Browsing by Author "Bergauer,T."

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Citation Count: 1
Combination of Measurements of the Top Quark Mass from Data Collected by the ATLAS and CMS Experiments at √=7 and 8 TeV
(American Physical Society, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Scodellaro,L.
A combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The datasets used correspond to an integrated luminosity of up to 5 and Formula Presented of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak Formula Presented channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is Formula Presented, with a total uncertainty of 0.33 GeV. © 2024 CERN, for the CMS and ATLASs Collaboration.
Citation Count: 0
Constraints on anomalous Higgs boson couplings from its production and decay using the WW channel in proton–proton collisions at s=13TeV
(Springer Nature, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Gomez,G.
A study of the anomalous couplings of the Higgs boson to vector bosons, including CP-violation effects, has been conducted using its production and decay in the WW channel. This analysis is performed on proton–proton collision data collected with the CMS detector at the CERN LHC during 2016–2018 at a center-of-mass energy of 13 TeV, and corresponds to an integrated luminosity of 138fb-1. The different-flavor dilepton (eμ) final state is analyzed, with dedicated categories targeting gluon fusion, electroweak vector boson fusion, and associated production with a W or Z boson. Kinematic information from associated jets is combined using matrix element techniques to increase the sensitivity to anomalous effects at the production vertex. A simultaneous measurement of four Higgs boson couplings to electroweak vector bosons is performed in the framework of a standard model effective field theory. All measurements are consistent with the expectations for the standard model Higgs boson and constraints are set on the fractional contribution of the anomalous couplings to the Higgs boson production cross section. © The Author(s) 2024.
Citation Count: 1
Measurement of Energy Correlators inside Jets and Determination of the Strong Coupling Formula Presented
(American Physical Society, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Sonnadara,D.U.J.
Energy correlators that describe energy-weighted distances between two or three particles in a hadronic jet are measured using an event sample of Formula Presented proton-proton collisions collected by the CMS experiment and corresponding to an integrated luminosity of Formula Presented. The measured distributions are consistent with the trends in the simulation that reveal two key features of the strong interaction: confinement and asymptotic freedom. By comparing the ratio of the measured three- and two-particle energy correlator distributions with theoretical calculations that resum collinear emissions at approximate next-to-next-to-leading-logarithmic accuracy matched to a next-to-leading-order calculation, the strong coupling is determined at the Formula Presented boson mass: Formula Presented, the most precise Formula Presented value obtained using jet substructure observables. © 2024 CERN, for the CMS Collaboration.
Citation Count: 0
Measurement of multijet azimuthal correlations and determination of the strong coupling in proton-proton collisions at s=13TeV
(Springer Nature, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Gomez,G.
A measurement is presented of a ratio observable that provides a measure of the azimuthal correlations among jets with large transverse momentum pT. This observable is measured in multijet events over the range of pT=360–3170GeV based on data collected by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 134fb-1. The results are compared with predictions from Monte Carlo parton-shower event generator simulations, as well as with fixed-order perturbative quantum chromodynamics (pQCD) predictions at next-to-leading-order (NLO) accuracy obtained with different parton distribution functions (PDFs) and corrected for nonperturbative and electroweak effects. Data and theory agree within uncertainties. From the comparison of the measured observable with the pQCD prediction obtained with the NNPDF3.1 NLO PDFs, the strong coupling at the Z boson mass scale is αS(mZ)=0.1177±0.0013(exp)-0.0073 +0.0116(theo)=0.1177-0.0074 +0.0117, where the total uncertainty is dominated by the scale dependence of the fixed-order predictions. A test of the running of αS in the TeV region shows no deviation from the expected NLO pQCD behaviour. © The Author(s) 2024.
Citation Count: 0
Observation of the Formula Presented decay and studies of the Formula Presented baryon in proton-proton collisions at Formula Presented
(American Physical Society, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Piedra Gomez,J.
The first observation of the decay Formula Presented and measurement of the branching ratio of Formula Presented to Formula Presented are presented. The Formula Presented and Formula Presented mesons are reconstructed using their dimuon decay modes. The results are based on proton-proton colliding beam data from the LHC collected by the CMS experiment at Formula Presented in 2016-2018, corresponding to an integrated luminosity of Formula Presented. The branching fraction ratio is measured to be Formula Presented, where the last uncertainty comes from the uncertainties in the branching fractions of the charmonium states. New measurements of the Formula Presented baryon mass and natural width are also presented, using the Formula Presented final state, where the Formula Presented baryon is reconstructed through the decays Formula Presented, Formula Presented, Formula Presented, and Formula Presented. Finally, the fraction of Formula Presented baryons produced from Formula Presented decays is determined. © 2024 CERN, for the CMS Collaboration.
Citation Count: 0
Portable Acceleration of CMS Computing Workflows with Coprocessors as a Service
(Springer Nature, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; García,C.L.
Computing demands for large scientific experiments, such as the CMS experiment at the CERN LHC, will increase dramatically in the next decades. To complement the future performance increases of software running on central processing units (CPUs), explorations of coprocessor usage in data processing hold great potential and interest. Coprocessors are a class of computer processors that supplement CPUs, often improving the execution of certain functions due to architectural design choices. We explore the approach of Services for Optimized Network Inference on Coprocessors (SONIC) and study the deployment of this as-a-service approach in large-scale data processing. In the studies, we take a data processing workflow of the CMS experiment and run the main workflow on CPUs, while offloading several machine learning (ML) inference tasks onto either remote or local coprocessors, specifically graphics processing units (GPUs). With experiments performed at Google Cloud, the Purdue Tier-2 computing center, and combinations of the two, we demonstrate the acceleration of these ML algorithms individually on coprocessors and the corresponding throughput improvement for the entire workflow. This approach can be easily generalized to different types of coprocessors and deployed on local CPUs without decreasing the throughput performance. We emphasize that the SONIC approach enables high coprocessor usage and enables the portability to run workflows on different types of coprocessors. © The Author(s) 2024.
Citation Count: 1
Search for a high-mass dimuon resonance produced in association with b quark jets at s = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2023) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Blanco Fernández,S.
A search for high-mass dimuon resonance production in association with one or more b quark jets is presented. The study uses proton-proton collision data collected with the CMS detector at the LHC corresponding to an integrated luminosity of 138 fb−1 at a center-of-mass energy of 13 TeV. Model-independent limits are derived on the number of signal events with exactly one or more than one b quark jet. Results are also interpreted in a lepton-flavor-universal model with Z′ boson couplings to a bb quark pair (gb), an sb quark pair (gbδbs), and any same-flavor charged lepton (gℓ) or neutrino pair (gν), with |gν| = |gℓ|. For a Z′ boson with a mass mZ′ = 350 GeV (2 TeV) and |δbs| < 0.25, the majority of the parameter space with 0.0057 < |gℓ| < 0.35 (0.25 < |gℓ| < 0.43) and 0.0079 < |gb| < 0.46 (0.34 < |gb| < 0.57) is excluded at 95% confidence level. Finally, constraints are set on a Z′ model with parameters consistent with low-energy b → sℓℓ measurements. In this scenario, most of the allowed parameter space is excluded for a Z′ boson with 350 < mZ′ < 500 GeV, while the constraints are less stringent for higher mZ′ hypotheses. This is the first dedicated search at the LHC for a high-mass dimuon resonance produced in association with multiple b quark jets, and the constraints obtained on models with this signature are the most stringent to date. © The Author(s) 2023.
Citation Count: 0
Search for Baryon Number Violation in Top Quark Production and Decay Using Proton-Proton Collisions at Formula Presented
(American Physical Society, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Sonnadara,D.U.J.
A search is presented for baryon number violating interactions in top quark production and decay. The analysis uses data from proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC with an integrated luminosity of Formula Presented. Candidate events are selected by requiring two oppositely charged leptons (electrons or muons) and exactly one jet identified as originating from a bottom quark. Multivariate discriminants are used to separate the signal from the background. No significant deviation from the standard model prediction is observed. Upper limits are placed on the strength of baryon number violating couplings. For the first time the production of single top quarks via baryon number violating interactions is studied. This allows the search to set the most stringent constraints to date on the branching fraction of the top quark decay to a lepton, an up-type quark (Formula Presented or Formula Presented), and a down-type quark (Formula Presented, Formula Presented, or Formula Presented). The results improve the previous bounds by 3 to 6 orders of magnitude based on the fermion flavor combination of the baryon number violating interactions. © 2024 CERN, for the CMS Collaboration.
Citation Count: 0
Search for dark QCD with emerging jets in proton-proton collisions at s = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Morcillo Perez,C.M.
A search for “emerging jets” produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed using data collected by the CMS experiment corresponding to an integrated luminosity of 138 fb−1. This search examines a hypothetical dark quantum chromodynamics (QCD) sector that couples to the standard model (SM) through a scalar mediator. The scalar mediator decays into an SM quark and a dark sector quark. As the dark sector quark showers and hadronizes, it produces long-lived dark mesons that subsequently decay into SM particles, resulting in a jet, known as an emerging jet, with multiple displaced vertices. This search looks for pair production of the scalar mediator at the LHC, which yields events with two SM jets and two emerging jets at leading order. The results are interpreted using two dark sector models with different flavor structures, and exclude mediator masses up to 1950 (1950) GeV for an unflavored (flavor-aligned) dark QCD model. The unflavored results surpass a previous search for emerging jets by setting the most stringent mediator mass exclusion limits to date, while the flavor-aligned results provide the first direct mediator mass exclusion limits to date. © The Author(s) 2024.
Citation Count: 0
Search for long-lived heavy neutral leptons decaying in the CMS muon detectors in proton-proton collisions at Formula Presented
(American Physical Society, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Scodellaro,L.
A search for heavy neutral leptons (HNLs) decaying in the CMS muon system is presented. A data sample is used corresponding to an integrated luminosity of Formula Presented of proton-proton collisions at Formula Presented, recorded at the CERN LHC in 2016-2018. Decay products of long-lived HNLs could interact with the shielding materials in the CMS muon system and create hadronic and electromagnetic showers detected in the muon chambers. This distinctive signature provides a unique handle to search for HNLs with masses below 4 GeV and proper decay lengths of the order of meters. The signature is sensitive to HNL couplings to all three generations of leptons. Candidate events are required to contain a prompt electron or muon originating from a vertex on the beam axis and a displaced shower in the muon chambers. No significant deviations from the standard model background expectation are observed. In the electron (muon) channel, the most stringent limits to date are set for HNLs in the mass range of 2.1-3.0 (1.9-3.3) GeV, reaching mixing matrix element squared values as low as Formula Presented. © 2024 CERN, for the CMS Collaboration.
Citation Count: 3
Search for long-lived heavy neutral leptons with lepton flavour conserving or violating decays to a jet and a charged lepton
(Springer Science and Business Media Deutschland GmbH, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Vizan Garcia,J.M.
A search for long-lived heavy neutral leptons (HNLs) is presented, which considers the hadronic final state and coupling scenarios involving all three lepton generations in the 2–20 GeV HNL mass range for the first time. Events comprising two leptons (electrons or muons) and jets are analyzed in a data sample of proton-proton collisions, recorded with the CMS experiment at the CERN LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb−1. A novel jet tagger, based on a deep neural network, has been developed to identify jets from an HNL decay using various features of the jet and its constituent particles. The network output can be used as a powerful discriminating tool to probe a broad range of HNL lifetimes and masses. Contributions from background processes are determined from data. No excess of events in data over the expected background is observed. Upper limits on the HNL production cross section are derived as functions of the HNL mass and the three coupling strengths VℓN to each lepton generation ℓ and presented as exclusion limits in the coupling-mass plane, as lower limits on the HNL lifetime, and on the HNL mass. In this search, the most stringent limit on the coupling strength is obtained for pure muon coupling scenarios; values of |VμN2| > 5 (4) × 10−7 are excluded for Dirac (Majorana) HNLs with a mass of 10 GeV at a confidence level of 95% that correspond to proper decay lengths of 17 (10) mm. © The Author(s) 2024.
Citation Count: 0
Search for long-lived particles decaying in the CMS muon detectors in proton-proton collisions at Formula Presented
(American Physical Society, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Lasaosa García,C.
A search for long-lived particles (LLPs) decaying in the CMS muon detectors is presented. A data sample of proton-proton collisions at Formula Presented corresponding to an integrated luminosity of Formula Presented, recorded at the LHC in 2016-2018, is used. The decays of LLPs are reconstructed as high multiplicity clusters of hits in the muon detectors. In the context of twin Higgs models, the search is sensitive to LLP masses from 0.4 to 55 GeV and a broad range of LLP decay modes, including decays to hadrons, Formula Presented leptons, electrons, or photons. No excess of events above the standard model background is observed. The most stringent limits to date from LHC data are set on the branching fraction of the Higgs boson decay to a pair of LLPs with masses below 10 GeV. This search also provides the best limits for various intervals of LLP proper decay length and mass. Finally, this search sets the first limits at the LHC on a dark quantum chromodynamic sector whose particles couple to the Higgs boson through gluon, Higgs boson, photon, vector, and dark-photon portals, and is sensitive to branching fractions of the Higgs boson to dark quarks as low as Formula Presented. © 2024 CERN, for the CMS Collaboration.
Citation Count: 0
Search for Narrow Trijet Resonances in Proton-Proton Collisions at Formula Presented
(American Physical Society, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Martinez Rivero,C.
The first search for singly produced narrow resonances decaying to three well-separated hadronic jets is presented. The search uses proton-proton collision data corresponding to an integrated luminosity of Formula Presented at Formula Presented, collected at the CERN LHC. No significant deviations from the background predictions are observed between 1.75 and 9.00 TeV. The results provide the first mass limits on a right-handed boson Formula Presented decaying to three gluons and on an excited quark decaying via a vector boson to three quarks, as well as updated limits on a Kaluza-Klein gluon decaying via a radion to three gluons. © 2024 CERN, for the CMS Collaboration.
Citation Count: 0
Search for new physics in high-mass diphoton events from proton-proton collisions at s = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Martin Viscasillas,E.
Results are presented from a search for new physics in high-mass diphoton events from proton-proton collisions at s = 13 TeV. The data set was collected in 2016–2018 with the CMS detector at the LHC and corresponds to an integrated luminosity of 138 fb−1. Events with a diphoton invariant mass greater than 500 GeV are considered. Two different techniques are used to predict the standard model backgrounds: parametric fits to the smoothly-falling background and a first-principles calculation of the standard model diphoton spectrum at next-to-next-to-leading order in perturbative quantum chromodynamics calculations. The first technique is sensitive to resonant excesses while the second technique can identify broad differences in the invariant mass shape. The data are used to constrain the production of heavy Higgs bosons, Randall-Sundrum gravitons, the large extra dimensions model of Arkani-Hamed, Dimopoulos, and Dvali (ADD), and the continuum clockwork mechanism. No statistically significant excess is observed. The present results are the strongest limits to date on ADD extra dimensions and RS gravitons with a coupling parameter greater than 0.1. © The Author(s) 2024.
Citation Count: 0
Search for ZZ and ZH production in the bb¯bb¯ final state using proton-proton collisions at s=13TeV
(Springer Nature, 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Gomez,G.
A search for ZZ and ZH production in the bb¯bb¯ final state is presented, where H is the standard model (SM) Higgs boson. The search uses an event sample of proton-proton collisions corresponding to an integrated luminosity of 133fb-1 collected at a center-of-mass energy of 13TeV with the CMS detector at the CERN LHC. The analysis introduces several novel techniques for deriving and validating a multi-dimensional background model based on control samples in data. A multiclass multivariate classifier customized for the bb¯bb¯ final state is developed to derive the background model and extract the signal. The data are found to be consistent, within uncertainties, with the SM predictions. The observed (expected) upper limits at 95% confidence level are found to be 3.8 (3.8) and 5.0 (2.9) times the SM prediction for the ZZ and ZH production cross sections, respectively. © The Author(s) 2024.
Citation Count: 0
Searches for violation of Lorentz invariance in top quark pair production using dilepton events in 13 TeV proton-proton collisions
(Elsevier B.V., 2024) Hayrapetyan,A.; Tumasyan,A.; Adam,W.; Andrejkovic,J.W.; Bergauer,T.; Chatterjee,S.; Jayananda,M.K.
A search for violation of Lorentz invariance in the production of top quark pairs (tt‾) is presented. The measured normalized differential tt‾ production cross section, as a function of the sidereal time, is examined for potential modulations induced by Lorentz-invariance breaking operators in an effective field theory extension of the standard model (SM). The cross section is measured from collision events collected by the CMS detector at a center-of-mass-energy of 13 TeV, corresponding to an integrated luminosity of 77.8 fb−1, and containing one electron and one muon. The results are found to be compatible with zero, in agreement with the SM, and are used to place upper limits at 68% confidence level on the magnitude of the Lorentz-violating couplings ranging from 1–8×10−3. This is the first precision test of the isotropy in special relativity with top quarks at the LHC, restricting further the bounds on such couplings by up to two orders of magnitude with respect to previous searches conducted at the Tevatron. © 2024 CERN for the benefit of the CMS Collaboration