E. Paganis

A measurement of the proton structure function F_2(x,Q^2) is presented in the kinematic range 0.045 GeV^2 < Q^2 < 0.65 GeV^2 and 6*10^{-7} < x < 1*10^{-3}. The results were obtained using a data sample corresponding to an integrated luminosity of 3.9pb^-1 in e^+p reactions recorded with the ZEUS detector at HERA. Information from a silicon-strip tracking detector, installed in front of the small electromagnetic calorimeter used to measure the energy of the final-state positron at small scattering angles, together with an enhanced simulation of the hadronic final state, has permitted the extension of the kinematic range beyond that of previous measurements. The uncertainties in F_2 are typically less than 4%. At the low Q^2 values of the present measurement, the rise of F_2 at low x is slower than observed in HERA data at higher Q^2 and can be described by Regge theory with a constant logarithmic slope. The dependence of F_2 on Q^2 is stronger than at higher Q^2 values, approaching, at the lowest Q^2 values of this measurement, a region where F_2 becomes nearly proportional to Q^2.

Next-to-leading order QCD analyses of the ZEUS data on deep inelastic scattering together with fixed-target data have been perfomed, from which the gluon and the quark densities of the proton and the value of the strong coupling constant, alpha_s(M_Z), were extracted. The study includes a full treatment of the experimental systematic uncertainties including point-to-point correlations. The resulting uncertainties in the parton density functions are presented. A combined fit for alpha_s(M_Z) and the gluon and qurak densities yields a value of alpha_s(M_Z) in agreement with the world average. The parton density functions derived from ZEUS data alone indicate the importance of HERA data in determining sea quark and gluon distributions at low x. The limits of applicability of the theoretical formalism have been explored by comparing the fit predictions to ZEUS data at very low Q^2.

We have developed a novel and highly radiation-tolerant n-in-p silicon microstrip sensor for very high radiation environments such as in the Super Large Hadron Collider. The sensors are designed for a fluence of 1×1015 neq/cm2 and are fabricated from p-type, FZ, 6 in. (150 mm) wafers onto which we lay out a single 9.75 cm×9.75 cm large-area sensor and several 1 cm×1 cm miniature sensors with various n-strip isolation structures. By evaluating the sensors both pre- and post-irradiation by protons and neutrons, we find that the full depletion voltage evolves to approximately 800 V and that the n-strip isolation depends on the p+ concentration. In addition, we characterize the interstrip resistance, interstrip capacitance and the punch-through-protection (PTP) voltage. The first fabrication batch allowed us to identify the weak spots in the PTP and the stereo strip layouts. By understanding the source of the weakness, the mask was modified accordingly. After modification, the follow-up fabrication batches and the latest fabrication of about 30 main sensors and associated miniature sensors have shown good performance, with no sign of microdischarge up to 1000 V.

Inclusive production of $D^*(2010)$ mesons in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 81.9 pb$^{-1}$. The decay channel $D^{* +}\to D^0 \pi^+ $ with $D^0\to K^-\pi^+$ and corresponding antiparticle decay were used to identify $D^*$ mesons. Differential $D^*$ cross sections with $1.5<Q^2<1000$ GeV$^2$ and $0.02<y<0.7$ in the kinematic region $1.5<p_T(D^*)<15$ GeV and $|\eta(D^*)|<1.5$ are compared to different QCD calculations incorporating different parameterisations of the parton densities in the proton. The data show sensitivity to the gluon distribution in the proton and are reasonably well described by next-to-leading-order QCD with the ZEUS NLO QCD fit used as the input parton density in the proton. The observed cross section is extrapolated to the full kinematic region in $p_T(D^*)$ and $\eta(D^*)$ in order to determine the open-charm contribution, $F_2^{\rm charm}(x,Q^2)$, to the proton structure function, $F_2$. Since, at low $Q^2$, the uncertainties of the data are comparable to those from the QCD fit, the measured differential cross sections in $y$ and $Q^2$ should be used in future fits to constrain the gluon density.

Inclusive jet differential cross sections have been measured in neutral current deep inelastic e+p scattering for boson virtualities Q2>125 GeV2. The data were taken using the ZEUS detector at HERA and correspond to an integrated luminosity of 38.6 pb−1. Jets were identified in the Breit frame using the longitudinally invariant kT cluster algorithm. Measurements of differential inclusive jet cross sections are presented as functions of jet transverse energy (EBT,jet), jet pseudorapidity and Q2, for jets with EBT,jet>8 GeV. Next-to-leading-order QCD calculations agree well with the measurements both at high Q2 and high EBT,jet. The value of αs(MZ), determined from an analysis of dσ/dQ2 for Q2>500 GeV2, is αs(MZ)=0.1212±0.0017(stat.)+0.0023−0.0031(syst.)+0.0028−0.0027(th.).

The production of neutrons carrying at least 20% of the proton beam energy (xL>0.2) in e+p collisions has been studied with the ZEUS detector at HERA for a wide range of Q2, the photon virtuality, from photoproduction to deep inelastic scattering. The neutron-tagged cross section, ep→e′Xn, is measured relative to the inclusive cross section, ep→e′X, thereby reducing the systematic uncertainties. For xL> 0.3, the rate of neutrons in photoproduction is about half of that measured in hadroproduction, which constitutes a clear breaking of factorisation. There is about a 20% rise in the neutron rate between photoproduction and deep inelastic scattering, which may be attributed to absorptive rescattering in the γp system. For 0.64<xL<0.82, the rate of neutrons is almost independent of the Bjorken scaling variable x and Q2. However, at lower and higher xL values, there is a clear but weak dependence on these variables, thus demonstrating the breaking of limiting fragmentation. The neutron-tagged structure function, FLN(3)2(x,Q2,xL), rises at low values of x in a way similar to that of the inclusive F2(x,Q2) of the proton. The total γπ cross section and the structure function of the pion, Fπ2(xπ,Q2) where xπ=x/(1−xL), have been determined using a one-pion-exchange model, up to uncertainties in the normalisation due to the poorly understood pion flux. At fixed Q2, Fπ2 has approximately the same x dependence as F2 of the proton.

E896 has measured Lambda production in 11.6A GeV/c Au-Au collisions over virtually the whole rapidity phase space. The midrapidity p(t) distributions have been measured for the first time at this energy and appear to indicate that the Lambda hyperons have different freeze-out conditions than protons. A comparison with the relativistic quantum molecular dynamics model shows that while there is good shape agreement at high rapidity the model predicts significantly different slopes of the m(t) spectra at midrapidity. The data, where overlap occurs, are consistent with previously reported measurements.

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.

The upgrade of the HERA accelerator has provided much increased collider luminosity. In turn, the improvements have necessitated a new design for the ZEUS luminosity measurements. The intense synchrotron radiation field, as well as the high probability of a bremsstrahlung photon in each bunch crossing, posed new experimental constraints. In this report, we describe how these challenges were met with the ZEUS luminosity spectrometer system. The design, testing and commissioning of the device are described, and the results from the initial operational experience are reported.

The exclusive electroproduction of omega mesons, ep -> e omega p, has been studied in the kinematic range 3<Q^2<20 GeV^2, 40<W<120 GeV and |t|<0.6 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 37.7 pb^{-1}. The omega mesons were identified via the decay omega -> pi^+pi^-pi^0. The exclusive (ep -> e omega p) cross section in the above kinematic region is 0.108 +- 0.014(stat.) +- 0.026(syst.) nb. The reaction ep -> e phi p, phi -> pi^+pi^-pi^0, has also been measured. The cross sections, as well as the cross-section ratios omega/rho and omega/phi, are presented as a function of W and Q^2. Thus, for the first time, the properties of omega electroproduction can be compared to those of rho^0, phi and J/psi electroproduction at high W.

Cross sections for ${e}^{+}p$ neutral current deep inelastic scattering have been measured at a center-of-mass energy of $\sqrt{s}=318\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ with the ZEUS detector at HERA using an integrated luminosity of $63.2\text{ }{\mathrm{p}\mathrm{b}}^{\ensuremath{-}1}$. The double-differential cross section, ${d}^{2}\ensuremath{\sigma}/dxd{Q}^{2}$, is presented for $200\text{ }{\mathrm{G}\mathrm{e}\mathrm{V}}^{2}&lt;{Q}^{2}&lt;30\text{ }000\text{ }{\mathrm{G}\mathrm{e}\mathrm{V}}^{2}$ and for $0.005&lt;x&lt;0.65$. The single-differential cross sections $d\ensuremath{\sigma}/d{Q}^{2}$, $d\ensuremath{\sigma}/dx$ and $d\ensuremath{\sigma}/dy$ are presented for ${Q}^{2}&gt;200\text{ }{\mathrm{G}\mathrm{e}\mathrm{V}}^{2}$. The effect of $Z$-boson-exchange is seen in $d\ensuremath{\sigma}/dx$ measured for ${Q}^{2}&gt;10\text{ }000\text{ }{\mathrm{G}\mathrm{e}\mathrm{V}}^{2}$. The data presented here were combined with ZEUS ${e}^{+}p$ neutral current data taken at $\sqrt{s}=300\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ and the structure function ${F}_{2}^{\mathrm{e}\mathrm{m}}$ was extracted. All results agree well with the predictions of the Standard Model.

The photon-proton total cross section has been measured in the process e+ p -> e+ gamma p -> e+ X with the ZEUS detector at HERA. Events were collected with photon virtuality Q^2 < 0.02 GeV^2 and average gamma-p center-of-mass energy W_{gamma p} = 209 GeV in a dedicated run, designed to control systematic effects, with an integrated luminosity of 49 nb^{-1}. The measured total cross section is sigma_{tot}^{gamma p} = 174 +- 1 (stat.) +- 13 (syst.) microbarns. The energy dependence of the cross section is compatible with parameterizations of high-energy p-p and p-pbar data.

During summer and fall 2004, the response of a full slice of the ATLAS barrel detector to different particles was studied in controlled beam. One module of the ATLAS liquid argon barrel calorimeter—identical to the production modules and read out by the final front-end and back-end electronics—was used for electromagnetic calorimetry. This paper presents and discusses the electron performance of the LAr barrel calorimeter, including linearity, uniformity, and resolution with different amounts of material upstream the calorimeter and energies ranging from 1 to 250 GeV.

We are developing n+-in-p, p-bulk and n-readout, microstrip sensors, fabricated by Hamamatsu Photonics, as a non-inverting radiation hard silicon detector for the ATLAS tracker upgrade at the super-LHC (sLHC) proposed facility. The bulk radiation damage after neutron and proton irradiations is characterized with the leakage current, charge collection and full depletion voltage. The detectors should provide acceptable signal, signal-to-noise ratio exceeding 15, after the integrated luminosity of 6000 fb−1, which is twice the sLHC integrated luminosity goal.

The luminosity in the ZEUS detector was measured using photons from electron bremsstrahlung off protons. In 2001 the HERA collider was upgraded for operation at higher luminosity. At the same time the luminosity-measuring system of the ZEUS experiment was modified to tackle the expected higher photon rate and synchrotron radiation. The existing lead-scintillator calorimeter was equipped with radiation hard scintillator tiles and shielded against synchrotron radiation. In addition, a magnetic spectrometer was installed to measure the luminosity independently using photons converted in the beam-pipe exit window. The redundancy provided a reliable and robust luminosity determination with a systematic uncertainty of 1.7%. The experimental setup, the techniques used for luminosity determination and the estimate of the systematic uncertainty are reported.

The High Luminosity phase of the Large Hadron Collider will deliver 10 times more integrated luminosity than the existing collider, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry. As part of its upgrade program, the Compact Muon Solenoid collaboration is designing a high-granularity calorimeter (HGCAL) to replace the existing endcap calorimeters. It will feature unprecedented transverse and longitudinal readout and triggering segmentation for both electromagnetic and hadronic sections. The electromagnetic section and a large fraction of the hadronic section will be based on hexagonal silicon sensors of 0.5–1 cm2 cell size, with the remainder of the hadronic section being based on highly-segmented scintillators with silicon photomultiplier readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection. First hexagonal silicon modules, using the existing Skiroc2 front-end ASIC developed for CALICE, have been tested in beams at Fermilab and CERN in 2016. We present results from these tests, in terms of system stability, calibration with minimum-ionizing particles and resolution (energy, position and timing) for electrons, and the comparisons of these quantities with GEANT4-based simulation.

Large area linear Silicon Drift Detectors (SDD) are being developed for high energy and relativistic heavy ion collider experiments. SDDs have been proposed for the inner tracking detector in the STAR experiment at the BNL relativistic heavy ion collider to become operational in 1999. The Silicon Vertex Tracker (SVT) will consist of a three layer barrel structure composed of 216 individual detectors, each 6.3 × 6.3 cm2. Prototypes, including one-way drift detectors (4.5 × 4.5 cm2) and bi-directional drift detectors (6 × 6 cm2) have been manufactured,and their properties have been studied. Design considerations, as well as test results, are presented in this article. Recent work has focused on minimizing the inactive guard structure area in order to optimize tracking efficiency. Particular attention is given to discussion of parameters that are sensitive to the reduced guard structure area, such as leakage current, maximum voltage and drift non-linearities.

Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb^{-1}. Diffractive events were identified by the presence of a large rapidity gap in the final state. Differential cross sections have been measured in the kinematic region 1.5 &lt; Q^2 &lt; 200 GeV^2, 0.02 &lt; y &lt; 0.7, x_{IP} &lt; 0.035, beta &lt; 0.8, p_T(D*+/-) &gt; 1.5 GeV and |η(D*+/-)| &lt; 1.5. The measured cross sections are compared to theoretical predictions. The results are presented in terms of the open-charm contribution to the diffractive proton structure function. The data demonstrate a strong sensitivity to the diffractive parton densities.

A search for narrow-width resonances that decay into electron+jet or neutrino+jet has been performed with the ZEUS detector at HERA operating at center-of-mass energies of 300 and 318 GeV. An integrated e+p luminosity of 114.8 pb-1 and e-p luminosity of 16.7 pb-1 were used. No evidence for any resonance was found. Limits were derived on the Yukawa coupling as a function of the mass of a hypothetical resonance that has arbitrary decay branching ratios into electron+quark or neutrino+quark. These limits also apply to squarks predicted by R-parity-violating supersymmetry. Limits for the production of leptoquarks described by the Buchmuller-Ruckl-Wyler model were also derived for masses up to 400 GeV. For Yukawa coupling of 0.1, leptoquark masses up to 290 GeV are excluded.

We are developing n+-in-p, p-bulk and n-readout, microstrip sensors as a non-inverting radiation hard silicon detector for the ATLAS Tracker Upgrade at the super LHC experiment. The surface radiation damages of the sensors fabricated by Hamamatsu Photonics are characterized on the interstrip capacitance, interstrip resistance and punch-through protection evolution. The detector should provide acceptable strip isolation, exceeding the input impedance of the signal readout chip ∼1 kΩ, after the integrated luminosity of 6 ab−1, which is twice the luminosity goal.

A number of gravitation-motivated theories, as well as theories with new coloured fermions predict heavy particle towers with spectral densities $\rho(m^2)$ growing faster than $e^{m}$, a characteristic of nonlocalizable theories. It is shown that if a light scalar, like the Higgs boson, interacts strongly with a heavy scalar particle tower with exponentially rising degeneracy, then the local low-energy theory is equivalent to an effective nonlocal scalar QFT. For energies approaching the nonlocality scale $p^2\simeq\Lambda_{NL}^2$, the scalar propagator and scattering amplitudes are modified by nonlocal factors of the form $e^{p^2/\Lambda^2_{NL}}$. The double-Higgs production measurement at the LHC is proposed as a highly sensitive probe of nonlocality at the electroweak scale.

The subjet multiplicity has been measured in neutral current e+p interactions at Q2>125 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb−1. Jets were identified in the laboratory frame using the longitudinally invariant kT cluster algorithm. The number of jet-like substructures within jets, known as the subjet multiplicity, is defined as the number of clusters resolved in a jet by reapplying the jet algorithm at a smaller resolution scale ycut. Measurements of the mean subjet multiplicity, 〈nsbj〉, for jets with transverse energies ET,jet>15 GeV are presented. Next-to-leading-order perturbative QCD calculations describe the measurements well. The value of αs(MZ), determined from 〈nsbj〉 at ycut=10−2 for jets with 25<ET,jet<71 GeV, is αs(MZ)=0.1187±0.0017(stat.)+0.0024−0.0009(syst.)+0.0093−0.0076(th.).

The ATLAS collaboration R&D group “Development of n-in-p Silicon Sensors for very high radiation environment” has developed single-sided p-type 9.75 cm×9.75 cm sensors with an n-type readout strips having radiation tolerance against the 1015 1-MeV neutron equivalent (neq)/cm2 fluence expected in the Super Large Hadron Collider. The compiled results of an evaluation of the bulk and strip parameter characteristics of 19 new non-irradiated sensors manufactured by Hamamatsu Photonics are presented in this paper. It was verified in detail that the sensors comply with the technical specifications required before irradiation. The reverse bias voltage dependence of various parameters, frequency dependence of tested capacitances, and strip scans of more than 23,000 strips as a test of parameter uniformity and strip quality over the whole sensor area have been carried out at Stony Brook University, Cambridge University, University of Geneva, and Academy of Sciences of CR and Charles University in Prague. No openings, shorts, or pinholes were observed on all tested strips, confirming the high quality of sensors made by Hamamatsu Photonics.

The ATLAS experiment is preparing for the planned luminosity upgrade of the LHC (the super-luminous LHC or sLHC) with a programme of development for tracking able to withstand an order of greater magnitude radiation fluence and much greater hit occupancy rates than the current detector. This has led to the concept of an all-silicon tracker with an enhanced performance pixel-based inner region and short-strips for much of the higher radii. Both sub-systems employ many common technologies, including the proposed “stave” concept for integrated cooling and support. For the short-strip region, use of this integrated stave concept requires single-sided modules mounted on either side of a thin central lightweight support. Each sensor is divided into four rows of 23.82 mm length strips; within each row, there are 1280 strips of 74.5μm pitch. Well over a hundred prototype sensors are being delivered by Hamamatsu Photonics (HPK) to Japan, Europe and the US. We present results of the first 20 chip ABCN25 ASIC hybrids for these sensors, results of the first prototype 5120 strip module built with 40 ABCN25 read-out ASICs, and the status of the hybrids and modules being developed for the ATLAS tracker upgrade stave programme.

Searches in ep collisions for heavy excited fermions have been performed with the ZEUS detector at HERA. Excited states of electrons and quarks have been searched for in e+p collisions at a centre-of-mass energy of 300 GeV using an integrated luminosity of 47.7 pb−1. Excited electrons have been sought via the decays e∗→eγ, e∗→eZ and e∗→νW. Excited quarks have been sought via the decays q∗→qγ and q∗→qW. A search for excited neutrinos decaying via ν∗→νγ, ν∗→νZ and ν∗→eW is presented using e−p collisions at 318 GeV centre-of-mass energy, corresponding to an integrated luminosity of 16.7 pb−1. No evidence for any excited fermion is found, and limits on the characteristic couplings are derived for masses ≲250 GeV.

Differential cross sections for jet photoproduction in the reaction ep→e jet X have been measured with the ZEUS detector at HERA using 82.2 pb−1 of integrated luminosity. Inclusive jet cross sections are presented as a function of the jet transverse energy, ETjet, for jets with ETjet>17 GeV and pseudorapidity −1<ηjet<2.5, in the γp centre-of-mass-energy range 142<Wγp<293 GeV. Scaled jet invariant cross sections are presented as a function of the dimensionless variable xT≡2ETjet/Wγp for 〈Wγp〉=180 and 255 GeV. Next-to-leading-order QCD calculations give a good description of the measured differential cross sections in both magnitude and shape. The ratio of scaled jet invariant cross sections at the two 〈Wγp〉 values shows clear non-scaling behaviour. A value for the strong coupling constant of αs(MZ)=0.1224±0.0001(stat.)+0.0022−0.0019(exp.)+0.0054−0.0042(th.) has been extracted from a QCD analysis of the measured dσ/dETjet. The variation of αs with ETjet is in good agreement with the running of αs as predicted by QCD.

The SemiConductor Tracker (SCT) data acquisition (DAQ) system will calibrate, configure, and control the approximately six million front-end channels of the ATLAS silicon strip detector. It will provide a synchronized bunch-crossing clock to the front-end modules, communicate first-level triggers to the front-end chips, and transfer information about hit strips to the ATLAS high-level trigger system. The system has been used extensively for calibration and quality assurance during SCT barrel and endcap assembly and for performance confirmation tests after transport of the barrels and endcaps to CERN. Operating in data-taking mode, the DAQ has recorded nearly twenty million synchronously-triggered events during commissioning tests including almost a million cosmic ray triggered events. In this paper we describe the components of the data acquisition system, discuss its operation in calibration and data-taking modes and present some detector performance results from these tests

This Report summarises the results of the second year's activities of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. The first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) focuses on predictions (central values and errors) for total Higgs production cross sections and Higgs branching ratios in the Standard Model and its minimal supersymmetric extension, covering also related issues such as Monte Carlo generators, parton distribution functions, and pseudo-observables. This second Report represents the next natural step towards realistic predictions upon providing results on cross sections with benchmark cuts, differential distributions, details of specific decay channels, and further recent developments.

Dijet differential cross sections for the reaction e+p -> e+ + jet + jet + X in the photoproduction regime have been measured with the ZEUS detector at HERA using an integrated luminosity of 42.7 pb**{-1}. The cross sections are given for photon-proton centre-of-mass energies in the range 134< W <277 GeV. The differential cross sections as a function of the dijet mass, Mjj, and of the dijet angular variables have been measured for 47 < Mjj < 160 GeV and compared to next-to-leading-order QCD calculations. The dijet events in the region 75< Mjj < 100 GeV have been used to derive a 95% C.L. upper limit on the cross section for Z0 photoproduction of sigma(e+ p -> e+ Z0 X} < 5.9 pb. Upper limits on the photoproduction of new heavy resonances decaying into two jets are also presented for masses in the range between 60 GeV and 155 GeV.

We have measured the production of light nuclei (A<~3) in 11.6GeV/c Au-Au collisions at the Brookhaven Alternating Gradient Synchrotron (AGS). The transverse mass spectra are analyzed using a thermal fireball model, and the yields for different particle species are discussed assuming coalescence and fragmentation as possible production mechanisms. The wide acceptance range of the 3He measurements permits a broad study of the coalescence parameter B3 as functions of transverse momentum and rapidity. Comparisons with data obtained previously at AGS energies suggest that the simple models are insufficient to describe fully the production mechanisms of light nuclei.Received 24 August 2001DOI:https://doi.org/10.1103/PhysRevC.65.034907©2002 American Physical Society

Accelerating relativistic mirrors have long been recognized as viable settings where the physics mimic those of the black hole Hawking radiation. In 2017, Chen and Mourou proposed a novel method to realize such a system by traversing an ultra-intense laser through a plasma target with a decreasing density. An international AnaBHEL (Analog Black Hole Evaporation via Lasers) collaboration was formed with the objectives of observing the analog Hawking radiation, shedding light on the information loss paradox. To reach these goals, we plan to first verify the dynamics of the flying plasma mirror and characterize the correspondence between the plasma density gradient and the trajectory of the accelerating plasma mirror. We will then attempt to detect the analog Hawking radiation photons and measure the entanglement between the Hawking photons and their “partner particles”. In this paper, we describe our vision and strategy of AnaBHEL using the Apollon laser as a reference, and we report on the progress of our R&amp;D concerning the key components in this experiment, including the supersonic gas jet with a graded density profile, and the superconducting nanowire single-photon Hawking detector. In parallel to these hardware efforts, we performed computer simulations to estimate the potential backgrounds, and derived analytic expressions for modifications to the blackbody spectrum of the Hawking radiation for a perfectly reflecting point mirror, due to the semi-transparency and finite-size effects specific to flying plasma mirrors. Based on this more realistic radiation spectrum, we estimate the Hawking photon yield to guide the design of the AnaBHEL experiment, which appears to be achievable.

A multispectral superconducting nanowire single-photon detector (SNSPD) that is sensitive to different incident photon wavelength bands, is proposed. The SNSPD consists of a distributed Bragg reflector (DBR), a gold mirror, and two regions employing four NbN nanowire meander layers. Using the DBR, both as a filter and a reflector, creates two distinct detection bands. The first detection band has a peak absorptance of 0.792 at a wavelength of 1164 nm, while the second band has a total absorptance of &gt;0.70 in the wavelength range 1440 to 2000 nm. The design of the proposed SNSPD can be tuned to provide sensitivity to different wavelength bands. While conventional SNSPDs do not typically provide photon wavelength sensitivity, the band-selection design proposed in this work opens up its potential applications for future quantum communication technology.

Theoretical progress in Higgs boson production and background processes is discussed with particular emphasis on QCD corrections at and beyond next-to-leading order as well as next-to-leading order electroweak corrections. The residual theoretical uncertainties of the investigated processes are estimated in detail. Moreover, recent investigations of the MSSM Higgs sector and other extensions of the SM Higgs sector are presented. The potential of the LHC and a high-energy linear e+e- collider for the measurement of Higgs couplings is analyzed.

Energetic neutrons produced in ep collisions at HERA have been studied with the ZEUS detector in the photoproduction regime at a mean photon–proton center-of-mass energy of 220 GeV. The neutrons carry a large fraction 0.64<xL<0.925 of the incoming proton energy, and the four-momentum transfer squared at the proton–neutron vertex is small, |t|<0.425GeV2. The xL distribution of the neutrons is measured in bins of t. The (1−xL) distributions in the t bins studied satisfy a power law dN/dxL∝(1−xL)a(t), with the powers a(t) following a linear function of t: a(t)=0.88±0.09(stat.)−0.39+0.34(syst.)−(2.81±0.42(stat.)−0.62+1.13(syst.)GeV−2)t. This result is consistent with the expectations of pion-exchange models, in which the incoming proton fluctuates to a neutron–pion state, and the electron interacts with the pion.

The dependence of the photon structure on the photon virtuality, Q2, is studied by measuring the reaction e+p→e++jet+jet+X at photon-proton centre-of-mass energies 134<W<223 GeV. Events have been selected in the Q2 ranges ≈ 0 GeV2, 0.1–0.55 GeV2, and 1.5–4.5 GeV2, having two jets with transverse energy ETjet>5.5 GeV in the final state. The dijet cross section has been measured as a function of the fractional momentum of the photon participating in the hard process, xγOBS. The ratio of the dijet cross section with xγOBS<0.75 to that with xγOBS>0.75 decreases as Q2 increases. The data are compared with the predictions of NLO pQCD and leading-order Monte Carlo programs using various parton distribution functions of the photon. The measurements can be interpreted in terms of a resolved photon component that falls with Q2 but remains present at values of Q2 up to 4.5 GeV2. However, none of the models considered gives a good description of the data.

A study of the antineutrino-jet mass spectrum in e^+p -&gt; antineutrino+X events at center-of-mass energy 300 GeV has been performed with the ZEUS detector at HERA using an integrated luminosity of 47.7 pb^-1. The mass spectrum is in good agreement with that expected from Standard Model processes over the antineutrino -jet mass range studied. No significant excess attributable to the decay of a narrow resonance is observed. By using both e^+p -&gt; e^+ X and e^+p -&gt; antineutrino X data, mass-dependent limits are set on the s-channel production of scalar and vector resonant states. Couplings to first-generation quarks are considered and limits are presented as a function of the e^+q and antineutrino-q branching ratios. These limits are used to constrain the production of leptoquarks and R-parity violating squarks.

A method is proposed to directly probe the Higgs boson compositeness using the unique characteristics of a boosted Higgs boson produced in association with a weak gauge boson ( $$W^{\pm },Z$$ ). The discovery potential for the upcoming LHC running is presented, showing that compositeness scales up to 3 TeV can be probed at the LHC with an integrated luminosity of $$\mathcal {L}=3000$$ fb $$^{-1}$$ collected at $$\sqrt{s}=13$$ TeV.

Diffractive production of D∗±(2010) mesons in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 44.3pb−1. Diffractive charm production is identified by the presence of a large rapidity gap in the final state of events in which a D∗±(2010) meson is reconstructed in the decay channel D∗+→(D0→K−π+)π+s (+ charge conjugate). Differential cross sections when compared with theoretical predictions indicate the importance of gluons in such diffractive interactions.

E896 was designed to search for the predicted short-lived six-quark H0 di-baryon. The goal is to enhance the existing knowledge by extending the search into regions of shorter lifetimes (approximately half that of the lambda) and via exploring a new creation channel, that of the coalescence of two lambdas. Two main tracking chambers are used, a distributed drift chamber positioned to measure low-pt and high-rapidity neutral particle decay products and a silicon drift detector array which measures particle production at mid-rapidity. Both detectors are also investigating lambda polarization, over their respective coverages, for Au-Au collisions at 11.3 GeV/nucleon. The current status of the H0 di-baryon search and preliminary results of the strange particle production and polarization measurements will be presented.

Inclusive phi-meson production in neutral current deep inelastic e+p scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 45 pb^{-1}. The phi mesons were studied in the range 10<Q2<100 GeV2, where Q2 is the virtuality of the exchanged photon, and in restricted kinematic regions in the transverse momentum, p_T, pseudorapidity, eta, and the scaled momentum in the Breit frame, x_p. Monte Carlo models with the strangeness-suppression factor as determined by analyses of e+e- annihilation events overestimate the cross sections. A smaller value of the strangeness-suppression factor reduces the predicted cross sections, but fails to reproduce the shapes of the measured differential cross sections. High-momentum phi mesons in the current region of the Breit frame give the first direct evidence for the strange sea in the proton at low x.

A novel search for heavy vector resonances in the $H\rightarrow b\bar{b}$ and $Z\rightarrow b\bar{b}$ final states in association with a leptonically decaying $V$ ($Z$ or $W$) and $W$-only respectively, is proposed. It is argued that excesses with respect to the Standard Model prediction should be observed in all final states (0, 1 or 2 leptons), with the 1-lepton final state being the strongest. Since the relative strengths of these excesses depend on branching ratios and efficiencies, this is a clear signal for the presence of heavy resonances or their low mass tails. A general vector-triplet model is used to explore the discovery potential as a function of the resonance mass and width. Recent Higgs to $b\bar{b}$ observation data reported by the experiments ATLAS and CMS are used to test the model. Current limits are extended to resonance widths over mass as large as 9%.

Received 5 September 2006DOI:https://doi.org/10.1103/PhysRevD.74.059906©2006 American Physical Society

Characteristics of the hadronic final state of diffractive deep inelastic scattering events $e\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{eXp}$ were studied in the kinematic range $4&lt;{M}_{X}&lt;35\mathrm{GeV},$ $4&lt;{Q}^{2}&lt;150{\mathrm{GeV}}^{2},$ $70&lt;W&lt;250\mathrm{GeV},$ and $0.0003&lt;{x}_{P}&lt;0.03$ with the ZEUS detector at the DESY ep collider HERA using an integrated luminosity of 13.8 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$. The events were tagged by identifying the diffractively scattered proton using the leading proton spectrometer. The properties of the hadronic final state X were studied in its center-of-mass frame using thrust, thrust angle, sphericity, energy flow, transverse energy flow, and ``seagull'' distributions. As the invariant mass of the system increases, the final state becomes more collimated, more aligned, and more asymmetric in the average transverse momentum with respect to the direction of the virtual photon. Comparisons of the properties of the hadronic final state with predictions from various Monte Carlo model generators suggest that the final state is dominated by $q\overline{q}g$ states at the parton level.

The baryon-baryon continuum invariant mass spectrum generated from relativistic nucleus + nucleus collision data may reveal the existence of doubly-strange dibaryons not stable against strong decay if they lie within a few MeV of threshold. Furthermore, since the dominant component of these states is a superposition of two color-octet clusters which can be produced intermediately in a color-deconfined quark-gluon plasma (QGP), an enhanced production of dibaryon resonances could be a signal of QGP formation. A total of eight, doubly-strange dibaryon states are considered for experimental search using the STAR detector (Solenoidal Tracker at RHIC) at the new Relativistic Heavy Ion Collider (RHIC). These states may decay to Lambda-Lambda and/or proton-Cascade-minus, depending on the resonance energy. STAR's large acceptance, precision tracking and vertex reconstruction capabilities, and large data volume capacity, make it an ideal instrument to use for such a search. Detector performance and analysis sensitivity are studied as a function of resonance production rate and width for one particular dibaryon which can directly strong decay to proton-Cascade-minus but not Lambda-Lambda. Results indicate that such resonances may be discovered using STAR if the resonance production rates are comparable to coalescence model predictions for dibaryon bound states.

Presented here are first tests of a Gaseous Photomultiplier based on a cascade of Thick GEM structures intended for gamma-ray position reconstruction in liquid argon. The detector has a MgF2 window, transparent to VUV light, and a CsI photocathode deposited on the first THGEM . A gain of 8⋅ 105 per photoelectron and ∼ 100% photoelectron collection efficiency are measured at stable operation settings. The excellent position resolution capabilities of the detector (better than 100 μm) at 100 kHz readout rate, is demonstrated at room temperature. Structural integrity tests of the detector and seals are successfully performed at cryogenic temperatures by immersing the detector in liquid Nitrogen, laying a good foundation for future operation tests in noble liquids.

Abstract A 45 × 45 mm rectangular n-type Silicon Drift Detector was studied in magnetic fields ranging from 0 to 4.7 T and for drift fields from 200 to 380 V/cm. Transport properties of electrons in silicon (Hall mobility, drift mobility and magnetoresistance) were determined by pulsing the detector with a Nd:YAG laser at different drift lengths and measuring both the transverse deflections of the signal and the increases in drift time versus an applied magnetic field. The width of the signal in both the drift and anode direction increased with magnetic field. The magnetic field was aligned parallel and normal to the drift direction. The detector was found to operate well for conditions expected in future experiments at the RHIC collider and experiment E896 at Brookhaven National Laboratory.

A search has been made for lepton-flavor-violating interactions of the type e+→plX, where l denotes a μ or τ with high transverse momentum, at a center-of-mass energy √s of 300 GeV with an integrated luminosity of 47.7 pb−1 using the ZEUS detector at HERA. No evidence was found for lepton-flavor violation and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below √s, limits are set on λeq1 √βlq, where λeq1 is the coupling of the LQ to an electron and a first-generation quark q1 and βlq is the branching ratio of the LQ to l and a quark. For LQ masses exceeding √s, limits are set on the four-fermion contact-interaction term λeqα λlqβ/M2LQ for leptoquarks that couple to an electron and a quark qα and also to l and a quark qβ. Some of the limits are also applicable to lepton-flavor-violating processes mediated by squarks in R-parity-violating supersymmetric models. In some cases involving heavy quarks and especially for l=τ, the ZEUS limits are the most stringent published to date.Received 8 January 2002DOI:https://doi.org/10.1103/PhysRevD.65.092004©2002 American Physical Society

The increase of the instantaneous luminosity at the High-Luminosity LHC (HL-LHC, phase 2) places stringent requirements on the detectors.New proposed calorimeters have to be designed to operate in the harsh radiation environment at the HL-LHC, where the average number of interactions per bunch crossing is expected to exceed 140.The LHC experiments have proposed various high-granularity calorimetric solutions.In this talk, I focus on the new CMS high-granularity calorimeter (HGCAL), a highly granular sampling calorimeter with approximately six million silicon sensor channels ( 0.5 cm 2 and 1.1 cm 2 cells) and about four hundred thousand scintillator tiles read out by on-tile silicon photomultipliers.The HGCAL electronics, besides measuring energy and position of the energy deposits, are also designed to measure the time of particle arrival with a precision of about 50 ps.In HGCAL, we have developed a reconstruction approach that fully exploits the granularity to achieve optimal electron, photon and hadron identification, as well as good energy resolution in the presence of pileup.

A multispectral superconducting nanowire single photon detector sensitive to different incident photon wavelength bands, is proposed. The SNSPD consists of a Distributed Bragg Reflector, a gold mirror, and two regions employing four NbN nanowires. Using the DBR both as a filter and a reflector, two distinct detection bands are created. The first detection band has a peak absorbance of &amp;gt; 0.75 at a wavelength of 1143 nm, while the second band has an absorbance of &amp;gt; 0.70 in the wavelength range 1440 to 2000 nm. The design of the device can be tuned to provide sensitivity in different wavelength bands. While SNSPDs do not typically provide photon wavelength sensitivity, the band-selection design proposed in this work opens up potential applications for future quantum communication technology.

A silicon-based fine granularity calorimeter is a potential technology for the future International Linear Collider ILC, the future circular collider CEPC, and is also the chosen technology for the upgraded CMS experiment of the Large Hadron Collider. Active silicon sensing pads are used as MIP counters and the standard calibration of the calorimeter uses weights based on the average energy loss, dEdx. In this work, the limitations of the dEdx calibration method in terms of energy linearity, scale and resolution are explored. In the case of a calorimeter with varying passive layer thickness as the one planned for CMS, the dEdx method leads to a significant constant term in the resolution function and a non-linearity of energy response. For these reasons, a method based on the calorimeter sampling fraction that exploits the per-event measured shower depth is presented and shown to deliver superior absolute energy scale, linearity and resolution. Calorimetric designs in which the back of the shower is sampled less, offer reduced cost without loss in performance. Therefore, a proper calibration as proposed here is crucial in obtaining the most cost- and performance-effective silicon-sampling calorimeter design.

A 45/spl times/45 mm rectangular n-type silicon drift detector was studied in magnetic fields ranging from 0 to 4.7 T and for drift fields from 200 to 380 V/cm. Transport properties of electrons in silicon (Hall mobility, drift mobility and magnetoresistance) were determined by pulsing the detector with a Nd:YAG laser at different drift lengths and measuring both the transverse deflections of the signal and the increases in drift time versus applied magnetic field. The width of the signal in both the drift and anode direction increased with magnetic field. The magnetic field was aligned parallel and normal to the the drift direction. The detector was found to operate well for conditions expected in future experiments at the RHIC collider and experiment E896 at Brookhaven National Laboratory.

A data-driven method for simultaneously extracting a potential Higgs to ZZ to 4e, 4mu, 2e2mu signal and its dominant backgrounds, is presented. The method relies on a combined fit of the 2-lepton, Z*, and 4-lepton invariant masses. The fit is assisted by normalization of the Z+X backgrounds in data control regions. The Higgs discovery potential for the next few years of LHC running is presented. The demonstrated high sensitivity of the method makes it ideal for the search performed by the ATLAS and CMS experiments.

Using the QCD sum-rule approach, we show that the flavor-nonsinglet $H$ dibaryon states with ${J}^{\ensuremath{\pi}}{=1}^{+}, {J}^{\ensuremath{\pi}}{=0}^{+}, I=1$ (27 plet) are nearly degenerate with the ${J}^{\ensuremath{\pi}}{=0}^{+}, I=0$ singlet ${H}_{0}$ dibaryon, which has been predicted to be stable against strong decay, but has not been observed. Our calculation, which does not require an instanton correction, suggests that the ${H}_{0}$ is slightly heavier than these flavor-nonsinglet $H$'s over a wide range of the parameter space. If the singlet ${H}_{0}$ mass lies above the $\ensuremath{\Lambda}\ensuremath{\Lambda}$ threshold (2231 MeV), then the strong interaction breakup to $\ensuremath{\Lambda}\ensuremath{\Lambda}$ would produce a very broad resonance in the $\ensuremath{\Lambda}\ensuremath{\Lambda}$ invariant mass spectrum which would be very difficult to observe. On the other hand, if these flavor-nonsinglet $J=0$ and 1 $H$ dibaryons are also above the $\ensuremath{\Lambda}\ensuremath{\Lambda}$ threshold, but below the ${\ensuremath{\Xi}}^{0}n$ breakup threshold (2254 MeV), then because the direct, strong interaction decay to the $\ensuremath{\Lambda}\ensuremath{\Lambda}$ channel is forbidden, these flavor-nonsinglet states might be more amenable to experimental observation. The present results allow a possible reconciliation between the reported observation of $\ensuremath{\Lambda}\ensuremath{\Lambda}$ hypernuclei, which argue against a stable ${H}_{0}$, and the possible existence of $H$ dibaryons in general.

During the combined test-beam in summer 2004 a slice of the ATLAS barrel detector - including all detector sub systems from the inner tracker and the calorimetry, to the muon system - was exposed to particle beams (electrons, pions, photons, muons) with different energies (1 GeV to 350 GeV). The aim was to study the combined performance of the different detector sub systems in ATLAS-like conditions. We present performance results from the electromagnetic calorimetry, including uniformity, resolution, and linearity using two different calibration approaches.

The AGS Experiment 896 was designed to study strangeness production in Au—Au collisions at 11.6A GeV/c, in particular the formation of a six-quark di-baryon the H0. Heavy ion collisions provide favorable conditions for the H0 formation either via coalescence of two Λ particles (owing to the large Λ production cross section) or direct production from the possible formation of a quark-gluon plasma. E896 also measured strange meson and baryon distributions from mid-rapidity. Preliminary results from this experiment are presented as well as details of the expected sensitivity for the H0 search.

Non-local extensions of the Standard Model with a non-locality scale $\Lambda_{NL}$ have the effect of smearing the pointlike vertices of the Standard Model. At energies significantly lower than $\Lambda_{NL}$ vertices appear pointlike, while beyond this scale all beta functions vanish and all couplings approach a fixed point leading to scale invariance. Non-local SM extensions are ghost free, with the non-locality scale serving as an effective cutoff to radiative corrections of the Higgs mass. We argue that the data expected to be collected at the LHC phase 2 will have a sensitivity to non-local effects originating from a non-locality scale of a few TeV. Using an infinite derivative prescription, we study modifications to heavy vector-boson cross sections that can lead to an enhanced production of boosted Higgs bosons in a region of the kinematic phase space where the SM background is very small.

We report on the potential for the discovery of a Standard Model Higgs boson with the vector boson fusion mechanism in the mass range $115

A technique for improving the momentum resolution for low momentum charged particles in few layer silicon based trackers is presented.The particle momenta are determined from the measured Landau dE/dx distribution and the Bethe-Bloch formula in the 1/β 2 region.It is shown that a factor of two improvement of the momentum determination is achieved as compared to standard track fitting methods.This improvement is important in large scale heavy ion experiments which cover the low transverse momentum spectra using stand-alone silicon tracking devices with a few planes like the ones used in STAR at RHIC and ALICE at LHC.

This report describes a multi plane drift chamber that was designed and constructed to function as a topological detector for the BNL AGS E896 rare particle experiment. The chamber was optimized for good spatial resolution, two track separation, and a high uniform efficiency while operating in a 1.6 T magnetic field and subjected to long term exposure from a 11.6 GeV/nucleon beam of 106 Au ions per second.

Accelerating relativistic mirror has long been recognized as a viable setting where the physics mimics that of black hole Hawking radiation. In 2017, Chen and Mourou proposed a novel method to realize such a system by traversing an ultra-intense laser through a plasma target with a decreasing density. An international AnaBHEL (Analog Black Hole Evaporation via Lasers) Collaboration has been formed with the objectives of observing the analog Hawking radiation and shedding light on the information loss paradox. To reach these goals, we plan to first verify the dynamics of the flying plasma mirror and to characterize the correspondence between the plasma density gradient and the trajectory of the accelerating plasma mirror. We will then attempt to detect the analog Hawking radiation photons and measure the entanglement between the Hawking photons and their "partner particles". In this paper, we describe our vision and strategy of AnaBHEL using the Apollon laser as a reference, and we report on the progress of our R&amp;D of the key components in this experiment, including the supersonic gas jet with a graded density profile, and the superconducting nanowire single-photon Hawking detector. In parallel to these hardware efforts, we performed computer simulations to estimate the potential backgrounds, and derive analytic expressions for modifications to the blackbody spectrum of Hawking radiation for a perfectly reflecting, point mirror, due to the semit-ransparency and finite-size effects specific to flying plasma mirrors. Based on this more realistic radiation spectrum, we estimate the Hawking photon yield to guide the design of the AnaBHEL experiment, which appears to be achievable.

The main purpose of experiment E896 is to study the production of strange hadrons, in particular the predicted six-quark di-baryon, the H0. The placement of the silicon drift detector array (SDDA) close to the target in a 6.2T magnetic field is optimized for the reconstruction of a short lived H0 as well as of strange baryons (Λ, Λ, Ξ−). Simulations show that with the present data sample a detailed study of the Λ and Ξ− yields and distributions may be performed and a clear Λ signal might be detected. Simulations as well as a preliminary analysis of the SDDA data will be presented.

The HERA luminosity upgrade is expected to provide statistically significant measurements of the proton structure functions at 0.5&gt;M_{Z}^2). The behaviour of the parton densities (PDFs) in this high x, Q2 regime is predicted from DGLAP evolution of PDF parametrizations from lower Q2 fits of the data. Uncertainties in the PDFs at high x may propagate to lower x through DGLAP evolution at very high Q2. In this presentation the behaviour of the PDFs at high x is reexamined with different parametrizations that have been tried earlier, and with somewhat different constraints, set primarily by existing fixed target data. We present and discuss the effects at Q2=40000GeV^2 and compare our results with uncertainties obtained from propagation of experimental errors at high x, high Q2 DIS data.

A 45x45 mm rectangular n-type Silicon Drift Detector was studied in magnetic fields ranging from 0 to 4.7 T and for drift fields from 200 to 380 V/cm. Transport properties of electrons in silicon (Hall mobility, drift mobilily and magnetoresistance) were determined by pulsing the detector with a Nd:Yag laser at different drift lengths and measuring both the transverse deflections of the signal and the increases in drift time versus an applied magnetic field. The width of the signal in both the drift and anode direction increased with magnetic field. The magnetic field was aligned parallel and normal to the the drift direction. The detector was found to operate well for conditions expected in future experiments at the RHIC collider and experiment E896 at Brookhaven National Laboratory.