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Öğe Azimuthal correlations in Z +jets events in proton–proton collisions at ?s=13TeV(Institute for Ionics, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationThe production of Z bosons associated with jets is measured in pp collisions at s=13TeV with data recorded with the CMS experiment at the LHC corresponding to an integrated luminosity of 36.3 fb-1 . The multiplicity of jets with transverse momentum pT>30GeV is measured for different regions of the Z boson’s pT(Z) , from lower than 10 GeV to higher than 100 GeV . The azimuthal correlation ?? between the Z boson and the leading jet, as well as the correlations between the two leading jets are measured in three regions of pT(Z) . The measurements are compared with several predictions at leading and next-to-leading orders, interfaced with parton showers. Predictions based on transverse-momentum dependent parton distributions and corresponding parton showers give a good description of the measurement in the regions where multiple parton interactions and higher jet multiplicities are not important. The effects of multiple parton interactions are shown to be important to correctly describe the measured spectra in the low pT(Z) regions. © 2023, The Author(s).Öğe CMS pythia 8 colour reconnection tunes based on underlying-event data(Institute for Ionics, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationNew sets of parameter tunes for two of the colour reconnection models, quantum chromodynamics-inspired and gluon-move, implemented in the pythia 8 event generator, are obtained based on the default CMS pythia 8 underlying-event tune, CP5. Measurements sensitive to the underlying event performed by the CMS experiment at centre-of-mass energies s=7 and 13 TeV , and by the CDF experiment at 1.96 TeV are used to constrain the parameters of colour reconnection models and multiple-parton interactions simultaneously. The new colour reconnection tunes are compared with various measurements at 1.96, 7, 8, and 13 TeV including measurements of the underlying-event, strange-particle multiplicities, jet substructure observables, jet shapes, and colour flow in top quark pair (t t ¯) events. The new tunes are also used to estimate the uncertainty related to colour reconnection modelling in the top quark mass measurement using the decay products of t t ¯ events in the semileptonic channel at 13 TeV . © 2023, The Author(s).Öğe Evaluation of HPK n+-p planar pixel sensors for the CMS Phase-2 upgrade(Elsevier B.V., 2023) Adam W.; Bergauer T.; Damanakis K.; Dragicevic M.; Frühwirth R.; Steininger H.; Beaumont W.To cope with the challenging environment of the planned high luminosity upgrade of the Large Hadron Collider (HL-LHC), scheduled to start operation in 2029, CMS will replace its entire tracking system. The requirements for the tracker are largely determined by the long operation time of 10 years with an instantaneous peak luminosity of up to 7.5 × 1034cm?2s?1 in the ultimate performance scenario. Depending on the radial distance from the interaction point, the silicon sensors will receive a particle fluence corresponding to a non-ionising energy loss of up to ?eq= 3.5 × 1016cm?2. This paper focuses on planar pixel sensor design and qualification up to a fluence of ?eq = 1.4 × 1016cm?2. For the development of appropriate planar pixel sensors an R&D program was initiated, which includes n+-p sensors on 150mm (6”) wafers with an active thickness of 150µm with pixel sizes of 100×25 µm2 and 50×50 µm2 manufactured by Hamamatsu Photonics K.K. (HPK). Single chip modules with ROC4Sens and RD53A readout chips were made. Irradiation with protons and neutrons, as well was an extensive test beam campaign at DESY were carried out. This paper presents the investigation of various assemblies mainly with ROC4Sens readout chips. It demonstrates that multiple designs fulfil the requirements in terms of breakdown voltage, leakage current and efficiency. The single point resolution for 50×50 µm2 pixels is measured as 4.0µm for non-irradiated samples, and 6.3µm after irradiation to ?eq = 7.2 × 1015cm?2. © 2023 Elsevier B.V.Öğe Inclusive and differential cross section measurements of single top quark production in association with a Z boson in proton-proton collisions at √s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis K.; Sağır, SinanInclusive and differential cross sections of single top quark production in association with a Z boson are measured in proton-proton collisions at a center-of-mass energy of 13 TeV with a data sample corresponding to an integrated luminosity of 138 fb−1 recorded by the CMS experiment. Events are selected based on the presence of three leptons, electrons or muons, associated with leptonic Z boson and top quark decays. The measurement yields an inclusive cross section of 87.9−7.3+7.5(stat)−6.0+7.3(syst) fb for a dilepton invariant mass greater than 30 GeV, in agreement with standard model (SM) calculations and represents the most precise determination to date. The ratio between the cross sections for the top quark and the top antiquark production in association with a Z boson is measured as 2.37−0.42+0.56(stat)−0.13+0.27(syst). Differential measurements at parton and particle levels are performed for the first time. Several kinematic observables are considered to study the modeling of the process. Results are compared to theoretical predictions with different assumptions on the source of the initial-state b quark and found to be in agreement, within the uncertainties. Additionally, the spin asymmetry, which is sensitive to the top quark polarization, is determined from the differential distribution of the polarization angle at parton level to be 0.54 ± 0.16 (stat) ± 0.06 (syst), in agreement with SM predictions.Öğe Measurement of the electroweak production of Formula Presented in association with two jets in proton-proton collisions at Formula Presented(American Physical Society, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationA measurement is presented for the electroweak production of a Formula Presented boson, a photon (Formula Presented), and two jets (j) in proton-proton collisions. The leptonic decay of the Formula Presented boson is selected by requiring one identified electron or muon and large missing transverse momentum. The two jets are required to have large invariant dijet mass and large separation in pseudorapidity. The measurement is performed with the data collected by the CMS detector at a center-of-mass energy of Formula Presented, corresponding to an integrated luminosity of Formula Presented. The cross section for the electroweak Formula Presented production is Formula Presented, whereas the total cross section for Formula Presented production is Formula Presented. Differential cross sections are also measured with the distributions unfolded to the particle level. All results are in agreement with the standard model expectations. Constraints are placed on anomalous quartic gauge couplings (aQGCs) in terms of dimension-8 effective field theory operators. These are the most stringent limits to date on the aQGCs parameters Formula Presented and Formula Presented. © 2023 CERN, for the CMS Collaboration.Öğe Measurement of the top quark mass using a profile likelihood approach with the lepton + jets final states in proton–proton collisions at ?s=13TeV(Institute for Ionics, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationThe mass of the top quark is measured in 36.3 fb-1 of LHC proton–proton collision data collected with the CMS detector at s=13TeV . The measurement uses a sample of top quark pair candidate events containing one isolated electron or muon and at least four jets in the final state. For each event, the mass is reconstructed from a kinematic fit of the decay products to a top quark pair hypothesis. A profile likelihood method is applied using up to four observables per event to extract the top quark mass. The top quark mass is measured to be 171.77±0.37GeV . This approach significantly improves the precision over previous measurements. © 2023, The Author(s).Öğe Measurements of jet multiplicity and jet transverse momentum in multijet events in proton–proton collisions at ?s=13TeV(Institute for Ionics, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationMultijet events at large transverse momentum (pT) are measured at s=13TeV using data recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 36.3fb-1 . The multiplicity of jets with pT>50GeV that are produced in association with a high- pT dijet system is measured in various ranges of the pT of the jet with the highest transverse momentum and as a function of the azimuthal angle difference ??1 , 2 between the two highest pT jets in the dijet system. The differential production cross sections are measured as a function of the transverse momenta of the four highest pT jets. The measurements are compared with leading and next-to-leading order matrix element calculations supplemented with simulations of parton shower, hadronization, and multiparton interactions. In addition, the measurements are compared with next-to-leading order matrix element calculations combined with transverse-momentum dependent parton densities and transverse-momentum dependent parton shower. © 2023, The Author(s).Öğe Observation of Same-Sign WW Production from Double Parton Scattering in Proton-Proton Collisions at Formula Presented(American Physical Society, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationThe first observation of the production of Formula Presented bosons from double parton scattering processes using same-sign electron-muon and dimuon events in proton-proton collisions is reported. The data sample corresponds to an integrated luminosity of Formula Presented recorded at a center-of-mass energy of 13 TeV using the CMS detector at the CERN LHC. Multivariate discriminants are used to distinguish the signal process from the main backgrounds. A binned maximum likelihood fit is performed to extract the signal cross section. The measured cross section for production of same-sign Formula Presented bosons decaying leptonically is Formula Presented, whereas the measured fiducial cross section is Formula Presented. The observed significance of the signal is 6.2 standard deviations above the background-only hypothesis. © 2023 CERN, for the CMS Collaboration.Öğe Search for CP violation using (Formula presented.) events in the lepton+jets channel in pp collisions at ?s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationResults are presented on a search for CP violation in the production and decay of top quark-antiquark pairs in the lepton+jets channel. The search is based on data from proton-proton collisions at s = 13 TeV, collected with the CMS detector, corresponding to an integrated luminosity of 138 fb?1. Possible CP violation effects are evaluated by measuring asymmetries in observables constructed from linearly independent four-momentum vectors of the final-state particles. The dimensionless chromoelectric dipole moment of the top quark obtained from the observed asymmetries is measured to be 0.04 ± 0.10 (stat) ± 0.07(syst), and the asymmetries exhibit no evidence for CP-violating effects, consistent with expectations from the standard model. [Figure not available: see fulltext.]. © 2023, The Author(s).Öğe A search for decays of the Higgs boson to invisible particles in events with a top-antitop quark pair or a vector boson in proton-proton collisions at ?s=13TeV(Institute for Ionics, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationA search for decays to invisible particles of Higgs bosons produced in association with a top-antitop quark pair or a vector boson, which both decay to a fully hadronic final state, has been performed using proton-proton collision data collected at s=13TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb-1 . The 95% confidence level upper limit set on the branching fraction of the 125 GeV Higgs boson to invisible particles, B(H ? inv) , is 0.54 (0.39 expected), assuming standard model production cross sections. The results of this analysis are combined with previous B(H ? inv) searches carried out at s=7 , 8, and 13 TeV in complementary production modes. The combined upper limit at 95% confidence level on B(H ? inv) is 0.15 (0.08 expected). © 2023, CERN for the benefit of the CMS Collaboration.Öğe Search for heavy resonances and quantum black holes in e?, e?, and ?? final states in proton-proton collisions at ?s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationA search is reported for heavy resonances and quantum black holes decaying into e?, e?, and ?? final states in proton-proton collision data recorded by the CMS experiment at the CERN LHC during 2016–2018 at s = 13 TeV, corresponding to an integrated luminosity of 138 fb?1. The e?, e?, and ?? invariant mass spectra are reconstructed, and no evidence is found for physics beyond the standard model. Upper limits are set at 95% confidence level on the product of the cross section and branching fraction for lepton flavor violating signals. Three benchmark signals are studied: resonant ? sneutrino production in R parity violating supersymmetric models, heavy Z? gauge bosons with lepton flavor violating decays, and nonresonant quantum black hole production in models with extra spatial dimensions. Resonant ? sneutrinos are excluded for masses up to 4.2TeV in the e? channel, 3.7TeV in the e? channel, and 3.6TeV in the ?? channel. A Z? boson with lepton flavor violating couplings is excluded up to a mass of 5.0TeV in the e? channel, up to 4.3Te V in the e? channel, and up to 4.1TeV in the ?? channel. Quantum black holes in the benchmark model are excluded up to the threshold mass of 5.6TeV in the e? channel, 5.2TeV in the e? channel, and 5.0TeV in the ?? channel. In addition, model-independent limits are extracted to allow comparisons with other models for the same final states and similar event selection requirements. The results of these searches provide the most stringent limits available from collider experiments for heavy particles that undergo lepton flavor violating decays. [Figure not available: see fulltext.]. © 2023, The Author(s).Öğe Search for nonresonant Higgs boson pair production in final state with two bottom quarks and two tau leptons in proton-proton collisions at s=13 TeV(Elsevier B.V., 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationA search for the nonresonant production of Higgs boson pairs (HH ) via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two tau leptons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of s=13TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 138fb?1. Events in which at least one tau lepton decays hadronically are considered and multiple machine learning techniques are used to identify and extract the signal. The data are found to be consistent, within uncertainties, with the standard model (SM) predictions. Upper limits on the HH production cross section are set to constrain the parameter space for anomalous Higgs boson couplings. The observed (expected) upper limit at 95% confidence level corresponds to 3.3 (5.2) times the SM prediction for the inclusive HH cross section and to 124 (154) times the SM prediction for the vector boson fusion HH cross section. At 95% confidence level, the Higgs field self-coupling is constrained to be within ?1.7 and 8.7 times the SM expectation, and the coupling of two Higgs bosons to two vector bosons is constrained to be within ?0.4 and 2.6 times the SM expectation. © 2022 The Author(s)Öğe Search for nonresonant Higgs boson pair production in the four leptons plus twob jets final state in proton-proton collisions at ?s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationThe first search for nonresonant production of Higgs boson pairs (HH) with one H decaying into four leptons and the other into a pair of b quarks is presented, using proton-proton collisions recorded at a center-of-mass energy of s = 13 TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 138 fb?1. A 95% confidence level upper limit of 32.4 is set on the signal strength modifier ?, defined as the ratio of the observed HH production rate in the HH? ZZ?b b ¯ ? 4 ?b b ¯ decay channel to the standard model (SM) expectation. Possible modifications of the H trilinear coupling ? HHH with respect to the SM value are investigated. The coupling modifier ??, defined as ? HHH divided by its SM prediction, is constrained to be within the observed (expected) range ?8.8 (?9.8) < ?? < 13.4 (15.0) at 95% confidence level. [Figure not available: see fulltext.]. © 2023, The Author(s).Öğe Search for the lepton-flavor violating decay of the Higgs boson and additional Higgs bosons in the Formula Presented final state in proton-proton collisions at Formula Presented(American Physical Society, 2023) Hayrapetyan A.; Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.A search for the lepton-flavor violating decay of the Higgs boson and potential additional Higgs bosons with a mass in the range 110-160 GeV to an Formula Presented pair is presented. The search is performed with a proton-proton collision dataset at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of Formula Presented. No excess is observed for the Higgs boson. The observed (expected) upper limit on the Formula Presented branching fraction for it is determined to be Formula Presented at 95% confidence level, the most stringent limit set thus far from direct searches. The largest excess of events over the expected background in the full mass range of the search is observed at an Formula Presented invariant mass of approximately 146 GeV with a local (global) significance of 3.8 (2.8) standard deviations. © 2023 CERN, for the CMS Collaboration.Öğe Search for top squarks in the four-body decay mode with single lepton final states in proton-proton collisions at ?s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; CMS CollaborationA search for the pair production of the lightest supersymmetric partner of the top quark, the top squark (t ~1), is presented. The search targets the four-body decay of the t ~1 , which is preferred when the mass difference between the top squark and the lightest supersymmetric particle is smaller than the mass of the W boson. This decay mode consists of a bottom quark, two other fermions, and the lightest neutralino (?~10), which is assumed to be the lightest supersymmetric particle. The data correspond to an integrated luminosity of 138 fb?1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC. Events are selected using the presence of a high-momentum jet, an electron or muon with low transverse momentum, and a significant missing transverse momentum. The signal is selected based on a multivariate approach that is optimized for the difference between m(t ~1) and m(?~10). The contribution from leading background processes is estimated from data. No significant excess is observed above the expectation from standard model processes. The results of this search exclude top squarks at 95% confidence level for masses up to 480 and 700 GeV for m(t ~1) ? m(?~10) = 10 and 80 GeV, respectively. [Figure not available: see fulltext.]. © 2023, The Author(s).
