-size magnetic monopoles from a collider search and greatly extends previous mass bounds.
DOI: 10.1088/1748-0221/18/03/t03008
2023
Cited 7 times
Specifications and pre-production of n<sup>+</sup>-in-p large-format strip sensors fabricated in 6-inch silicon wafers, ATLAS18, for the Inner Tracker of the ATLAS Detector for High-Luminosity Large Hadron Collider
Abstract The ATLAS experiment is constructing new all-silicon inner tracking system for HL-LHC. The strip detectors cover the radial extent of 40 to 100 cm. A new approach is adopted to use p-type silicon material, making the readout in n + -strips, so-called n + -in-p sensors. This allows for enhanced radiation tolerance against an order of magnitude higher particle fluence compared to the LHC. To cope with varying hit rates and occupancies as a function of radial distance, there are two barrel sensor types, the short strips (SS) for the inner 2 and the long strips (LS) for the outer 2 barrel cylinders, respectively. The barrel sensors exhibit a square, 9.8 × 9.8 cm 2 , geometry, the largest possible sensor area from a 6-inch wafer. The strips are laid out in parallel with a strip pitch of 75.5 μm and 4 or 2 rows of strip segments. The strips are AC-coupled and biased via polysilicon resistors. The endcap sensors employ a “stereo-annulus” geometry exhibiting a skewed-trapezoid shapes with circular edges. They are designed in 6 unique shapes, R0 to R5, corresponding to progressively increasing radial extents and which allows them to fit within the petal geometry and the 6-inch wafer maximally. The strips are in fan-out geometry with an in-built rotation angle, with a mean pitch of approximately 75 μm and 4 or 2 rows of strip segments. The eight sensor types are labeled as ATLAS18xx where xx stands for SS, LS, and R0 to R5. According to the mechanical and electrical specifications, CAD files for wafer processing were laid out, following the successful designs of prototype barrel and endcap sensors, together with a number of optimizations. A pre-production was carried out prior to the full production of the wafers. The quality of the sensors is reviewed and judged excellent through the test results carried out by vendor. These sensors are used for establishing acceptance procedures and to evaluate their performance in the ATLAS collaboration, and subsequently for pre-production of strip modules and stave and petal structures.
DOI: 10.1103/physrevlett.118.031802
2017
Cited 43 times
Search for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>B</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mi>K</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>τ</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>τ</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:math> at the <i>BaBar</i> Experiment
We search for the rare flavor-changing neutral current process $B^{+}\rightarrow K^{+}τ^{+}τ^{-}$ using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the $Υ{(4S)}$ resonance, corresponds to a total integrated luminosity of 424 fb$^{-1}$ and to 471 million $B\overline{B}$ pairs. We reconstruct one $B$ meson, produced in the $Υ{(4S)}\rightarrow B^{+} B^{-}$ decay, in one of many hadronic decay modes and search for activity compatible with a $B^{+}\rightarrow K^{+} τ^{+}τ^{-}$ decay in the rest of the event. Each $τ$ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The measured branching fraction is ($1.31^{+0.66}_{-0.61}$( stat.)$^{+0.35}_{-0.25}$( sys.)$) \times 10^{-3}$ with an upper limit, at the 90\% confidence level, of $\mathcal{B}(B^{+}\rightarrow K^{+}τ^{+}τ^{-})$$&lt; 2.25\times 10^{-3}$.
DOI: 10.1103/physrevlett.123.091801
2019
Cited 36 times
Extraction of form Factors from a Four-Dimensional Angular Analysis of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mover accent="true"><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mrow></mml:mover><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mo>ℓ</mml:mo></mml:mrow><mml:mrow><mml:mo>−</mml:mo…
An angular analysis of the decay B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ}, ℓ∈{e,μ}, is reported using the full e^{+}e^{-} collision data set collected by the BABAR experiment at the ϒ(4S) resonance. One B meson from the ϒ(4S)→BB[over ¯] decay is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the dilepton mass squared, q^{2}, and three angles. The first unbinned fit to the full four-dimensional decay rate in the standard model is performed in the so-called Boyd-Grinstein-Lebed approach, which employs a generic q^{2} parametrization of the underlying form factors based on crossing symmetry, analyticity, and QCD dispersion relations for the amplitudes. A fit using the more model-dependent Caprini-Lellouch-Neubert (CLN) approach is performed as well. Our form factor shapes show deviations from previous fits based on the CLN parametrization. The latest form factors also provide an updated prediction for the branching fraction ratio R(D^{*})≡B(B[over ¯]→D^{*}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ})=0.253±0.005. Finally, using the well-measured branching fraction for the B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ} decay, a value of |V_{cb}|=(38.36±0.90)×10^{-3} is obtained that is consistent with the current world average for exclusive B[over ¯]→D^{(*)}ℓ^{-}ν[over ¯]_{ℓ} decays and remains in tension with the determination from inclusive semileptonic B decays to final states with charm.
DOI: 10.1103/physrevlett.126.071801
2021
Cited 23 times
First Search for Dyons with the Full MoEDAL Trapping Detector in 13 TeV <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mi>p</mml:mi></mml:math> Collisions
The MoEDAL trapping detector consists of approximately 800 kg of aluminum volumes.It was exposed during run 2 of the LHC program to 6.46 fb -1 of 13 TeV proton-proton collisions at the LHCb interaction point.Evidence for dyons (particles with electric and magnetic charge) captured in the trapping detector was sought by passing the aluminum volumes comprising the detector through a superconducting quantum interference device (SQUID) magnetometer.The presence of a trapped dyon would be signaled by a persistent current induced in the SQUID magnetometer.On the basis of a Drell-Yan production model, we exclude dyons with a magnetic charge ranging up to five Dirac charges (5g D ) and an electric charge up to 200 times the fundamental electric charge for mass limits in the range 870-3120 GeV and also monopoles with magnetic charge up to and including 5g D with mass limits in the range 870-2040 GeV.
DOI: 10.1016/j.nima.2014.06.086
2014
Cited 37 times
Development of n+-in-p large-area silicon microstrip sensors for very high radiation environments – ATLAS12 design and initial results
We have been developing a novel radiation-tolerant n+-in-p silicon microstrip sensor for very high radiation environments, aiming for application in the high luminosity large hadron collider. The sensors are fabricated in 6 in., p-type, float-zone wafers, where large-area strip sensor designs are laid out together with a number of miniature sensors. Radiation tolerance has been studied with ATLAS07 sensors and with independent structures. The ATLAS07 design was developed into new ATLAS12 designs. The ATLAS12A large-area sensor is made towards an axial strip sensor and the ATLAS12M towards a stereo strip sensor. New features to the ATLAS12 sensors are two dicing lines: standard edge space of 910 μm and slim edge space of 450 μm, a gated punch-through protection structure, and connection of orphan strips in a triangular corner of stereo strips. We report the design of the ATLAS12 layouts and initial measurements of the leakage current after dicing and the resistivity of the wafers.
DOI: 10.1016/j.physletb.2018.05.069
2018
Cited 37 times
Search for magnetic monopoles with the MoEDAL forward trapping detector in 2.11 fb−1 of 13 TeV proton–proton collisions at the LHC
We update our previous search for trapped magnetic monopoles in LHC Run 2 using nearly six times more integrated luminosity and including additional models for the interpretation of the data. The MoEDAL forward trapping detector, comprising 222~kg of aluminium samples, was exposed to 2.11~fb$^{-1}$ of 13 TeV proton-proton collisions near the LHCb interaction point and analysed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges equal to the Dirac charge or above are excluded in all samples. The results are interpreted in Drell-Yan production models for monopoles with spins 0, 1/2 and 1: in addition to standard point-like couplings, we also consider couplings with momentum-dependent form factors. The search provides the best current laboratory constraints for monopoles with magnetic charges ranging from two to five times the Dirac charge.
DOI: 10.1103/physrevd.104.072002
2021
Cited 21 times
Light meson spectroscopy from Dalitz plot analyses of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>η</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math> decays to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow><mml:mi>η</mml:mi></mml:mrow><mml:mrow><mml:mo>′</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mi>K</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>K</mml:mi><mml:mo>−</mml:mo></mml:msup></mml…
We study the processes $\gamma \gamma \to \eta_c \to \eta' K^+ K^-$, $\eta' \pi^+ \pi^-$, and $\eta \pi^+ \pi^-$ using a data sample of 519 $fb^{-1}$ recorded with the BaBar detector operating at the SLAC PEP-II asymmetric-energy $e^+e^-$ collider at center-of-mass energies at and near the $\Upsilon(nS)$ ($n = 2,3,4$) resonances. This is the first observation of the decay $\eta_c \to \eta' K^+ K^-$ and we measure the branching fraction $\Gamma(\eta_c \to \eta' K^+ K^-)/(\Gamma(\eta_c \to \eta' \pi^+ \pi^-)=0.644\pm 0.039_{\rm stat}\pm 0.032_{\rm sys}$. Significant interference is observed between $\gamma \gamma \to \eta_c\to \eta \pi^+ \pi^-$ and the non-resonant two-photon process $\gamma \gamma \to \eta \pi^+ \pi^-$. A Dalitz plot analysis is performed of $\eta_c$ decays to $\eta' K^+ K^-$, $\eta' \pi^+ \pi^-$, and $\eta \pi^+ \pi^-$. Combined with our previous analysis of $\eta_c \to K \bar K \pi$, we measure the $K^*_0(1430)$ parameters and the ratio between its $\eta' K$ and $\pi K$ couplings. The decay $\eta_c \to \eta' \pi^+ \pi^-$ is dominated by the $f_0(2100)$ resonance, also observed in $J/\psi$ radiative decays. A new $a_0(1700) \to \eta \pi$ resonance is observed in the $\eta_c \to \eta \pi^+ \pi^-$ channel. We also compare $\eta_c$ decays to $\eta$ and $\eta'$ final states in association with scalar mesons as they relate to the identification of the scalar glueball.
DOI: 10.1103/physrevd.98.112012
2018
Cited 22 times
Measurement of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>cos</mml:mi><mml:mrow><mml:mn>2</mml:mn><mml:mi>β</mml:mi></mml:mrow></mml:math> in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>B</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mi>D</mml:mi><mml:mrow><mml:mo mathvariant="bold" stretchy="false">(</mml:mo><mml:mo>*</mml:mo><mml:mo mathvariant="bold" stretchy="false…
We report measurements of sin2β and cos2β using a time-dependent Dalitz plot analysis of B0→D(*)h0 with D→KS0π+π− decays, where the light unflavored and neutral hadron h0 is a π0, η, or ω meson. The analysis uses a combination of the final data sets of the BaBar and Belle experiments containing 471×106 and 772×106 BB¯ pairs collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We measure sin2β=0.80±0.14(stat)±0.06(syst)±0.03(model) and cos2β=0.91±0.22(stat)±0.09(syst)±0.07(model). The result for the direct measurement of the angle is β=(22.5±4.4(stat)±1.2(syst)±0.6(model))°. The last quoted uncertainties are due to the composition of the D0→KS0π+π− decay amplitude model, which is newly established by a Dalitz plot amplitude analysis of a high-statistics e+e−→cc¯ data sample as part of this analysis. We find the first evidence for cos2β>0 at the level of 3.7 standard deviations. The measurement excludes the trigonometric multifold solution π/2−β=(68.1±0.7)° at the level of 7.3 standard deviations and therefore resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle. The hypothesis of β=0° is ruled out at the level of 5.1 standard deviations, and thus CP violation is observed in B0→D(*)h0 decays. The measurement assumes no direct CP violation in B0→D(*)h0 decays.3 MoreReceived 17 April 2018DOI:https://doi.org/10.1103/PhysRevD.98.112012Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)PropertiesCP violationParticles & Fields
DOI: 10.1016/j.nima.2016.04.035
2016
Cited 19 times
Charge collection and field profile studies of heavily irradiated strip sensors for the ATLAS inner tracker upgrade
The ATLAS group has evaluated the charge collection in silicon microstrip sensors irradiated up to a fluence of 1×1016 neq/cm2, exceeding the maximum of 1.6×1015 neq/cm2 expected for the strip tracker during the high luminosity LHC (HL-LHC) period including a safety factor of 2. The ATLAS12, n+-on-p type sensor, which is fabricated by Hamamatsu Photonics (HPK) on float zone (FZ) substrates, is the latest barrel sensor prototype. The charge collection from the irradiated 1×1 cm2 barrel test sensors has been evaluated systematically using penetrating β-rays and an Alibava readout system. The data obtained at different measurement sites are compared with each other and with the results obtained from the previous ATLAS07 design. The results are very consistent, in particular, when the deposit charge is normalized by the sensor's active thickness derived from the edge transient current technique (edge-TCT) measurements. The measurements obtained using β-rays are verified to be consistent with the measurements using an electron beam. The edge-TCT is also effective for evaluating the field profiles across the depth. The differences between the irradiated ATLAS07 and ATLAS12 samples have been examined along with the differences among the samples irradiated with different radiation sources: neutrons, protons, and pions. The studies of the bulk properties of the devices show that the devices can yield a sufficiently large signal for the expected fluence range in the HL-LHC, thereby acting as precision tracking sensors.
DOI: 10.1103/physrevlett.128.131802
2022
Cited 8 times
Search for an Axionlike Particle in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi></mml:math> Meson Decays
Axionlike particles (ALPs) are predicted in many extensions of the standard model, and their masses can naturally be well below the electroweak scale. In the presence of couplings to electroweak bosons, these particles could be emitted in flavor-changing B meson decays. We report herein a search for an ALP, a, in the reaction B^{±}→K^{±}a, a→γγ using data collected by the BABAR experiment at SLAC. No significant signal is observed, and 90% confidence level upper limits on the ALP coupling to electroweak bosons are derived as a function of ALP mass, improving current constraints by several orders of magnitude in the range 0.175 GeV<m_{a}<4.78 GeV.
DOI: 10.1103/physrevd.95.072001
2017
Cited 17 times
Measurement of the inclusive electron spectrum from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi></mml:math> meson decays and determination of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo stretchy="false">|</mml:mo><mml:msub><mml:mi>V</mml:mi><mml:mrow><mml:mi>u</mml:mi><mml:mi>b</mml:mi></mml:mrow></mml:msub><mml:mo stretchy="false">|</mml:mo></mml:math>
Based on the full BABAR data sample of 466.5 million $B\overline{B}$ pairs, we present measurements of the electron spectrum from semileptonic $B$ meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed $B\ensuremath{\rightarrow}{X}_{u}e\ensuremath{\nu}$ decays from the CKM-favored $B\ensuremath{\rightarrow}{X}_{c}e\ensuremath{\nu}$ decays, and from various other backgrounds, and determine the total semileptonic branching fraction $\mathcal{B}(B\ensuremath{\rightarrow}Xe\ensuremath{\nu})=(10.34\ifmmode\pm\else\textpm\fi{}{0.04}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.2{6}_{\mathrm{syst}})%$, averaged over ${B}^{\ifmmode\pm\else\textpm\fi{}}$ and ${B}^{0}$ mesons. We determine the spectrum and branching fraction for charmless $B\ensuremath{\rightarrow}{X}_{u}e\ensuremath{\nu}$ decays and extract the CKM element $|{V}_{ub}|$, by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above $2.1\text{ }\text{ }\mathrm{GeV}/c$ is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element $|{V}_{ub}|$ are presented, with the lower limit on the electron momentum varied from $0.8\text{ }\text{ }\mathrm{GeV}/c$ to the kinematic endpoint. We determine $|{V}_{ub}|$ using each of these different calculations and find, $|{V}_{ub}|=(3.794\ifmmode\pm\else\textpm\fi{}{0.107}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.219\text{ }\mathrm{SF}}^{+0.292}{\text{ }}_{\ensuremath{-}0.068\text{ }\text{theory}}^{+0.078})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (De Fazio and Neubert), $(4.563\ifmmode\pm\else\textpm\fi{}{0.126}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.208\text{ }\mathrm{SF}}^{+0.230}{\text{ }}_{\ensuremath{-}0.163\text{ }\text{theory}}^{+0.162})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (Bosch, Lange, Neubert, and Paz), $(3.959\ifmmode\pm\else\textpm\fi{}{0.104}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.154\text{ }\mathrm{SF}}^{+0.164}{\text{ }}_{\ensuremath{-}0.079\text{ }\text{theory}}^{+0.042})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (Gambino, Giordano, Ossola, and Uraltsev), $(3.848\ifmmode\pm\else\textpm\fi{}{0.108}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.070\text{ }\text{theory}}^{+0.084})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.
DOI: 10.48550/arxiv.2402.01568
2024
Doping Liquid Argon with Xenon in ProtoDUNE Single-Phase: Effects on Scintillation Light
Doping of liquid argon TPCs (LArTPCs) with a small concentration of xenon is a technique for light-shifting and facilitates the detection of the liquid argon scintillation light. In this paper, we present the results of the first doping test ever performed in a kiloton-scale LArTPC. From February to May 2020, we carried out this special run in the single-phase DUNE Far Detector prototype (ProtoDUNE-SP) at CERN, featuring 770 t of total liquid argon mass with 410 t of fiducial mass. The goal of the run was to measure the light and charge response of the detector to the addition of xenon, up to a concentration of 18.8 ppm. The main purpose was to test the possibility for reduction of non-uniformities in light collection, caused by deployment of photon detectors only within the anode planes. Light collection was analysed as a function of the xenon concentration, by using the pre-existing photon detection system (PDS) of ProtoDUNE-SP and an additional smaller set-up installed specifically for this run. In this paper we first summarize our current understanding of the argon-xenon energy transfer process and the impact of the presence of nitrogen in argon with and without xenon dopant. We then describe the key elements of ProtoDUNE-SP and the injection method deployed. Two dedicated photon detectors were able to collect the light produced by xenon and the total light. The ratio of these components was measured to be about 0.65 as 18.8 ppm of xenon were injected. We performed studies of the collection efficiency as a function of the distance between tracks and light detectors, demonstrating enhanced uniformity of response for the anode-mounted PDS. We also show that xenon doping can substantially recover light losses due to contamination of the liquid argon by nitrogen.
DOI: 10.48550/arxiv.2402.15682
2024
MoEDAL search in the CMS beam pipe for magnetic monopoles produced via the Schwinger effect
We report on a search for magnetic monopoles (MMs) produced in ultraperipheral Pb--Pb collisions during Run-1 of the LHC. The beam pipe surrounding the interaction region of the CMS experiment was exposed to 174.29 $\mathrm{\mu}$b$^{-1}$ of Pb--Pb collisions at 2.76 TeV center-of-mass energy per collision in December 2011. It was scanned by the MoEDAL experiment using a SQUID magnetometer to search for trapped MMs. No MM signal was observed. The two distinctive features of this search are the use of a trapping volume very close to the collision point and ultra-high magnetic fields generated during the heavy-ion run that could produce MMs via the Schwinger effect. These two advantages allowed setting the first reliable, world-leading mass limits on MMs with high magnetic charge. In particular, the established limits are the strongest available in the range between 2 and 45 Dirac units, excluding MMs with masses of up to 80 GeV at 95% confidence level.
DOI: 10.1016/j.nima.2024.169446
2024
Identification and recovery of ATLAS18 strip sensors with high surface static charge
DOI: 10.1017/cbo9781139342810
2013
Cited 18 times
Statistical Data Analysis for the Physical Sciences
Data analysis lies at the heart of every experimental science. Providing a modern introduction to statistics, this book is ideal for undergraduates in physics. It introduces the necessary tools required to analyse data from experiments across a range of areas, making it a valuable resource for students. In addition to covering the basic topics, the book also takes in advanced and modern subjects, such as neural networks, decision trees, fitting techniques and issues concerning limit or interval setting. Worked examples and case studies illustrate the techniques presented, and end-of-chapter exercises help test the reader's understanding of the material.
DOI: 10.1103/physrevlett.115.121604
2015
Cited 15 times
First Observation of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi><mml:mi>P</mml:mi></mml:math>Violation in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mover accent="true"><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mrow></mml:mover></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:msubsup><…
We report a measurement of the time-dependent CP asymmetry of B[over ¯]^{0}→D_{CP}^{(*)}h^{0} decays, where the light neutral hadron h^{0} is a π^{0}, η, or ω meson, and the neutral D meson is reconstructed in the CP eigenstates K^{+}K^{-}, K_{S}^{0}π^{0}, or K_{S}^{0}ω. The measurement is performed combining the final data samples collected at the ϒ(4S) resonance by the BABAR and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6} BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6} BB[over ¯] pairs recorded by the Belle detector. We measure the CP asymmetry parameters -η_{f}S=+0.66±0.10(stat)±0.06(syst) and C=-0.02±0.07(stat)±0.03(syst). These results correspond to the first observation of CP violation in B[over ¯]^{0}→D_{CP}^{(*)}h^{0} decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.
DOI: 10.48550/arxiv.1807.02876
2018
Cited 15 times
Machine Learning in High Energy Physics Community White Paper
Machine learning has been applied to several problems in particle physics research, beginning with applications to high-level physics analysis in the 1990s and 2000s, followed by an explosion of applications in particle and event identification and reconstruction in the 2010s. In this document we discuss promising future research and development areas for machine learning in particle physics. We detail a roadmap for their implementation, software and hardware resource requirements, collaborative initiatives with the data science community, academia and industry, and training the particle physics community in data science. The main objective of the document is to connect and motivate these areas of research and development with the physics drivers of the High-Luminosity Large Hadron Collider and future neutrino experiments and identify the resource needs for their implementation. Additionally we identify areas where collaboration with external communities will be of great benefit.
DOI: 10.1016/j.nima.2016.03.056
2016
Cited 14 times
Study of surface properties of ATLAS12 strip sensors and their radiation resistance
A radiation hard n+-in-p micro-strip sensor for the use in the Upgrade of the strip tracker of the ATLAS experiment at the High Luminosity Large Hadron Collider (HL-LHC) has been developed by the "ATLAS ITk Strip Sensor collaboration" and produced by Hamamatsu Photonics. Surface properties of different types of end-cap and barrel miniature sensors of the latest sensor design ATLAS12 have been studied before and after irradiation. The tested barrel sensors vary in "punch-through protection" (PTP) structure, and the end-cap sensors, whose stereo-strips differ in fan geometry, in strip pitch and in edge strip ganging options. Sensors have been irradiated with proton fluences of up to 1×1016 neq/cm2, by reactor neutron fluence of 1×1015 neq/cm2 and by gamma rays from 60Co up to dose of 1 MGy. The main goal of the present study is to characterize the leakage current for micro-discharge breakdown voltage estimation, the inter-strip resistance and capacitance, the bias resistance and the effectiveness of PTP structures as a function of bias voltage and fluence. It has been verified that the ATLAS12 sensors have high breakdown voltage well above the operational voltage which implies that different geometries of sensors do not influence their stability. The inter-strip isolation is a strong function of irradiation fluence, however the sensor performance is acceptable in the expected range for HL-LHC. New gated PTP structure exhibits low PTP onset voltage and sharp cut-off of effective resistance even at the highest tested radiation fluence. The inter-strip capacitance complies with the technical specification required before irradiation and no radiation-induced degradation was observed. A summary of ATLAS12 sensors tests is presented including a comparison of results from different irradiation sites. The measured characteristics are compared with the previous prototype of the sensor design, ATLAS07.
DOI: 10.1016/j.nuclphysbps.2013.06.015
2013
Cited 15 times
Standard Model updates and new physics analysis with the Unitarity Triangle fit
We present the summer 2012 update of the Unitarity Triangle (UT) analysis performed by the UTfit Collaboration within the Standard Model (SM) and beyond. The increased accuracy on several of the fundamental constraints is now enhancing some of the tensions amongst and within the constraint themselves. In particular, the long standing tension between exclusive and inclusive determinations of the Vub and Vcb CKM matrix elements is now playing a major role. Then we present the generalisation the UT analysis to investigate new physics (NP) effects, updating the constraints on NP contributions to ΔF=2 processes. In the NP analysis, both CKM and NP parameters are fitted simultaneously to obtain the possible NP effects in any specific sector. Finally, based on the NP constraints, we derive upper bounds on the coefficients of the most general ΔF=2 effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of NP that contributes to these low-energy effective interactions.
DOI: 10.1103/physrevd.93.012005
2016
Cited 12 times
Measurement of theI=1/2Kπ S-wave amplitude from Dalitz plot analyses ofηc→KK¯πin two-photon interactions
We study the processes $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ and $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ using a data sample of $519\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider at center-of-mass energies at and near the $\mathrm{\ensuremath{\Upsilon}}(nS)$ ($n=2$, 3, 4) resonances. We observe ${\ensuremath{\eta}}_{c}$ decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the $I=1/2$ $K\ensuremath{\pi}\text{ }\mathcal{S}$-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of $1.5\text{ }\text{ }\mathrm{GeV}/{c}^{2}$. In contrast, the amplitudes show very marked differences. The data require the presence of a new ${a}_{0}(1950)$ resonance with parameters $m=1931\ifmmode\pm\else\textpm\fi{}14\ifmmode\pm\else\textpm\fi{}22\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $\mathrm{\ensuremath{\Gamma}}=271\ifmmode\pm\else\textpm\fi{}22\ifmmode\pm\else\textpm\fi{}29\text{ }\text{ }\mathrm{MeV}$.
DOI: 10.1103/physrevd.93.112014
2016
Cited 12 times
Measurement of the neutral<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>D</mml:mi></mml:mrow></mml:math>meson mixing parameters in a time-dependent amplitude analysis of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><…
We perform the first measurement on the ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$ mixing parameters using a time-dependent amplitude analysis of the decay ${D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$. The data were recorded with the BABAR detector at center-of-mass energies at and near the $\ensuremath{\Upsilon}(4S)$ resonance, and correspond to an integrated luminosity of approximately $468.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. The neutral $D$ meson candidates are selected from ${D}^{*}(2010{)}^{+}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\pi}}_{s}^{+}$ decays where the flavor at the production is identified by the charge of the low-momentum pion, ${\ensuremath{\pi}}_{s}^{+}$. The measured mixing parameters are $x=(1.5\ifmmode\pm\else\textpm\fi{}1.2\ifmmode\pm\else\textpm\fi{}0.6)%$ and $y=(0.2\ifmmode\pm\else\textpm\fi{}0.9\ifmmode\pm\else\textpm\fi{}0.5)%$, where the quoted uncertainties are statistical and systematic, respectively.
DOI: 10.1103/physrevlett.121.261801
2018
Cited 12 times
First Evidence for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>cos</mml:mi><mml:mn>2</mml:mn><mml:mi>β</mml:mi><mml:mo>&gt;</mml:mo><mml:mn>0</mml:mn></mml:math> and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity
We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] pairs recorded by the Belle detector. The results of the measurement are sin2β=0.80±0.14(stat)±0.06(syst)±0.03(model) and cos2β=0.91±0.22(stat)±0.09(syst)±0.07(model). The result for the direct measurement of the angle β of the CKM Unitarity Triangle is β=[22.5±4.4(stat)±1.2(syst)±0.6(model)]°. The measurement assumes no direct CP violation in B^{0}→D^{(*)}h^{0} decays. The quoted model uncertainties are due to the composition of the D^{0}→K_{S}^{0}π^{+}π^{-} decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics e^{+}e^{-}→cc[over ¯] data sample. CP violation is observed in B^{0}→D^{(*)}h^{0} decays at the level of 5.1 standard deviations. The significance for cos2β>0 is 3.7 standard deviations. The trigonometric multifold solution π/2-β=(68.1±0.7)° is excluded at the level of 7.3 standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.
DOI: 10.1016/j.nima.2016.04.044
2016
Cited 11 times
Evaluation of the performance of irradiated silicon strip sensors for the forward detector of the ATLAS Inner Tracker Upgrade
The upgrade to the High-Luminosity LHC foreseen in about ten years represents a great challenge for the ATLAS inner tracker and the silicon strip sensors in the forward region. Several strip sensor designs were developed by the ATLAS collaboration and fabricated by Hamamatsu in order to maintain enough performance in terms of charge collection efficiency and its uniformity throughout the active region. Of particular attention, in the case of a stereo-strip sensor, is the area near the sensor edge where shorter strips were ganged to the complete ones. In this work the electrical and charge collection test results on irradiated miniature sensors with forward geometry are presented. Results from charge collection efficiency measurements show that at the maximum expected fluence, the collected charge is roughly halved with respect to the one obtained prior to irradiation. Laser measurements show a good signal uniformity over the sensor. Ganged strips have a similar efficiency as standard strips.
DOI: 10.1016/j.nima.2016.03.042
2016
Cited 10 times
Detailed studies of full-size ATLAS12 sensors
The "ATLAS ITk Strip Sensor Collaboration" R&D group has developed a second iteration of single-sided n+-in-p type micro-strip sensors for use in the tracker upgrade of the ATLAS experiment at the High-Luminosity (HL) LHC. The full size sensors measure approximately 97×97mm2 and are designed for tolerance against the 1.1×1015neq/cm2 fluence expected at the HL-LHC. Each sensor has 4 columns of 1280 individual 23.9mm long channels, arranged at 74.5μm pitch. Four batches comprising 120 sensors produced by Hamamatsu Photonics were evaluated for their mechanical, and electrical bulk and strip characteristics. Optical microscopy measurements were performed to obtain the sensor surface profile. Leakage current and bulk capacitance properties were measured for each individual sensor. For sample strips across the sensor batches, the inter-strip capacitance and resistance as well as properties of the punch-through protection structure were measured. A multi-channel probecard was used to measure leakage current, coupling capacitance and bias resistance for each individual channel of 100 sensors in three batches. The compiled results for 120 unirradiated sensors are presented in this paper, including summary results for almost 500,000 strips probed. Results on the reverse bias voltage dependence of various parameters and frequency dependence of tested capacitances are included for validation of the experimental methods used. Comparing results with specified values, almost all sensors fall well within specification.
2014
Cited 9 times
Standard Model updates and new physics analysis with the Unitarity Triangle fit
We present here the update of the Unitarity Triangle (UT) analysis performed by the UTfit Collaboration within the Standard Model (SM) and beyond. Continuously updated flavour results contribute to improving the precision of several constraints and through the global fit of the CKM parameters and the SM predictions. We also extend the UT analysis to investigate new physics (NP) effects on $\Delta F=2$ processes. Finally, based on the NP constraints, we derive upper bounds on the coefficients of the most general $\Delta F=2$ effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of NP that contributes to these low-energy effective interactions.
DOI: 10.1140/epjc/s10052-022-10608-2
2022
Cited 4 times
Search for highly-ionizing particles in pp collisions at the LHC’s Run-1 using the prototype MoEDAL detector
A search for highly electrically charged objects (HECOs) and magnetic monopoles is presented using 2.2 fb-1 of p - p collision data taken at a centre of mass energy (ECM) of 8 TeV by the MoEDAL detector during LHC's Run-1. The data were collected using MoEDAL's prototype Nuclear Track Detector array and the Trapping Detector array. The results are interpreted in terms of Drell-Yan pair production of stable HECO and monopole pairs with three spin hypotheses (0, 1/2 and 1). The search provides constraints on the direct production of magnetic monopoles carrying one to four Dirac magnetic charges (4gD) and with mass limits ranging from 590 GeV/c^2 to 1 TeV/c^2. Additionally, mass limits are placed on HECOs with charge in the range 10e to 180e, where e is the charge of an electron, for masses between 30 GeV/c^2 and 1 TeV/c^2.
DOI: 10.1140/epjc/s10052-022-10791-2
2022
Cited 4 times
Separation of track- and shower-like energy deposits in ProtoDUNE-SP using a convolutional neural network
Liquid argon time projection chamber detector technology provides high spatial and calorimetric resolutions on the charged particles traversing liquid argon. As a result, the technology has been used in a number of recent neutrino experiments, and is the technology of choice for the Deep Underground Neutrino Experiment (DUNE). In order to perform high precision measurements of neutrinos in the detector, final state particles need to be effectively identified, and their energy accurately reconstructed. This article proposes an algorithm based on a convolutional neural network to perform the classification of energy deposits and reconstructed particles as track-like or arising from electromagnetic cascades. Results from testing the algorithm on data from ProtoDUNE-SP, a prototype of the DUNE far detector, are presented. The network identifies track- and shower-like particles, as well as Michel electrons, with high efficiency. The performance of the algorithm is consistent between data and simulation.
DOI: 10.1088/1748-0221/17/12/c12013
2022
Cited 4 times
ATLAS ITk strip sensor quality control procedures and testing site qualification
Abstract The high-luminosity upgrade of the Large Hadron Collider, scheduled to become operational in 2029, requires the replacement of the ATLAS Inner Detector with a new all-silicon Inner Tracker. Radiation hard n + -in-p micro-strip silicon sensors were developed by the ATLAS Inner Tracker strip collaboration and are produced by Hamamatsu Photonics K.K. Production of the total amount of 22000 strip sensors has started in 2020 and will continue until 2025. The ATLAS strip sensor collaboration has the responsibility to monitor the quality of the fabricated devices by performing detailed measurements of individual sensor characteristics and by comparing the obtained results with the tests done by the manufacturer. Dedicated Quality Control procedures were developed to check whether the delivered large-format sensors adhere to the ATLAS specifications. The institutes performing the Quality Control testing of the pre-production and production ATLAS ITk strip sensors had to initially be qualified for multiple high-throughput tests by successfully completing the Site Qualification process. The Quality Control procedures and the qualification process are described in this paper.
DOI: 10.1140/epjc/s10052-023-11733-2
2023
Reconstruction of interactions in the ProtoDUNE-SP detector with Pandora
Abstract The Pandora Software Development Kit and algorithm libraries provide pattern-recognition logic essential to the reconstruction of particle interactions in liquid argon time projection chamber detectors. Pandora is the primary event reconstruction software used at ProtoDUNE-SP, a prototype for the Deep Underground Neutrino Experiment far detector. ProtoDUNE-SP, located at CERN, is exposed to a charged-particle test beam. This paper gives an overview of the Pandora reconstruction algorithms and how they have been tailored for use at ProtoDUNE-SP. In complex events with numerous cosmic-ray and beam background particles, the simulated reconstruction and identification efficiency for triggered test-beam particles is above 80% for the majority of particle type and beam momentum combinations. Specifically, simulated 1 GeV/ c charged pions and protons are correctly reconstructed and identified with efficiencies of 86.1 $$\pm 0.6$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>±</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> </mml:math> % and 84.1 $$\pm 0.6$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>±</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> </mml:math> %, respectively. The efficiencies measured for test-beam data are shown to be within 5% of those predicted by the simulation.
DOI: 10.1103/physrevlett.122.081802
2019
Cited 8 times
Observation of the Decay <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>D</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mi>K</mml:mi><mml:mo>−</mml:mo></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:math>
We report the observation of the rare charm decay ${D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{e}^{+}{e}^{\ensuremath{-}}$, based on $468\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of ${e}^{+}{e}^{\ensuremath{-}}$ annihilation data collected at or close to the center-of-mass energy of the $\mathrm{\ensuremath{\Upsilon}}(4\mathrm{S})$ resonance with the BABAR detector at the SLAC National Accelerator Laboratory. We find the branching fraction in the invariant mass range $0.675&lt;m({e}^{+}{e}^{\ensuremath{-}})&lt;0.875\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ of the electron-positron pair to be $\mathcal{B}({D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{e}^{+}{e}^{\ensuremath{-}})=\phantom{\rule{0ex}{0ex}}(4.0\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}6}$, where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty in the branching fraction of the decay ${D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ used as a normalization mode. The significance of the observation corresponds to 9.7 standard deviations including systematic uncertainties. This result is consistent with the recently reported ${D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ branching fraction, measured in the same invariant mass range, and with the value expected in the standard model. In a set of regions of $m({e}^{+}{e}^{\ensuremath{-}})$, where long-distance effects are potentially small, we determine a 90% confidence level upper limit on the branching fraction $\mathcal{B}({D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{e}^{+}{e}^{\ensuremath{-}})&lt;3.1\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}6}$.
DOI: 10.48550/arxiv.0810.1312
2008
Cited 10 times
Proceedings of SuperB Workshop VI: New Physics at the Super Flavor Factory
The sixth SuperB Workshop was convened in response to questions posed by the INFN Review Committee, evaluating the SuperB project at the request of INFN. The working groups addressed the capability of a high-luminosity flavor factory that can gather a data sample of 50 to 75 /ab in five years to elucidate New Physics phenomena unearthed at the LHC. This report summarizes the results of the Workshop.
DOI: 10.1016/j.nima.2012.10.084
2013
Cited 7 times
Recent developments on CMOS MAPS for the SuperB Silicon Vertex Tracker
In the design of the Silicon Vertex Tracker for the high luminosity SuperB collider, very challenging requirements are set by physics and background conditions on its innermost Layer0: small radius (about 1.5 cm), resolution of 10–15μm in both coordinates, low material budget <1%X0, and the ability to withstand a background hit rate of several tens of MHz/cm2. Thanks to an intense R&D program the development of Deep NWell CMOS MAPS (with the ST Microelectronics 130 nm process) has reached a good level of maturity and allowed for the first time the implementation of thin CMOS sensors with similar functionalities as in hybrid pixels, such as pixel-level sparsification and fast time stamping. Further MAPS performance improvements are currently under investigation with two different approaches: the INMAPS CMOS process, featuring a quadruple well and a high resistivity substrate, and 3D CMOS MAPS, realized with vertical integration technology. In both cases specific features of the processes chosen can improve charge collection efficiency, with respect to a standard DNW MAPS design, and allow to implement a more complex in-pixel logic in order to develop a faster readout architecture. Prototypes of MAPS matrix, suitable for application in the SuperB Layer0, have been realized with the INMAPS 180 nm process and the 130 nm Chartered/Tezzaron 3D process and results of their characterization will be presented in this paper.
DOI: 10.1103/physrevd.95.092005
2017
Cited 7 times
Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:msubsup><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mi>s</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msubsup><mml:msup><mml:mrow…
The processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{0}$ and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}\ensuremath{\eta}$ are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using $454\text{ }\text{ }{\text{fb}}^{\ensuremath{-}1}$ of data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from ${K}^{*0}(K\ensuremath{\pi}{)}^{0}$, ${K}^{*}(892{)}^{\ifmmode\pm\else\textpm\fi{}}(K\ensuremath{\pi}{)}^{\ensuremath{\mp}}$, and ${K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\rho}}^{\ensuremath{\mp}}$ are studied. The $J/\ensuremath{\psi}$ is observed in all of these channels, and corresponding branching fractions are measured.
DOI: 10.1016/j.nima.2016.04.019
2016
Cited 6 times
Embedded pitch adapters: A high-yield interconnection solution for strip sensors
A proposal to fabricate large area strip sensors with integrated, or embedded, pitch adapters is presented for the End-cap part of the Inner Tracker in the ATLAS experiment. To implement the embedded pitch adapters, a second metal layer is used in the sensor fabrication, for signal routing to the ASICs. Sensors with different embedded pitch adapters have been fabricated in order to optimize the design and technology. Inter-strip capacitance, noise, pick-up, cross-talk, signal efficiency, and fabrication yield have been taken into account in their design and fabrication. Inter-strip capacitance tests taking into account all channel neighbors reveal the important differences between the various designs considered. These tests have been correlated with noise figures obtained in full assembled modules, showing that the tests performed on the bare sensors are a valid tool to estimate the final noise in the full module. The full modules have been subjected to test beam experiments in order to evaluate the incidence of cross-talk, pick-up, and signal loss. The detailed analysis shows no indication of cross-talk or pick-up as no additional hits can be observed in any channel not being hit by the beam above 170 mV threshold, and the signal in those channels is always below 1% of the signal recorded in the channel being hit, above 100 mV threshold. First results on irradiated mini-sensors with embedded pitch adapters do not show any change in the interstrip capacitance measurements with only the first neighbors connected.
DOI: 10.48550/arxiv.1408.3813
2014
Cited 6 times
C, P, and CP asymmetry observables based on triple product asymmetries
Triple product asymmetries have been used to probe CP violation in $K$, $D$, and B decays. Here we review the interpretation of those asymmetries, and note that it is possible to construct twelve measurable triple product asymmetries for the decay of a particle into a four body final state. Eight of these asymmetries are introduced here and nine have never been measured before. These can be used to systematically test C, P, and CP symmetries in decays to four body final states. In particular we note that these asymmetries can be used to study symmetry invariance in Higgs, $Z^0$, top-quark, and hadron decay (both baryon and meson) as well as for $\tau^\pm$ decay at production threshold.
DOI: 10.1088/1475-7516/2021/10/065
2021
Cited 5 times
Searching for solar KDAR with DUNE
The observation of 236 MeV muon neutrinos from kaon-decay-at-rest (KDAR) originating in the core of the Sun would provide a unique signature of dark matter annihilation. Since excellent angle and energy reconstruction are necessary to detect this monoenergetic, directional neutrino flux, DUNE with its vast volume and reconstruction capabilities, is a promising candidate for a KDAR neutrino search. In this work, we evaluate the proposed KDAR neutrino search strategies by realistically modeling both neutrino-nucleus interactions and the response of DUNE. We find that, although reconstruction of the neutrino energy and direction is difficult with current techniques in the relevant energy range, the superb energy resolution, angular resolution, and particle identification offered by DUNE can still permit great signal/background discrimination. Moreover, there are non-standard scenarios in which searches at DUNE for KDAR in the Sun can probe dark matter interactions.
DOI: 10.1016/j.nima.2009.05.046
2009
Cited 7 times
Interaction-point phase-space characterization using single-beam and luminous-region measurements at PEP-II
We present an extensive experimental characterization of the e± phase space at the interaction point of the SLAC PEP-II B-Factory, that combines a detailed mapping of luminous-region observables using the BABAR detector, with stored-beam measurements by accelerator techniques.
DOI: 10.1103/physrevd.90.094028
2014
Cited 4 times
Bounding hadronic uncertainties in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>c</mml:mi><mml:mo stretchy="false">→</mml:mo><mml:mi>u</mml:mi></mml:math>decays
Time-dependent $CP$ asymmetry measurements in $D\ensuremath{\rightarrow}{h}^{+}{h}^{\ensuremath{-}}$ decays, where $h=\ensuremath{\pi}$ or $\ensuremath{\rho}$ can, in principal, be used to constrain the angle ${\ensuremath{\beta}}_{c}$ of the $cu$ unitarity triangle up to theoretical uncertainties. Here we discuss the theoretical uncertainty from penguin contributions that can be investigated through the use of isospin analyses. We show that uncertainty from penguin pollution on a measurement of ${\ensuremath{\beta}}_{c}$ (or alternatively the mixing phase) in ${D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ (${\ensuremath{\rho}}^{+}{\ensuremath{\rho}}^{\ensuremath{-}}$) decays is 2.7\ifmmode^\circ\else\textdegree\fi{} (4.6\ifmmode^\circ\else\textdegree\fi{}). We also comment on the applicability of this method to ${D}^{0}\ensuremath{\rightarrow}\ensuremath{\rho}\ensuremath{\pi}$ decays for which measurements of weak phases with a precision below the one degree level may be possible.
DOI: 10.1016/j.nima.2013.05.023
2013
Cited 4 times
First tests of CHERWELL, a Monolithic Active Pixel Sensor: A CMOS Image Sensor (CIS) using 180nm technology
The Cherwell is a 4T CMOS sensor in 180 nm technology developed for the detection of charged particles. Here, the different test structures on the sensor will be described and first results from tests on the reference pixel variant are shown. The sensors were shown to have a noise of 12 e− and a signal to noise up to 150 in 55Fe.
DOI: 10.22323/1.291.0096
2017
Cited 4 times
Latest results from Utfit
Flavour physics represents a unique test bench for the Standard Model (SM).New analyses performed at the LHC experiments are now providing unprecedented insights into Cabibbo-Kobayashi-Maskawa (CKM) metrology and new evidences for rare decays.The CKM picture can provide very precise SM predictions through global analyses.We present here the results of the latest global SM analysis performed by the UTfit collaboration including all the most updated inputs from experiments, lattice QCD and phenomenological calculations.In addition, the Unitarity Triangle (UT) analysis can be used to constrain the parameter space in possible new physics (NP) scenarios.Assuming NP, all of the available experimental and theoretical information on ∆F = 2 processes is combined using a model-independent parametrisation.We determine the allowed NP contributions in the kaon, D, B d , and B s sectors and, in various NP scenarios, we translate them into bounds for the NP scale as a function of NP couplings.
DOI: 10.22323/1.314.0205
2017
Cited 4 times
Unitarity Triangle Analysis and D meson mixing in the Standard Model and Beyond
Flavour physics represents a unique test bench for the Standard Model (SM).New analyses performed at the LHC experiments are now providing unprecedented insights into CKM metrology and new evidences for rare decays.The CKM picture can provide very precise SM predictions through global analyses.We present here the results of the latest global SM analysis performed by the UTfit collaboration including all the most updated inputs from experiments, lattice QCD and phenomenological calculations.In addition, we update the analysis of D meson mixing: we derive constraints on the parameters M 12 , Γ 12 and Φ 12 that describe D meson mixing using all available data, allowing for CP violation.Finally, the Unitarity Triangle (UT) analysis can be used to constrain the parameter space in possible new physics (NP) scenarios.All of the available experimental and theoretical information on ∆F = 2 processes is reinterpreted including a modelindependent NP parametrisation.We determine the allowed NP contributions in the kaon, D, B d , and B s sectors and, in various NP scenarios, we translate them into bounds for the NP scale as a function of NP couplings.
DOI: 10.22323/1.282.0149
2017
Cited 4 times
Unitarity Triangle analysis beyond the Standard Model from UTfit
The Unitarity Triangle (UT) analysis can be used to constrain the parameter space in possible new physics (NP) scenarios.We present here an update of the UT analysis beyond the Standard Model (SM) by the UTfit collaboration.Assuming NP, all of the available experimental and theoretical information on ∆F = 2 processes is combined using a model-independent parametrisation.We determine the allowed NP contributions in the kaon, D, B d , and B s sectors and, in various NP scenarios, we translate them into bounds for the NP scale as a function of NP couplings.
DOI: 10.1088/1742-6596/762/1/012052
2016
Cited 3 times
Support Vector Machines and Generalisation in HEP
We review the concept of support vector machines (SVMs) and discuss examples of their use. One of the benefits of SVM algorithms, compared with neural networks and decision trees is that they can be less susceptible to over fitting than those other algorithms are to over training. This issue is related to the generalisation of a multivariate algorithm (MVA); a problem that has often been overlooked in particle physics. We discuss cross validation and how this can be used to improve the generalisation of a MVA in the context of High Energy Physics analyses. The examples presented use the Toolkit for Multivariate Analysis (TMVA) based on ROOT and describe our improvements to the SVM functionality and new tools introduced for cross validation within this framework.
DOI: 10.48550/arxiv.1302.4191
2013
Cited 3 times
Neutral meson tests of time-reversal symmetry invariance
The laws of quantum physics can be studied under the mathematical operation T that inverts the direction of time. Strong and electromagnetic forces are known to be invariant under temporal inversion, however the weak force is not. The BaBar experiment recently exploited the quantum-correlated production of pairs of B0 mesons to show that T is a broken symmetry. Here we show that it is possible to perform a wide range of tests of quark flavour changing processes under T in order to validate the Standard Model of particle physics covering b to u, d, s, and c transitions as well as c to u, d and s transitions using entangled B and D pairs created in Y(4S) and psi(3770) decays. We also note that pseudoscalar decays to two spin one particle final states provide an additional set of CP filter bases to use for T violation tests.
DOI: 10.1016/j.nima.2012.11.036
2013
Cited 3 times
The front-end chip of the SuperB SVT detector
The asymmetric e+e− collider SuperB is designed to deliver a high luminosity, greater than 1036cm−2s−1, with moderate beam currents and a reduced center of mass boost with respect to earlier B-Factories. The innermost detector is the Silicon Vertex Tracker which is made of 5 layers of double sided silicon strip sensors plus a layer 0, that can be equipped with short striplets detectors in a first phase of the experiment. In order to achieve an overall track reconstruction efficiency above 98% it is crucial to optimize both analog and digital readout circuits. The readout architecture being developed for the front-end chips will be able to cope with the very high rates expected in the first layer. The digital readout will be optimized to be fully efficient for hit rates up to 2 MHz/strip, including large margins on the maximum expected background rates, but can potentially accommodate higher rates with a proper tuning of the buffer depth. The readout is based on a triggered architecture where each of the 128 strip channel is provided with a dedicated digital buffer. Each buffer collects the digitized charge information by means of a 4-bit TOT, storing it in conjunction with the related time stamp. The depth of buffers was dimensioned considering the expected trigger latency and hit rate including suitable safety margins. Every buffer is connected to a highly parallelized circuit handling the trigger logic, rejecting expired data in the buffers and channeling the parallel stream of triggered hits to the common output of the chip. The presented architecture has been modeled by HDL language and investigated with a Monte Carlo hit generator emulating the analog front-end behavior. The simulations showed that even applying the highest stressing conditions, about 2 MHz per strip, the efficiency of the digital readout remained above 99.8%.
DOI: 10.1088/1742-6596/898/7/072046
2017
Cited 3 times
Machine Learning Developments in ROOT
ROOT is a software framework for large-scale data analysis that provides basic and advanced statistical methods used by high-energy physics experiments. It includes machine learning tools from the ROOT-integrated Toolkit for Multivariate Analysis (TMVA). We present several recent developments in TMVA, including a new modular design, new algorithms for pre-processing, cross-validation, hyperparameter-tuning, deep-learning and interfaces to other machine-learning software packages. TMVA is additionally integrated with Jupyter, making it accessible with a browser.
DOI: 10.1088/1742-6596/898/7/072021
2017
Cited 3 times
Support vector machines and generalisation in HEP
We review the concept of Support Vector Machines (SVMs) and discuss examples of their use in a number of scenarios. Several SVM implementations have been used in HEP and we exemplify this algorithm using the Toolkit for Multivariate Analysis (TMVA) implementation. We discuss examples relevant to HEP including background suppression for $H\to\tau^+\tau^-$ at the LHC with several different kernel functions. Performance benchmarking leads to the issue of generalisation of hyper-parameter selection. The avoidance of fine tuning (over training or over fitting) in MVA hyper-parameter optimisation, i.e. the ability to ensure generalised performance of an MVA that is independent of the training, validation and test samples, is of utmost importance. We discuss this issue and compare and contrast performance of hold-out and k-fold cross-validation. We have extended the SVM functionality and introduced tools to facilitate cross validation in TMVA and present results based on these improvements.
2021
Cited 3 times
First experimental search for production of magnetic monopoles via the Schwinger mechanism
Schwinger showed that electrically-charged particles can be produced in a strong electric field by quantum tunnelling through the Coulomb barrier. By electromagnetic duality, if magnetic monopoles (MMs) exist, they would be produced by the same mechanism in a sufficiently strong magnetic field. Unique advantages of the Schwinger mechanism are that its rate can be calculated using semiclassical techniques without relying on perturbation theory, and the finite MM size and strong MM-photon coupling are expected to enhance their production. Pb-Pb heavy-ion collisions at the LHC produce the strongest known magnetic fields in the current Universe, and this article presents the first search for MM production by the Schwinger mechanism. It was conducted by the MoEDAL experiment during the 5.02 TeV/nucleon heavy-ion run at the LHC in November 2018, during which the MoEDAL trapping detectors (MMTs) were exposed to 0.235 nb$^{-1}$ of Pb-Pb collisions. The MMTs were scanned for the presence of magnetic charge using a SQUID magnetometer. MMs with Dirac charges 1$g_D$$\leq$$g$$\leq$ 3$g_D$ and masses up to 75 GeV/c$^2$ were excluded by the analysis. This provides the first lower mass limit for finite-size MMs from a collider search and significantly extends previous mass bounds.
DOI: 10.1016/j.nima.2012.10.086
2013
Beam test results for the SuperB-SVT thin striplet detector
The baseline detector option for the first layer of the SuperB Silicon Vertex Tracker (SVT) is a high resistivity double-sided silicon device with short strips (striplets) at 45° angle to the detector's edge. A prototype was tested with a 120 GeV/c pion beam in September 2011 at the SPS-H6 test-beam line at CERN. In this paper studies on efficiency, resolution and cluster size are reported.
2023
Search for Highly-Ionizing Particles in pp Collisions During LHC Run-2 Using the Full MoEDAL Detector
DOI: 10.48550/arxiv.2312.03130
2023
The DUNE Far Detector Vertical Drift Technology, Technical Design Report
DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals.
DOI: 10.1016/j.nuclphysbps.2010.12.019
2010
Unitarity Triangle Analysis: An Update
We present the update of the Unitarity Triangle analysis performed by the UTfit Collaboration within the Standard Model and beyond. Within the Standard Model, we find an overall consistency among the constraints, with some tension between the fit prediction and the experimental measurement of BR ( B → τ ν ) , sin 2 β and e K . Generalising the analysis beyond the Standard Model, we allow for New Physics effects in all Δ F = 2 processes simultanously. We obtain constraints on the parameters of the Cabibbo-Kobayashi-Maskawa matrix together with the New Physics ones. We find that a deviation from the Standard Model at the 3.1σ level in the B s - B ¯ s mixing phase is confirmed by the present update, which includes the new DO result on the dimuon charge asymmetry. However the new CDF measurement of ϕ s is not included yet as the experimental likelihood is not publicly available.
DOI: 10.48550/arxiv.1710.09644
2017
Unitarity Triangle Analysis in the Standard Model and Beyond
Flavour physics represents a unique test bench for the Standard Model (SM). New analyses performed at the LHC experiments are now providing unprecedented insights into CKM metrology and new evidences for rare decays. The CKM picture can provide very precise SM predictions through global analyses. We present here the results of the latest global SM analysis performed by the UTfit collaboration including all the most updated inputs from experiments, lattice QCD and phenomenological calculations. In addition, the Unitarity Triangle (UT) analysis can be used to constrain the parameter space in possible new physics (NP) scenarios. We update here also the UT analysis beyond the SM by the UTfit collaboration. All of the available experimental and theoretical information on $ΔF=2$ processes is reinterpreted including a model-independent NP parametrisation. We determine the allowed NP contributions in the kaon, $D$, $B_d$, and $B_s$ sectors and, in various NP scenarios, we translate them into bounds for the NP scale as a function of NP couplings.
DOI: 10.22323/1.291.0143
2017
Neutral charm mixing results from the Utfit collaboration
We update here the analysis of D meson mixing including the latest experimental results.We derive constraints on the parameters M 12 , Γ 12 and Φ 12 that describe D meson mixing using all available data, allowing for CP violation.We also provide posterior distributions for observable parameters appearing in D physics.
DOI: 10.22323/1.282.0554
2017
Unitarity Triangle analysis in the Standard Model from the UTfit collaboration
Flavour physics represents a unique test bench for the Standard Model (SM).New analyses performed at the LHC experiments are now providing unprecedented insights into Cabibbo-Kobayashi-Maskawa (CKM) metrology and new evidences for rare decays.The CKM picture can provide very precise SM predictions through global analyses.We present here the results of the latest global SM analysis performed by the UTfit collaboration including all the most updated inputs from experiments, lattice QCD and phenomenological calculations.
2008
Results from the B Factories
These proceedings are based on lectures given at the Helmholtz International Summer School Heavy Quark Physics at the Bogoliubov Laboratory of Theoretical Physics, Dubna, Russia, during August 2008. I review the current status of CP violation in B meson decays from the B factories. These results can be used, along with measurements of the sides of the Unitarity Triangle, to test the CKM mechanism. In addition I discuss experimental studies of B decays to final states with `spin-one' particles.
DOI: 10.1021/acsami.0c22210
2021
Solution-Processed Donor–Acceptor Poly(3-hexylthiophene):Phenyl-C<sub>61</sub>-butyric Acid Methyl Ester Diodes for Low-Voltage α Particle Detection
Diodes fabricated using a blend of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (6–80 μm thick) as an organic semiconductor component achieved consistent 4 MeV α particle detection. Current–voltage characteristics and current–time measurements were obtained under α irradiation and in its absence. Steady-state and transient (time-of-flight) photoconduction measurements were additionally performed. Low-bias (<20 V) α particle detection gain-efficiency products of order 10–2 were measured. The α particle detection was achieved reproducibly, reversibly, and repeatably in different devices of varying organic semiconductor layer thicknesses using both the steady-state and time-dependent (dynamic) diode responses. Conductive gain, due to trapped electrons, increased the α particle gain-efficiency product in both forward and reverse bias conditions as well as increasing steady-state photoconduction. The device thickness was optimized to maximize the gain-efficiency product by matching the penetration depth of the α particle, obtained by modeling, to the organic semiconductor layer thickness. Very high confidence α particle detection was achieved (with signal-to-noise ratios exceeding 20) under optimized device dimensions and drive conditions. Hecht function fitting of the gain-efficiency product versus electric field data returns mobility-lifetime products of order 10–6–10–7 cm2 V–1. This work demonstrates that solution-processed organic semiconductor diodes are viable for low-voltage α particle detection.
DOI: 10.1016/j.nima.2013.05.170
2013
Latest results of the R&amp;D on CMOS MAPS for the Layer0 of the SuperB SVT
Physics and high background conditions set very challenging requirements on readout speed, material budget and resolution for the innermost layer of the SuperB Silicon Vertex Tracker operated at the full luminosity. Monolithic Active Pixel Sensors (MAPS) are very appealing in this application since the thin sensitive region allows grinding the substrate to tens of microns. Deep N-Well MAPS, developed in the ST 130 nm CMOS technology, achieved in-pixel sparsification and fast time stamping. Further improvements are being explored with an intense R&D program, including both vertical integration and 2D MAPS with the INMAPS quadruple well. We present the results of the characterization with IR laser, radioactive sources and beam of several chips produced with the 3D (Chartered/Tezzaron) process. We have also studied prototypes exploiting the features of the quadruple well and the high resistivity epitaxial layer of the INMAPS 180 nm process. Promising results from an irradiation campaign with neutrons on small matrices and other test-structures, as well as the response of the sensors to high energy charged tracks are presented.
DOI: 10.1016/j.nima.2013.06.070
2013
Advances in the development of pixel detector for the SuperB Silicon Vertex Tracker
The latest advances in the design and characterization of several pixel sensors developed to satisfy the very demanding requirements of the innermost layer of the SuperB Silicon Vertex Tracker will be presented in this paper. The SuperB machine is an electron positron collider operating at the ϒ(4S) peak to be built in the very near future by the Cabibbo Lab consortium. A pixel detector based on extremely thin, radiation hard devices able to cope with rate in the tens of MHz/cm2 range will be the optimal solution for the upgrade of the inner layer of the SuperB tracking system. At present several options with different levels of maturity are being investigated to understand advantages and potential issues of the different technologies: thin hybrid pixels, Deep N-Well CMOS MAPS, INMAPS CMOS MAPS featuring a quadruple well and high resistivity substrates and CMOS MAPS realized with Vertical Integration technology. The newest results from beam test, the outcomes of the radiation damage studies and the laboratory characterization of the latest prototypes will be reported.
DOI: 10.1016/j.nima.2011.04.013
2011
Design study for a next generation B factory pixel vertex detector
We present a conceptual design for a low-mass, all-pixel vertex detector using the CMOS quadruple well INMAPS process, capable of working in the very high luminosities exceeding 1036 cm−2 s−1 that can be expected at the next generation e+e− B Factories. We concentrate on the vertexing requirements necessary for time-dependent measurements that are also relevant to searches for new physics beyond the Standard Model. We investigate different configurations and compare with the existing baseline designs for the SuperB and BaBar experiments.
DOI: 10.1103/physrevlett.128.091804
2022
Search for Lepton Flavor Violation in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">ϒ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>3</mml:mn><mml:mi>S</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo mathvariant="bold">±</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>μ</mml:mi></mml:mrow><mml:mrow><mml:mo>∓</mml:mo></…
We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state. We look for the LFV decay ϒ(3S)→e^{±}μ^{∓} in a sample of 118 million ϒ(3S) mesons from 27 fb^{-1} of data collected with the BABAR detector at the SLAC PEP-II e^{+}e^{-} collider operating with a 10.36 GeV center-of-mass energy. No evidence for a signal is found, and we set a limit on the branching fraction B[ϒ(3S)→e^{±}μ^{∓}]<3.6×10^{-7} at 90% C. L. This result can be interpreted as a limit Λ_{NP}/g_{NP}^{2}>80 TeV on the energy scale Λ_{NP} divided by the coupling-squared g_{NP}^{2} of relevant new physics (NP).
DOI: 10.1017/cbo9781139342810.002
2013
Introduction
The use of statistical data analysis in physics means different things to different people. The reason for this is that most problems are different, and so someone concentrating on areas where the experimental data collected are relatively straightforward to analyse will naturally tend to use techniques that are simpler than those required for a more complicated problem or for a sparse data sample. Ultimately we all need to use statistical methods in order to translate data into some measure of a physical observable. This book will discuss a number of different concepts and techniques in order of increasing complexity. Before embarking on a discussion of statistics the remainder of this chapter introduces three common experimental problems encountered by students studying physics: (i) using a pendulum to measure acceleration due to gravity (Section 1.1), (ii) testing the validity of Ohm's law for a conductor (Section 1.2), and (iii) measuring the half-life of a radioactive isotope (Section 1.3). These examples rely on material covered in Chapters 4 through 7 and Chapter 9. Readers who appreciate the context of material in the remainder of this book may wish to skip forward to the next chapter.
DOI: 10.1103/physrevlett.119.202003
2017
Measurement of the D*(2010)+−D+ Mass Difference
We measure the mass difference, Δm_{+}, between the D^{*}(2010)^{+} and the D^{+} using the decay chain D^{*}(2010)^{+}→D^{+}π^{0} with D^{+}→K^{-}π^{+}π^{+}. The data were recorded with the BABAR detector at center-of-mass energies at and near the ϒ(4S) resonance, and correspond to an integrated luminosity of approximately 468 fb^{-1}. We measure Δm_{+}=(140 601.0±6.8[stat]±12.9[syst]) keV. We combine this result with a previous BABAR measurement of Δm_{0}≡m(D^{*}(2010)^{+})-m(D^{0}) to obtain Δm_{D}=m(D^{+})-m(D^{0})=(4824.9±6.8[stat]±12.9[syst]) keV. These results are compatible with and approximately five times more precise than the Particle Data Group averages.
DOI: 10.48550/arxiv.1008.1938
2010
Design Study for a SuperB Pixel Vertex Detector
We present a conceptual design for a low-mass, all pixel vertex detector using the CMOS quadruple well INMAPS process, capable of working in the very high luminosities exceeding 10^36 /cm^2 /sec that can be expected at the next generation e+e- B factories. We concentrate on the vertexing requirements necessary for time-dependent measurements that are also relevant to searches for new physics beyond the Standard Model. We investigate different configurations and compare with the baseline designs for the SuperB and BaBar experiments.
2006
COMBINED PHASE SPACE CHARACTERIZATION AT THE PEP-II IP USING SINGLE-BEAM AND LUMINOUS-REGION MEASUREMENTS ∗
We present a novel method to characterize the e ± phase space at the IP of the SLAC B-factory, that combines single-beam measurements with a detailed mapping of luminous-region observables. Transverse spot sizes are determined in the two rings with synchrotron-light monitors and extrapolated to the IP using measured lattice functions. The specific luminosity, which is proportional to the inverse product of the overlap IP beam sizes, is continuously monitored using radiative–Bhabha events. The spatial variation of the luminosity and of the transverseboost distribution of the colliding e ± , are measured using e + e − → μ + μ − events reconstructed in the BABAR detector. The combination of these measurements provide constraints on the emittances, horizontal and vertical spot sizes, angular divergences and β functions of both beams at the IP during physics data-taking. Preliminary results of this combined spot-size analysis are confronted with independent measurements of IP β-functions and overlap IP beam sizes at low beam current.
DOI: 10.48550/arxiv.physics/0607087
2006
Combined phase space characterization at the PEP-II IP using single-beam and luminous-region measurements
We present a novel method to characterize the e+/- phase space at the IP of the SLAC B-factory, that combines single-beam measurements with a detailed mapping of luminous-region observables. Transverse spot sizes are determined in the two rings with synchrotron-light monitors and extrapolated to the IP using measured lattice functions. The specific luminosity, which is proportional to the inverse product of the overlap IP beam sizes, is continuously monitored using radiative-Bhabha events. The spatial variation of the luminosity and of the transverse-boost distribution of the colliding e+/-, are measured using e+ e- --&gt; mu+ mu- events reconstructed in the BaBar detector. The combination of these measurements provide constraints on the emittances, horizontal and vertical spot sizes, angular divergences and beta functions of both beams at the IP during physics data-taking. Preliminary results of this combined spot-size analysis are confronted with independent measurements of IP beta-functions and overlap IP beam sizes at low beam current.
DOI: 10.48550/arxiv.2108.01902
2021
Design, construction and operation of the ProtoDUNE-SP Liquid Argon TPC
The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that was constructed and operated in the CERN North Area at the end of the H4 beamline. This detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment (DUNE), which will be constructed at the Sandford Underground Research Facility (SURF) in Lead, South Dakota, USA. The ProtoDUNE-SP detector incorporates full-size components as designed for DUNE and has an active volume of $7\times 6\times 7.2$~m$^3$. The H4 beam delivers incident particles with well-measured momenta and high-purity particle identification. ProtoDUNE-SP's successful operation between 2018 and 2020 demonstrates the effectiveness of the single-phase far detector design. This paper describes the design, construction, assembly and operation of the detector components.
DOI: 10.48550/arxiv.hep-ex/0408069
2004
Measurement of CP-Asymmetries for the Decays B+/- to D_cp Kstar+/- with the BABAR Detector
Using a sample of 227 million $\Upsilon(4S) \to B \bar{B}$ events collected with the $BABAR$ detector at the PEP-II $B$ Factory in 1999--2004, we study $B^- \to D^0 K^*(892)^-$ decays where $K^{*-} \to K^0_S \pi^-$ and $D^0 \to K^-\pi^+, K^- \pi^+ \pi^0, K^-\pi^+ \pi^+ \pi^-$ (non-CP final states), $K^+ K^-, \pi^+ \pi^- (CP+$ eigenstates), $K^0_S~\pi^0, K^0_S \phi$ and $K^0_S \omega (CP-$ eigenstates). The partial rate charge asymmetries $\mathcal{A}_{CP}$ and the ratios $\mathcal{R}_{CP}$ defined in the literature as the sum of the $B^+$ and $B^-$ partial rates to a charged $K^*$ and a $D^0 CP$-eigenstate divi ded by the $B \to D^0 K^*$ decay rate, %of the \ensuremath{\Bu}\xspace\xspace m \ensuremath{\to}\xspace \Dcp \ensuremath{K^*}\xspacepm branch ing fractions summed over %\B charge to the \ensuremath{B^-}\xspace \xspace\ensuremath{\to}\xspace \ensuremath{D^0}\xspace \ensu remath{K^{*-}}\xspace branching fraction are sensitive to the angle $\gamma$ of the CKM unitarity triangle. We measure: \mathcal{A}_{CP+} &=&-0.09 \pm 0.20 (stat.) \pm 0.06 (syst.) \mathcal{A}_{CP-} &=& -0.33 \pm 0.34 (stat.) \pm 0.10 (syst.) (+1.15 \pm 0.12) \cdot (\mathcal{A}_{CP-} - \mathcal{A}_{CP+}) \mathcal{R}_{CP+} &=& +1.77 \pm 0.37 (stat.) \pm 0.12 (syst.) \mathcal{R}_{CP-} &=& +0.76 \pm 0.29 (stat.) \pm 0.06 (syst.) ^{- 0.04}_{-\ 0.14} The third uncertainty quoted for the CP- measurements reflects possible interference effects in the final states with $\phi$ and $\omega$ resonances. All results are preliminary.
DOI: 10.1016/s0920-5632(03)90608-6
2003
CP asymmetries and charmless branching fractions with BABAR
A summary of recent results of searches for direct CP violation and measurements of charmless B-meson decay branching fractions with the BABAR detector is presented.
DOI: 10.22323/1.116.0039
2016
Global fit to CKM data (UTfit)
2016
Rare B decays at ATLAS
2014
First Results from Cherwell, a Monolithic Active Pixel Sensor for Particle Physics
DOI: 10.22323/1.180.0507
2014
Intrinsic n-well MAPS for particle physics
Cherwell is a CMOS Monolithic Active Pixel Sensor (MAPS) developed for digital calorimetry and charged particle tracking applications.Here, we outline the initial tests carried out to characterise the performance of Cherwell, give details of the test beam carried out at CERN and include the first results from this analysis.Three variations of the chip were tested; Type A, a high resistivity, low noise sensor, Type B, a standard resisivity, low noise sensor and Type C, a standard resistivity, standard noise sensor.The sensors yield an average RMS noise value per pixel of 9.6 e -and a gain of 0.17 ADCs/e -.The sensor efficiencies are 99.89% for Type A, 99.77% for Type B and 99.73% for Type C, with an average efficiency of 99.80%.
DOI: 10.48550/arxiv.1506.04246
2015
C, P, and CP asymmetry observables based on triple product asymmetries
The discrete symmetries C, P and CP are known to be violated by the weak interaction. It is possible to probe the breaking of these symmetries using asymmetries constructed from triple products based on the decay of some particle M to a four body final state. These proceedings discuss the full set of possible asymmetries that can be probed and applications to various measurement scenarios, focusing mostly on charm mesons and baryons. The ramifications of what can be learned from such measurements are also discussed.
DOI: 10.48550/arxiv.1411.7233
2014
Standard Model updates and new physics analysis with the Unitarity Triangle fit
We present here the update of the Unitarity Triangle (UT) analysis performed by the UTfit Collaboration within the Standard Model (SM) and beyond. Continuously updated flavour results contribute to improving the precision of several constraints and through the global fit of the CKM parameters and the SM predictions. We also extend the UT analysis to investigate new physics (NP) effects on $\Delta F=2$ processes. Finally, based on the NP constraints, we derive upper bounds on the coefficients of the most general $\Delta F=2$ effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of NP that contributes to these low-energy effective interactions.
2011
The Physics Programme at SuperB
SuperB is a next generation high luminosity $e^+e^-$ collider that will be built at the Cabibbo Laboratory, Tor Vergata, in Italy. The physics goals of this experiment are to search for signs of physics beyond the Standard Model through precision studies of rare or forbidden processes. While the name suggests that $B$ physics is the main goal, this experiment is a Super Flavour Factory, and precision measurements of $B_{u,d,s}$, $D$, $\tau$, $\Upsilon$, and $\psi(3770)$ decays as well as spectroscopy and exotica searches form part of a broad physics programme. In addition to searching for new physics (NP) in the form of heavy particles, or violations of laws of physics, data from SuperB will be able to perform precision tests of the Standard Model. I will briefly review of some highlights of the SuperB physics programme.
2011
Time-dependent CP asymmetries in charm decays
The CKM paradigm has been tested thoroughly over the last 40 years in both the neutral $K$ and $B$ systems. The recent discovery of neutral charm meson mixing has prompted the search for CP violation in $D$ decays. We discuss the prospects of performing time-dependent CP asymmetry measurements at facilities either taking data or under construction. Such measurements can (i) provide precision determinations of the charm mixing phase, and (ii) be used to probe for possible new physics effects (and perhaps ultimately constrain the CKM paradigm). We propose the use of the time-dependent asymmetry measurement of $D^0 \to K^+K^-$ decays to measure the phase of charm mixing, where existing experiments that are either under construction or taking data should be able to reach a precision of $<1.5^\circ$, and to use the phase difference between $D^0 \to K^+K^-$ and $D^0 \to \pi^+\pi^-$ decays to constrain the angle $\beta_c$ of the $cu$ unitarity triangle up to theoretical uncertainties from long distance and loop contributions. A large phase difference measured between these modes would indicate new physics.
2013
T symmetry invariance tests in neutral meson decays
We outline how the time-reversal symmetry T can be systematically used to test the Kobayashi-Maskawa mechanism embedded in the CKM matrix using pairs of B mesons created at the Upsilon(4S) and pairs of D mesons from psi(3770).
DOI: 10.1017/cbo9781139342810.017
2013
References
A summary is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.
DOI: 10.1017/cbo9781139342810.007
2013
Uncertainty and errors
A summary is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.
DOI: 10.1017/cbo9781139342810.013
2013
Probability density functions
A summary is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.
DOI: 10.1017/cbo9781139342810.014
2013
Numerical integration methods
A summary is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.
DOI: 10.1017/cbo9781139342810.005
2013
Visualising and quantifying the properties of data
A summary is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.
2011
The unitarity triangle analysis within and beyond the standard model
2013
Testing the quantum arrow of time in weak decays
The laws of quantum physics can be studied under the mathematical operation T that inverts the direction of time. Strong and electromagnetic forces are known to be invariant under temporal inversion, however the weak force is not. The BaBar experiment recently exploited the quantum-correlated production of pairs of B0 mesons to show that T is a broken symmetry. Here we show that it is possible to perform a wide range of tests of quark flavour changing processes under T in order to validate the Standard Model of particle physics covering b to u, d, s, and c transitions as well as c to u, d and s transitions using entangled B and D pairs created in Y(4S) and psi(3770) decays. We also note that pseudoscalar decays to two spin one particle final states provide an additional set of CP filter bases to use for T violation tests.
DOI: 10.22323/1.128.0019
2011
Unitarity Triangle Analysis within and beyond the SM
We present the status of the Unitarity Triangle Analysis (UTA) performed by the UTfit Collaboration, with experimental and theoretical inputs updated for the last summer conferences.Several analyses are presented, corresponding to different assumptions for the theoretical model, that is either the Standard Model, or Minimal Flavour Violation or completely generic New Physics.
2012
Search for dark-sector Higgs and gauge bosons at BABAR
DOI: 10.1017/cbo9781139342810.004
2013
Probability
The probability of something occurring is the quantification of the chance of observing a particular outcome given a single event. The event itself may be the result of a single experiment, or one single data point collected by an un-repeatable experiment. We refer to a single event or an ensemble of events as data, and the way we refer to data implies if data is singular or plural. If we quantify the probability of a repeatable experiment, then this understanding can be used to make predictions of the outcomes of future experiments. We cannot predict the outcome of a given experiment with certainty; however, we can assign a level of confidence to our predictions that incorporates the uncertainty from our previous knowledge and any information of the limitations of the experiment to be performed.
DOI: 10.1017/cbo9781139342810.011
2013
Multivariate analysis
Consider a data sample Ω described by the set of variables x that is composed of two (or more) populations. Often we are faced with the task of trying to identify or separate one sub-sample from the other (as these are different classes or types of events). In practice it is often not possible to completely separate samples of one class A from another class B as was seen in the case of likelihood fits to data. There are a number of techniques that can be used in order to try and optimally identify or separate a sub-sample of data from the whole, and some of these are described below. Each of the techniques described has its own benefits and disadvantages, and the final choice of the ‘optimal’ solution of how to separate A and B can require subjective input from the analyst. In general this type of situation requires the use of multivariate analysis (MVA).
DOI: 10.1017/cbo9781139342810.006
2013
Useful distributions
This chapter introduces four important distributions that can be used to describe a variety of situations. The first distribution encountered is that of the binomial distribution (Section 5.2). This is used to understand problems where the possible outcomes are binary, and usually categorised in terms of success and failure. For example, one can consider the situation of either detecting of failing to detect a particle passing through some apparatus as a binary event. The detection efficiency in this particular problem is the parameter p of the binomial distribution. Typically one finds that p ~ 1 when working with efficient detectors. The Poisson distribution (Section 5.3) can be used to understand rare events where the total number of trials is not necessarily known, and the distribution depends on only the number of observed events and a single parameter λ that is both the mean and variance of the distribution. For example, the Poisson distribution can be used to describe the uncertainties on the content of each bin in Figure 1.2, which is a topic discussed in more detail in Chapter 7. The third distribution discussed here is the Gaussian distribution (Section 5.4). This plays a significant role in describing the uncertainties on measurements where the number of data are large. Finally the X2 distribution is introduced in Section 5.5.
DOI: 10.1017/cbo9781139342810.010
2013
Fitting
A summary is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.
DOI: 10.1017/cbo9781139342810.009
2013
Hypothesis testing
Up until now we have discussed how to define a measurement in terms of a central value, uncertainties, and units, as well as how to extend these concepts to encompass confidence levels (both one- and two-sided). A related aspect of performing a measurement is to test a theory or, as it is usually phrased, a hypothesis. For example, consider the case where a theorist writes a paper proposing the existence of some effect that can be tested via some physical process. It is then down to an experimentalist to develop a method that can be used to test the validity of that theory. In this example the default hypothesis (usually referred to as the null hypothesis and often denoted by H0) would be that the theory is valid, and the experimenter would then embark on a measurement that could be used to test the null hypothesis.
DOI: 10.1017/cbo9781139342810.012
2013
Glossary
This section summarises many of the terms used in this book. A brief description of the meaning of each term is given, and where appropriate a cross reference to the corresponding section in the text is suggested for further reading.