Florian Beaudette

The D0 experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to D0.

We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.

The CMS collaboration has developed a fast Monte Carlo simulation of the CMS detector with event production rates ∼100 times faster than the GEANT4-based simulation, with nonetheless comparable accuracy for most of the physics objects typically considered in the analyses. We discuss basic technical principles of the CMS Fast Simulation and their implementation in the different components of the detector: the silicon tracker, the electromagnetic calorimeter, the hadronic calorimeter, the muon system, the Level 1 and the High Level Trigger. A few comparisons of the Fast Simulation results both with the GEANT4-based Full Simulation and with the LHC data are shown.

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in $p\overline{p}$ collisions at a center-of-mass energy $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of $150\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$. Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

A search for pair production of doubly-charged Higgs bosons in the process p pbar to H++H-- to mu+mu+mu-mu- is performed with the D0 Run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive di-muon data collected at an energy of sqrt{s}=1.96 TeV, corresponding to an integrated luminosity of 113 pb-1. In the absence of a signal, 95 % confidence level mass limits of M(H++L)>118.4 GeV/c2 and M(H++R)>98.2 GeV/c2 are set for left-handed and right-handed doubly-charged Higgs bosons, respectively, assuming 100% branching into muon pairs.

The result of a search at the LHC for heavy stable charged particles produced in pp collisions at $ \sqrt {s} = 7\;{\text{TeV}} $ is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb−1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c 2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.

Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.

A measurement of the top-antitop production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the top-antitop signal from W+jets and QCD multijet background events. The measured cross section is 173 + 39 - 32 (stat. + syst.) pb, consistent with standard model expectations.

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

The results based on 1992-95 data (Run 1) from the CDF and DO experiments on the measurements of the W boson mass and width are presented, along with the combined results. We report a Tevatron collider average M_W = 80.456 +- 0.059 GeV. We also report the Tevatron collider average of the directly measured W boson width Gamma_W = 2.115 +- 0.105 GeV. We describe a new joint analysis of the direct W mass and width measurements. Assuming the validity of the standard model, we combine the directly measured W boson width with the width extracted from the ratio of W and Z boson leptonic partial cross sections. This combined result for the Tevatron is Gamma_W = 2.135 +- 0.050 GeV. Finally, we use the measurements of the direct total W width and the leptonic branching ratio to extract the leptonic partial width Gamma(W -> e nu) = 224 +- 13 MeV.

We examine properties of tt¯ candidate events in lepton + jets final states to establish the helicities of W bosons in t→W+b decays. Our analysis is based on a direct calculation of a probability density for each event to correspond to a tt¯ final state, as a function of the helicity of the W boson. Using the 125 events/pb of data collected by the DØ experiment at the Fermilab Tevatron pp¯ Collider at s=1.8TeV, we obtain a longitudinal helicity fraction F0=0.56±0.31, consistent with the prediction of F0=0.70 from the standard model.

We present the results of a search for the production of new particles decaying into two jets in $\overline{p}p$ collisions at $\sqrt{s}=1.8\mathrm{TeV},$ using the D\O{} 1992--1995 data set corresponding to ${109\mathrm{}\mathrm{pb}}^{\ensuremath{-}1}.$ We exclude at the 95% confidence level the production of excited quarks ${(q}^{*})$ with masses below 775 GeV/${c}^{2},$ the most restrictive limit to date. We also exclude standard-model-like ${W}^{\ensuremath{'}}$ ${(Z}^{\ensuremath{'}})$ bosons with masses between 300 and 800 GeV/${c}^{2}$ (400 and 640 GeV/${c}^{2}).$ A ${W}^{\ensuremath{'}}$ boson with mass $<786\mathrm{GeV}{/c}^{2}$ has been excluded by previous measurements, and our lower limit is therefore the most stringent to date.

We present a search for large extra dimensions (ED) in pp collisions at a center-of-mass energy of 1.8 TeV using data collected by the DØ detector at the Fermilab Tevatron in 1994-1996. Data corresponding to 78.8+/-3.9 pb(-1) are examined for events with large missing transverse energy, one high-p(T) jet, and no isolated muons. There is no excess observed beyond expectation from the standard model, and we place lower limits on the fundamental Planck scale of 1.0 and 0.6 TeV for 2 and 7 ED, respectively.

The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.

The amplitude of the signal collected from the PbWO4 crystals of the CMS electromagnetic calorimeter is reconstructed by a digital filtering technique. The amplitude reconstruction has been studied with test beam data recorded from a fully equipped barrel supermodule. Issues specific to data taken in the test beam are investigated, and the implementation of the method for CMS data taking is discussed.

Abstract The upgrade of the CMS experiment for the high luminosity operation of the LHC comprises the replacement of the current endcap calorimeter by a high granularity sampling calorimeter (HGCAL). The electromagnetic section of the HGCAL is based on silicon sensors interspersed between lead and copper (or copper tungsten) absorbers. The hadronic section uses layers of stainless steel as an absorbing medium and silicon sensors as an active medium in the regions of high radiation exposure, and scintillator tiles directly read out by silicon photomultipliers in the remaining regions. As part of the development of the detector and its readout electronic components, a section of a silicon-based HGCAL prototype detector along with a section of the CALICE AHCAL prototype was exposed to muons, electrons and charged pions in beam test experiments at the H2 beamline at the CERN SPS in October 2018. The AHCAL uses the same technology as foreseen for the HGCAL but with much finer longitudinal segmentation. The performance of the calorimeters in terms of energy response and resolution, longitudinal and transverse shower profiles is studied using negatively charged pions, and is compared to GEANT4 predictions. This is the first report summarizing results of hadronic showers measured by the HGCAL prototype using beam test data.

We have measured the W boson mass using the DØ detector and a data sample of 82 pb−1 from the Fermilab Tevatron collider. This measurement uses W→eν decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such “edge” electrons have not been used in any previous DØ analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous DØ W boson mass measurements, we obtain MW=80.483±0.084 GeV. The 8% improvement from the previous DØ measurement is primarily due to the improved determination of the response parameters for non-edge electrons using the sample of Z bosons with non-edge and edge electrons.Received 10 April 2002DOI:https://doi.org/10.1103/PhysRevD.66.012001©2002 American Physical Society

Results are presented on a measurement of the ttbar pair production cross section in ppbar collisions at sqrt{s} = 1.8 TeV from nine independent decay channels. The data were collected by the Dzero experiment during the 1992-1996 run of the Fermilab Tevatron Collider. A total of 80 candidate events are observed with an expected background of 38.8 +- 3.3 events. For a top quark mass of 172.1 GeV/c^2, the measured cross section is 5.69 +- 1.21 (stat) +- 1.04 (sys) pb.

Performance tests of some aspects of the CMS ECAL were carried out on modules of the "barrel" sub-system in 2002 and 2003. A brief test with high energy electron beams was made in late 2003 to validate prototypes of the new Very Front End electronics. The final versions of the monitoring and cooling systems, and of the high and low voltage regulation were used in these tests. The results are consistent with the performance targets including those for noise and overall energy resolution, required to fulfil the physics programme of CMS at the LHC.

Abstract The Compact Muon Solenoid collaboration is designing a new high-granularity endcap calorimeter, HGCAL, to be installed later this decade. As part of this development work, a prototype system was built, with an electromagnetic section consisting of 14 double-sided structures, providing 28 sampling layers. Each sampling layer has an hexagonal module, where a multipad large-area silicon sensor is glued between an electronics circuit board and a metal baseplate. The sensor pads of approximately 1.1 cm 2 are wire-bonded to the circuit board and are readout by custom integrated circuits. The prototype was extensively tested with beams at CERN's Super Proton Synchrotron in 2018. Based on the data collected with beams of positrons, with energies ranging from 20 to 300 GeV, measurements of the energy resolution and linearity, the position and angular resolutions, and the shower shapes are presented and compared to a detailed Geant4 simulation.

The central inclusive jet cross section has been measured using a successive-combination algorithm for reconstruction of jets. The measurement uses 87.3 pb−1 of data collected with the DØ detector at the Fermilab Tevatron pp Collider during 1994–1995. The cross section, reported as a function of transverse momentum (pT>60 GeV) in the central region of pseudorapidity (|η|<0.5), exhibits reasonable agreement with next-to-leading order QCD predictions, except at low pT where the agreement is marginal.

A search for narrow resonances that decay into tt pairs has been performed using 130 pb(-1) of data in the lepton + jets channel collected by the Dphi detector in pp collisions at square root of (s)=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 GeV/c2. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to tt for narrow resonances as a function of the resonance mass MX. These limits are used to exclude the existence of a leptophobic top-color particle with mass MX<560 GeV/c2, using a theoretical cross section for a width GammaX=0.012MX.

We describe a measurement of the mass of the top quark from the purely hadronic decay modes of tt¯ pairs using all-jet data produced in pp¯ collisions at s=1.8TeV at the Fermilab Tevatron Collider. The data, which correspond to an integrated luminosity of 110.2±5.8pb−1, were collected with the DØ detector from 1992 to 1996. We find a top quark mass of 178.5±13.7(stat)±7.7(syst)GeV/c2.

The Compact Muon Solenoid (CMS) experiment has implemented a sophisticated two-level online selection system that achieves a rejection factor of nearly 105. During Run II, the LHC will increase its centre-of-mass energy up to 13 TeV and progressively reach an instantaneous luminosity of 2 × 1034 cm−2 s−1. In order to guarantee a successful and ambitious physics programme under this intense environment, the CMS Trigger and Data acquisition (DAQ) system has been upgraded. A novel concept for the L1 calorimeter trigger is introduced: the Time Multiplexed Trigger (TMT) . In this design, nine main processors receive each all of the calorimeter data from an entire event provided by 18 preprocessors. This design is not different from that of the CMS DAQ and HLT systems. The advantage of the TMT architecture is that a global view and full granularity of the calorimeters can be exploited by sophisticated algorithms. The goal is to maintain the current thresholds for calorimeter objects and improve the performance for their selection. The performance of these algorithms will be demonstrated, both in terms of efficiency and rate reduction. The callenging aspects of the pile-up mitigation and firmware design will be presented.

Based on 85 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ data of $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{TeV}$ collected using the D\O{} detector at Fermilab during the 1994--1995 run of the Tevatron, we present a direct measurement of the total decay width of the W boson ${\ensuremath{\Gamma}}_{W}.$ The width is determined from the transverse mass spectrum in the $\stackrel{\ensuremath{\rightarrow}}{W}e+{\ensuremath{\nu}}_{e}$ decay channel and found to be ${\ensuremath{\Gamma}}_{W}{=2.23}_{\ensuremath{-}0.14}^{+0.15}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.10(\mathrm{syst})\mathrm{GeV},$ consistent with the expectation from the standard model.

Mg -1Mq -1 = 1.84 ± 0.15 (stat.)± 0.22 0.18 (sys.).This ratio is

Using the D0 detector, we have studied events produced in proton-antiproton collisions that contain large forward regions with very little energy deposition (``rapidity gaps'') and concurrent jet production at center-of-mass energies of root-s = 630 and 1800 Gev. The fractions of forward and central jet events associated with such rapidity gaps are measured and compared to predictions from Monte Carlo models. For hard diffractive candidate events, we use the calorimeter to extract the fractional momentum loss of the scattered protons.

We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb$^{-1}$ of data collected by the D0 experiment at the Fermilab Tevatron Collider in 2002--2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-lightest SUSY particle.

Using the exclusive decay B0s-->J/psi(mu+mu-)phi(K+K-), we report the most precise single measurement of the B0s lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B0s lifetime, tau(B0s)=1.444(+0.098)(-0.090)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B0 meson using the exclusive decay B0-->J/psi(mu+mu-)K*0(892)(K+pi-). We reconstruct 1370 signal candidates, obtaining tau(B0)=1.473(+0.052)(-0.050)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, tau(B0s)/tau(B0)=0.980(+0.076)(-0.071)(stat)+/-0.003(sys).

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.

Using the DØ detector, we have observed events produced in p̄p collisions that contain W or Z bosons in conjunction with very little energy deposition (“rapidity gaps”) in large forward regions of the detector. The fraction of W boson events with a rapidity gap (a signature for diffraction) is 0.89±0.190.17%, and the probability that the non-diffractive background fluctuated to yield the observed diffractive signal is 3×10−14, corresponding to a significance of 7.5 σ. The Z boson sample has a gap fraction of 1.44±0.610.52%, with a significance of 4.4 σ. The diffractive events have very similar properties to the more common non-diffractive component.

Results from the completed Phase 1 Upgrade of the Compact Muon Solenoid (CMS) Level-1 Calorimeter Trigger are presented. The upgrade was performed in two stages, with the first running in 2015 for proton and heavy ion collisions and the final stage for 2016 data taking. The Level-1 trigger has been fully commissioned and has been used by CMS to collect over 43 fb−1 of data since the start of the Run II of the Large Hadron Collider (LHC). The new trigger has been designed to improve the performance at high luminosity and large number of simultaneous inelastic collisions per crossing (pile-up). For this purpose it uses a novel design, the Time Multiplexed Trigger (TMT), which enables the data from an event to be processed by a single trigger processor at full granularity over several bunch crossings. The TMT design is a modular design based on the μTCA standard. The trigger processors are instrumented with Xilinx Virtex-7 690 FPGAs and 10 Gbps optical links. The TMT architecture is flexible and the number of trigger processors can be expanded according to the physics needs of CMS. Sophisticated and innovative algorithms are now the core of the first decision layer of the experiment. The system has been able to adapt to the outstanding performance of the LHC, which ran with an instantaneous luminosity well above design. The performance of the system for single physics objects are presented along with the optimizations foreseen to maintain the thresholds for the harsher conditions expected during the LHC Run II and Run III periods.

We present data on multiple production of jets with transverse energies near 20 GeV in pp collisions at √ s = 1.8 TeV.QCD calculations in the partonshower approximation of pythia and herwig and the next-to-leading order approximation of jetrad are compared to the data for one, two, three, and four jet inclusive production.Transverse energy spectra and multiple jet angular and summed transverse-energy distributions are adequately described by the shower approximation while next-to-leading order calculations describe the data poorly.

Using 85.2 +/- 3.6 pb^-1 of p-pbar collisions collected at sqrt(s)=1.8 TeV with the D0 detector at Fermilab's Tevatron Collider, we present the results of a search for direct pair production of scalar top quarks ~t, the supersymmetric partners of the top quark. We examined events containing two or more jets and missing transverse energy, the signature of light scalar top quark decays to charm quarks and neutralinos. After selections, we observe 27 events while expecting 31.1 +/- 6.4 events from known standard model processes. Comparing these results to next-to-leading-order production cross sections, we exclude a significant region of ~t and neutralino phase space. In particular, we exclude the ~t mass m_~t < 122 GeV/c^2 for a neutralino mass of 45 GeV/c^2.

We have searched for the signature of 3- and 4-body decays of pair-produced scalar top quarks (stop) in the inclusive final state containing an electron, a muon, and significant missing transverse energy using a sample of pp̄ events corresponding to 108.3 pb−1 of data collected with the DØ detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the neutralino (χ̃01) is the lightest supersymmetric particle and is stable. No evidence for a signal is found and we derive cross-section upper limits as a function of stop (t̃) and neutralino masses in different decay scenarios leading to the bℓνχ̃01 final state.

The observation of the associated production of the Higgs boson with two top quarks in proton-proton collisions is one of the highlights of the LHC Run 2. Driven by the theoretical description of the physics processes, the Matrix Element Method (MEM) consists in computing a probability that an event is compatible with the signal hypothesis (ttH) or with one of the background hypotheses. It is a powerful classifying tool requiring high dimensional integral computations. The deployment of our MEM production code on GPU’s platform will be described. What follows will focus on the adaptation of the main components of the computations in OpenCL kernels, namely the Magraph matrix element code generator, VEGAS, and LHAPDF. Finally, the gain obtained on GPU’s platforms compared with classical CPU’s platforms will be assessed.

We present the results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron. We observe no evidence for leptoquark production and set a limit on sigma(pp*-->LQLQ-->nunu+jets) as a function of the mass of the leptoquark (m(LQ)). Assuming the decay LQ-->nuq, we exclude scalar leptoquarks for m(LQ) < 98 GeV/c(2), and vector leptoquarks for m(LQ) < 200 GeV/c(2) and coupling which produces the minimum cross section, at a 95% confidence level.

Lot of efforts have been devoted by ATLAS and CMS teams to improve the quality of LHC events analysis with the Matrix Element Method (MEM). Up to now, very few implementations try to face up the huge computing resources required by this method. We propose here a highly parallel version, combining MPI and OpenCL, which makes the MEM exploitation reachable for the whole CMS datasets with a moderate cost. In the article, we describe the status of two software projects under development, one focused on physics and one focused on computing. We also showcase their preliminary performance obtained with classical multi-core processors, CUDA accelerators and MIC co-processors. This let us extrapolate that with the help of 6 high-end accelerators, we should be able to reprocess the whole LHC run 1 within 10 days, and that we have a satisfying metric for the upcoming run 2. The future work will consist in finalizing a single merged system including all the physics and all the parallelism infrastructure, thus optimizing implementation for best hardware platforms.

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

We report the first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders. The data for the two-muon and two-jets final states were collected by the DO experiment, and correspond to an integrated luminosity of 94 +/- 5 pb^{-1}. Assuming that R-parity is violated via the single coupling lambda^{prime}_{211}, the number of candidate events is in agreement with expectation from the standard model. Exclusion contours are given in the (m_0,m_{1/2}) and (m_{tilde{chi}},m_{tilde{nu}}) planes for lambda^{prime}_{211}=0.09, 0.08 and 0.07.

A particle flow event-reconstruction algorithm has been successfully deployed in the CMS experiment and is nowadays used by most of the analyses. It aims at identifying and reconstructing individually each particle arising from the LHC proton-proton collision, by combining the information from all the subdetectors. The resulting particle-flow event reconstruction leads to an improved performance for the reconstruction of jets and MET, and for the identification of electrons, muons, and taus. The algorithm and its performance will be described. The commissioning phase, during which it was demonstrated that the algorithm was performing as expected from the simulation up to a high level of precision, will be presented. Finally, a selection of recent improvements in the CMS analyses obtained thanks to the particle-flow algorithm will be discussed.

We present results of a search for R-parity-violating decay of the neutralino chi;01, taken as the lightest supersymmetric particle, to a muon and two jets. The decay proceeds through a lepton-number violating coupling lambda(')(2jk) (j=1,2; k=1,2,3), with R-parity conservation in all other production and decay processes. In the absence of candidate events from 77.5+/-3.9 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron in pp collisions at sqrt[s]=1.8 TeV, and with an expected background of 0.18+/-0.03+/-0.02 events, we set limits on squark and gluino masses within the framework of the minimal low-energy supergravity-supersymmetry model.

The Compact Muon Solenoid (CMS) employs a sophisticated two-level online triggering system that has a rejection factor of up to 105. Since the beginning of Run II of LHC, the conditions that CMS operates in have become increasingly challenging. The centre-of-mass energy is now 13 TeV and the instantaneous luminosity currently peaks at 1.5 ×1034 cm−2s−1. In order to keep low physics thresholds and to trigger efficiently in such conditions, the CMS trigger system has been upgraded. A new trigger architecture, the Time Multiplexed Trigger (TMT) has been introduced which allows the full granularity of the calorimeters to be exploited at the first level of the online trigger. The new trigger has also benefited immensely from technological improvements in hardware. Sophisticated algorithms, developed to fully exploit the advantages provided by the new hardware architecture, have been implemented. The new trigger system started taking physics data in 2016 following a commissioning period in 2015, and since then has performed extremely well. The hardware and firmware developments, electron and photon algorithms together with their performance in challenging 2016 conditions is presented.

We report on a measurement of the ratio of the differential cross sections for W and Z boson production as a function of transverse momentum in proton–antiproton collisions at s=1.8 TeV. This measurement uses data recorded by the DØ detector at the Fermilab Tevatron in 1994–1995. It represents the first investigation of a proposal that ratios between W and Z observables can be calculated reliably using perturbative QCD, even when the individual observables are not. Using the ratio of differential cross sections reduces both experimental and theoretical uncertainties, and can therefore provide smaller overall uncertainties in the measured mass and width of the W boson than current methods used at hadron colliders.

The aim of the CMS particle flow event-reconstruction algorithm is to identify and reconstruct individually each particle arising from the LHC proton-proton collision, by combining the information from all subdetectors.The resulting global event description leads to an improved performance for the reconstruction of jets and MET, and for the identification of electrons, muons, and taus.The 7 TeV jet data, as well as leptons from J/Psi and W are used to finalize the commissioning of the particle-flow algorithm.The efficient reconstruction and identification of photons, charged and neutral hadrons, muons and electrons made possible by the versatility of the CMS apparatus, are shown to perform as expected up to a high level of precision.Results on particlebased jets and missing transverse energy, as well as on muons and electrons obtained through the reconstruction of standard candles are shown.

As part of its HL-LHC upgrade program, the CMS collaboration is replacing its existing endcap calorimeters with a high-granularity calorimeter (CE). The new calorimeter is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic and hadronic compartments. Due to its compactness, intrinsic time resolution, and radiation hardness, silicon has been chosen as active material for the regions exposed to higher radiation levels. The silicon sensors are fabricated as 20 cm (8") wide hexagonal wafers and are segmented into several hundred pads which are read out individually. As part of the sensor qualification strategy, 8" sensor irradiation with neutrons has been conducted at the Rhode Island Nuclear Science Center (RINSC) and followed by their electrical characterisation in 2020-21. The completion of this important milestone in the CE's R&D program is documented in this paper and it provides detailed account of the associated infrastructure and procedures. The results on the electrical properties of the irradiated CE silicon sensors are presented.

The CMS Level-1 calorimeter trigger is being upgraded in two stages to maintain performance as the LHC increases pile-up and instantaneous luminosity in its second run. In the first stage, improved algorithms including event-by-event pile-up corrections are used. New algorithms for heavy ion running have also been developed. In the second stage, higher granularity inputs and a time-multiplexed approach allow for improved position and energy resolution. Data processing in both stages of the upgrade is performed with new, Xilinx Virtex-7 based AMC cards.

A particle flow event-reconstruction algorithm has been successfully deployed in the CMS experiment and is nowadays used by most of the analyses. It aims at identifying and reconstructing individually each particle arising from the LHC proton-proton collision, by combining the information from all the subdetectors. The resulting particle-flow event reconstruction leads to an improved performance for the reconstruction of jets and MET, and for the identification of electrons, muons, and taus. The algorithm and its performance will be described. The commissioning phase, during which it was demonstrated that the algorithm was performing as expected from the simulation up to a high level of precision, will be presented. Finally, a selection of recent improvements in the CMS analyses obtained thanks to the particle-flow algorithm will be discussed.

The aim of the CMS particle flow event-reconstruction algorithm is to identify and reconstruct individually each particle arising from the LHC proton-proton collision, by combining the information from all subdetectors. The resulting particle-flow event reconstruction leads to an improved performance for the reconstruction of jets and MET, and for the identification of electrons, muons, and taus. The 7 TeV jet data, as well as leptons from J/Psi, W and Z Boson are used to finalize the commissioning of the particle-flow algorithm. The efficient reconstruction and identification of photons, charged and neutral hadrons, muons and electrons made possible by the versatility of the CMS apparatus, are shown to perform as expected up to a high level of precision. Results on particle-based jets and missing transverse energy, as well as on muons and electrons obtained through the reconstruction of standard candles are shown.

We describe a search for evidence of minimal supergravity (MSUGRA) in 92.7pb−1 of data collected with the DØ detector at the Fermilab Tevatron p¯p collider at √s=1.8TeV. Events with a single electron, four or more jets, and large missing transverse energy were used in this search. The major backgrounds are from W+jets, misidentified multijet, t¯t, and WW production. We observe no excess above the expected number of background events in our data. A new limit in terms of MSUGRA model parameters is obtained.Received 3 May 2002DOI:https://doi.org/10.1103/PhysRevD.66.112001©2002 American Physical Society

A prospective analysis for the discovery of a light standard model Higgs boson in the CMS experiment at the large hadron collider is presented. The analysis focuses on the inclusive single production p + p → H + X and the Higgs boson decay channel H → WW ( * ) → e + νe - ν, for a Higgs boson mass M H in the range 120 < M H < 160 GeV/c 2 . A full simulation of the detector response is performed and detailed electron, jet and missing transverse energy reconstruction algorithms are used. Emphasis is put on a realistic treatment of background contamination and systematics. A Higgs boson of mass M H ≥ 134 GeV/c 2 would be observed with a significance above three standard deviations in the e + νe - ν channel alone for an integrated LHC luminosity above 30 fb -1 .

For the High Luminosity LHC, the CMS collaboration made the ambitious choice of a high granularity design to replace the existing endcap calorimeters. Thousands of particles coming from the multiple interactions create showers in the calorimeters, depositing energy simultaneously in adjacent cells. The data are similar to 3D gray-scale image that should be properly reconstructed. In this paper, we investigate how to localize and identify the thousands of showers in such events with a Deep Neural Network model. This problem is well-known in the “Vision” domain, it belongs to the challenging class: “Object Detection”. Our project shares a lot of similarities with the ones treated in Industry but faces several technological challenges like the 3D treatment. We present the Mask R-CNN model which has already proven its efficiency in Industry (for 2D images). We also present the first results and our plans to extend it to tackle 3D HGCAL data.

With a high instantaneous luminosity and the large top quark pair production cross section, the Large Hadron Collider (LHC) will be a "top factory" allowing the analysis of millions of top events. After a short description of the top quark pair production mechanism and the cross section measurement, the accuracy of the top mass measurement needed for a sound consistency check of the Standard Model is briefly discussed. Different top mass measurement methods are presented. The observability of the single top quark production is described. Finally the observation of the Higgs boson produced in association with a top quark pair is discussed.

A search for massive resonances decaying to a Z boson and a photon is performed in events with a hadronically decaying Z boson candidate, separately in light-quark and b quark decay modes, identified using jet substructure and advanced b tagging techniques. Results are based on samples of proton-proton collisions collected with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 inverse femtobarns, respectively. The results of the search are combined with those of a similar search in the leptonic decay modes of the Z boson, based on the same data sets. Spin-0 resonances with various widths and with masses in a range between 0.2 and 3.0 TeV are considered. No significant excess is observed either in the individual analyses or the combination. The results are presented in terms of upper limits on the production cross section of such resonances and constitute the most stringent limits to date for a wide range of masses.

The inelastic hadronic cross section in proton-lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of 12.6 +/- 0.4 inverse nanobarns, has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton-lead collisions with hadronic activity produced in the pseudorapidity ranges 3<abs(eta)<5 and/or -5<abs(eta)<-3, corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be sigma[inel,pPb]=2061 +/- 3 (stat) +/- 34 (syst) +/- 72 (lum) mb. Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of sigma[inel,pPb] is compatible with that expected from the proton-proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small.

In this note we summarize the progress made by the calorimeter simulation task force (CALOTF) over the past year. The CALOTF was established in February 2008 in order to understand and reconcile the discrepancies observed between the CMS calorimetry simulation and test beam data recorded during 2004 and 2006. The simulation has been significantly improved by using a newer version of GEANT4 and an improved physics list for the full CMS detector simulation. Simulation times have been reduced by introducing flexible parameterizations to describe showering in the calorimeter (using a GFLASH-like approach) which have been tuned to the test beam data.

A measurement of the ttbar production cross section at sqrt(s)=13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.3 inverse femtobarns, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be sigma(ttbar)= 835 +/- 3 (stat) +/- 23 (syst) +/- 23 (lum) pb, in agreement with the standard model prediction. Using the expected dependence of the cross section on the pole mass of the top quark (m[t]), the value of m[t] is found to be 172.7+2.4-2.7 GeV.

The HGCROC3 is the final version of the front-end ASIC designed to readout the 6 million channels of the future HGCAL detector. Along with cutting-edge specifications in terms of low noise, time measurement precision, and ability to contribute to the Level-1 trigger decision, one of the key requirements for the HGCROC3 is a high radiation tolerance.Several irradiation campaigns have been carried out on HGCROC3 prototypes, with particular emphasis on the Total Integrated Dose (TID) and the Single-Event Effect (SEE) tests. In the context of the TID campaign, results are presented in terms of power consumption, charge and time measurement performance, clocks, and serial links robustness. Although previous versions of the same ASIC architecture show encouraging results in terms of SEE hardness, in this final version of the chip a special care is taken to reach the radiation tolerance requirement for critical blocks such as the digital counters, the clocks and the serializers. The corresponding studies of SEE effects on these components are also reported in this contribution.

A prospective analysis for the discovery of a light standard model Higgs boson in the CMS experiment at the large hadron collider is presented. The analysis focuses on the inclusive single production p + p → H + X and the Higgs boson decay channel , for a Higgs boson mass MH in the range 120 < MH < 160GeV/c2. A full simulation of the detector response is performed and detailed electron, jet and missing transverse energy reconstruction algorithms are used. Emphasis is put on a realistic treatment of background contamination and systematics. A Higgs boson of mass MH 134GeV/c2 would be observed with a significance above three standard deviations in the channel alone for an integrated LHC luminosity above 30 fb−1.

The electromagnetic calorimeter of the CMS experiment at CERN is an homogeneous calorimeter made of about 80000 Lead Tungstate crystals, that will start to operate at the LHC at the end of 2007. From June to November 2006, ten barrel Supermodules (1700 crystals each) were exposed to beam at CERN SPS, both in standalone and in association with portions of the Hadron Calorimeter. We present the description of the system used to configure and readout the calorimeter during the campaign. The full set of final readout electronics boards was employed, together with the pre-series version of the data acquisition software. During the campaign, the hardware and software concepts for the final system were validated. The system allowed the intercalibration of the ten Supermodules and allowed to perform several important studies of the detector performances, such as energy resolution, response linearity and radiation-hardness.

The purpose and layout of the detector control system for the CMS electromagnetic calorimeter (ECAL) are presented. The latest results from system prototype tests in the 2002-2004 ECAL testbeam programme, the current status of the system development and plans for its production, installation and commissioning are briefly discussed.

to test the validity of the Standard Model. The main goal of this thesis is to verify one of the theoretical predictions of the Standard Model of particle physics, the top-antitop production cross section, at the Tevatron collider.