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Yazar "Andrejkovic, J. W." seçeneğine göre listele

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A new calibration method for charm jet identification validated with proton-proton collision events at √s=13 TeV
(Iop Publishing Ltd, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Del Valle, A. Escalante
Many measurements at the LHC require efficient identification of heavy-flavour jets, i.e. jets originating from bottom (b) or charm (c) quarks. An overview of the algorithms used to identify c jets is described and a novel method to calibrate them is presented. This new method adjusts the entire distributions of the outputs obtained when the algorithms are applied to jets of different flavours. It is based on an iterative approach exploiting three distinct control regions that are enriched with either b jets, c jets, or light-flavour and gluon jets. Results are presented in the form of correction factors evaluated using proton-proton collision data with an integrated luminosity of 41.5 fb(-1) at root s = 13 TeV, collected by the CMS experiment in 2017. The closure of the method is tested by applying the measured correction factors on simulated data sets and checking the agreement between the adjusted simulation and collision data. Furthermore, a validation is performed by testing the method on pseudodata, which emulate various mismodelling conditions. The calibrated results enable the use of the full distributions of heavy-flavour identification algorithm outputs, e.g. as inputs to machine-learning models. Thus, they are expected to increase the sensitivity of future physics analyses.
A portrait of the Higgs boson by the CMS experiment ten years after the discovery
(Nature Portfolio, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
The most up-to-date combination of results on the properties of the Higgs boson is reported, which indicate that its properties are consistent with the standard model predictions, within the precision achieved to date. In July 2012, the ATLAS and CMS collaborations at the CERN Large Hadron Collider announced the observation of a Higgs boson at a mass of around 125 gigaelectronvolts. Ten years later, and with the data corresponding to the production of a 30-times larger number of Higgs bosons, we have learnt much more about the properties of the Higgs boson. The CMS experiment has observed the Higgs boson in numerous fermionic and bosonic decay channels, established its spin-parity quantum numbers, determined its mass and measured its production cross-sections in various modes. Here the CMS Collaboration reports the most up-to-date combination of results on the properties of the Higgs boson, including the most stringent limit on the cross-section for the production of a pair of Higgs bosons, on the basis of data from proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts. Within the uncertainties, all these observations are compatible with the predictions of the standard model of elementary particle physics. Much evidence points to the fact that the standard model is a low-energy approximation of a more comprehensive theory. Several of the standard model issues originate in the sector of Higgs boson physics. An order of magnitude larger number of Higgs bosons, expected to be examined over the next 15 years, will help deepen our understanding of this crucial sector.
A portrait of the Higgs boson by the CMS experiment ten years after the discovery (July ,10.1038/s41586-022-04892-x, 2022)
(Nature Portfolio, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
[No abstract available]
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
(Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
Asearch for decays to invisible particles ofHiggs 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 root s = 13 TeV 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 root 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).
A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer
(Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp -> pp + Z/gamma + X, in proton-tagged events from proton-proton collisions at root s = 13 TeV, recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600-1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. Model-independent upper limits on the visible production cross section of pp -> pp + Z/gamma + X are set.
Addendum: Measurement and QCD analysis of double-differential inclusive jet cross sections in proton-proton collisions at √s=13 TeV
(Springer, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Del Valle, A. Escalante
The QCD analysis at NNLO is repeated by using the NNLO interpolation grids for the double-differential inclusive jet cross section [1], which were released after the journal publication of the original analysis. The NNLOJET calculation used to derive these grids is based on the leading-colour and leading-flavour-number approximation and does not include the most recent subleading colour contributions. However, these contributions were reported in ref. [2] to be very small in inclusive jet production, in particular for a jet size of R = 0.7. The grids also contain an estimate of the numerical integration uncertainty of around 1% or less. To account for point-to-point fluctuations, this uncertainty, after consultation with the authors of NNLOJET, has been increased by a factor of two; however, its impact in the fit is negligible. A comparison of the measurement with predictions using various PDFs is shown in figure 1. Although the PDF parametrisation remains identical, higher precision in PDF and QCD parameters is expected by using NNLO grids consistently in the QCD analysis. These new results supersede those obtained by using the k-factor technique.
Analysis of the CP structure of the Yukawa coupling between the Higgs boson and τ leptons in proton-proton collisions at √s=13 TeV
(Springer, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Del Valle, A. Escalante
The first measurement of the CP structure of the Yukawa coupling between the Higgs boson and tau leptons is presented. The measurement is based on data collected in proton-proton collisions at root s = 13 TeV by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb(-1). The analysis uses the angular correlation between the decay planes of tau leptons produced in Higgs boson decays. The effective mixing angle between CP-even and CP-odd tau Yukawa couplings is found to be -1 +/- 19 degrees, compared to an expected value of 0 +/- 21 degrees at the 68.3% confidence level. The data disfavour the pure CP-odd scenario at 3.0 standard deviations. The results are compatible with predictions for the standard model Higgs boson.
Azimuthal anisotropy of dijet events in PbPb collisions at √sNN=5.02 TeV
(Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
The path-length dependent parton energy loss within the dense partonic medium created in lead-lead collisions at a nucleon-nucleon center-of-mass energy of root s(NN) = 5.02TeV is studied by determining the azimuthal anisotropies for dijets with high transverse momentum. The data were collected by the CMS experiment in 2018 and correspond to an integrated luminosity of 1.69 nb(-1). For events containing back-to-back jets, correlations in relative azimuthal angle and pseudorapidity (eta) between jets and hadrons, and between two hadrons, are constructed. The anisotropies are expressed as the Fourier expansion coefficients v(n), n = 2-4 of these azimuthal distributions. The dijet v(n) values are extracted from long-range (1.5 < vertical bar Delta eta vertical bar < 2.5) components of these correlations, which suppresses the background contributions from jet fragmentation processes. Positive dijet v(2) values are observed which increase from central to more peripheral events, while the v(3) and v(4) values are consistent with zero within experimental uncertainties.
Azimuthal correlations in Z plus jets events in proton-proton collisions at √s=13TeV
(Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
The production of Z bosons associated with jets is measured in pp collisions at v s = 13 TeV 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 > 30 GeV 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 Delta phi between the Z boson and the leading jet, as well as the correlations between the two leading jets are measured in three regions of p(T)(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 wheremultiple 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.
CMS PYTHIA 8 colour reconnection tunes based on underlying-event data
(Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
New 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 root 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) over bar) 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) over bar events in the semileptonic channel at 13 TeV.
Combination of Measurements of the Top Quark Mass from Data Collected by the ATLAS and CMS Experiments at √s=7 and 8 TeV
(Amer Physical Soc, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.
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 20 fb(-1) 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 t 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 m(t) = 172.52 +/- 0.14(stat) +/- 0.30(stat) GeV, with a total uncertainty of 0.33 GeV.
Combined search for electroweak production of winos, binos, higgsinos, and sleptons in proton-proton collisions at √s=13 TeV
(Amer Physical Soc, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.
A combination of the results of several searches for the electroweak production of the supersymmetric partners of standard model bosons, and of charged leptons, is presented. All searches use proton-proton collision data at root s = 13 TeV recorded with the CMS detector at the LHC in 2016-2018. The analyzed data correspond to an integrated luminosity of up to 137 fb(-1). The results are interpreted in terms of simplified models of supersymmetry. Two new interpretations are added with this combination: a model spectrum with the bino as the lightest supersymmetric particle together with mass-degenerate Higgsinos decaying to the bino and a standard model boson, and the compressed-spectrum region of a previously studied model of slepton pair production. Improved analysis techniques are employed to optimize sensitivity for the compressed spectra in the wino and slepton pair production models. The results are consistent with expectations from the standard model. The combination provides a more comprehensive coverage of the model parameter space than the individual searches, extending the exclusion by up to 125 GeV, and also targets some of the intermediate gaps in the mass coverage.
Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at √s=13 TeV
(Springer, 2021) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Del Valle, A. Escalante
A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 137 fb(-1) collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on themodel, the combined result excludes a top squarkmass up to 1325 GeV for amassless neutralino, and a neutralinomass up to 700 GeV for a top squarkmass of 1150 GeV. Top squarks with masses from 145 to 295 GeV, for neutralino masses from 0 to 100 GeV, with a mass difference between the top squark and the neutralino in a window of 30 GeV around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 GeV.
Constraints on anomalous Higgs boson couplings from its production and decay using the WW channel in proton-proton collisions at √s=13 TeV
(Springer, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.
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 138 fb(-1). The different-flavor dilepton (e mu) 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.
Constraints on anomalous Higgs boson couplings to vector bosons and fermions from the production of Higgs bosons using the tt final state
(Amer Physical Soc, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
A study of anomalous couplings of the Higgs boson to vector bosons and fermions is presented. The data were recorded by the CMS experiment at a center-of-mass energy of pp collisions at the LHC of 13 TeV and correspond to an integrated luminosity of 138 fb-1. The study uses Higgs boson candidates produced mainly in gluon fusion or electroweak vector boson fusion at the LHC that subsequently decay to a pair of z leptons. Matrix-element and machine-learning techniques were employed in a search for anomalous interactions. The results are combined with those from the four-lepton and two-photon decay channels to yield the most stringent constraints on anomalous Higgs boson couplings to date. The pure CP-odd scenario of the Higgs boson coupling to gluons is excluded at 2.4 standard deviations. The results are consistent with the standard model predictions.
Constraints on anomalous Higgs boson couplings to vector bosons and fermions in its production and decay using the four-lepton final state
(Amer Physical Soc, 2021) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.
Studies of CP violation and anomalous couplings of the Higgs boson to vector bosons and fermions are presented. The data were acquired by the CMS experiment at the LHC and correspond to an integrated luminosity of 137 fb(-1) at a proton-proton collision energy of 13 TeV. The kinematic effects in the Higgs boson's four-lepton decay H -> 4l and its production in association with two jets, a vector boson, or top quarks are analyzed, using a full detector simulation and matrix element techniques to identify the production mechanisms and to increase sensitivity to the tensor structure of the Higgs boson interactions. A simultaneous measurement is performed of up to five Higgs boson couplings to electroweak vector bosons (HVV), two couplings to gluons (Hgg), and two couplings to top quarks (Htt). The CP measurement in the Htt interaction is combined with the recent measurement in the H -> gamma gamma channel. The results are presented in the framework of anomalous couplings and are also interpreted in the framework of effective field theory, including the first study of CP properties of the Htt and effective Hgg couplings from a simultaneous analysis of the gluon fusion and top-associated processes. The results are consistent with the standard model of particle physics.
Development of the CMS detector for the CERN LHC Run 3
(Iop Publishing Ltd, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Arnold, B.; Bergauer, H.; Bergauer, T.
Since the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger.
Evidence for four-top quark production in proton-proton collisions at √s=13 TeV
(Elsevier, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
The production of four top quarks (tt over bar tt over bar ) is studied with LHC proton-proton collision data samples collected by the CMS experiment at a center-of-mass energy of 13 TeV, and corresponding to integrated luminosities of up to 138 fb-1. Events that have no leptons (all-hadronic), one lepton, or two oppositesign leptons (where lepton refers only to prompt electrons or prompt muons) are considered. This is the first tt over bar tt over bar measurement that includes the all-hadronic final state. The observed significance of the tt over bar tt over bar signal in these final states of 3.9 standard deviations (1.5 expected) provides evidence for tt over bar tt over bar production, with a measured cross section of 36+12 signal significance is 4.0 standard deviations (3.2 expected). The combination returns an observed cross section of 17 +/- 4 (stat) +/- 3 (syst) fb, which is consistent with the standard model prediction. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.
Evidence for tWZ production in proton-proton collisions at √s=13 TeV in multilepton final states
(Elsevier, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.
The first evidence for the standard model production of a top quark in association with a W boson and a Z boson is reported. The measurement is performed in multilepton final states, where the Z boson is reconstructed via its decays to electron or muon pairs. At least one W boson, associated or from top quark decay, decays leptonically, too. The analysed data were recorded by the CMS experiment at the CERN LHC in 2016-2018 in proton-proton collisions at root s = 13 TeV, and correspond to an integrated luminosity of 138 fb(-1). The measured cross section is 354 +/- 54(stat) +/- 95(syst) fb, and corresponds to a statistical significance of 3.4 standard deviations.
Evidence for WW/WZ vector boson scattering in the decay channel lνqq produced in association with two jets in proton-proton collisions at √s=13TeV
(Elsevier, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Del Valle, A. Escalante
Evidence is reported for electroweak (EW) vector boson scattering in the decay channel l nu qq of two weak vector bosons WV(V = Wor Z), produced in association with two parton jets. The search uses a data set of proton-proton collisions at 13TeVcollected with the CMS detector during 2016-2018 with an integrated luminosity of 138fb(-1). Events are selected requiring one lepton (electron or muon), moderate missing transverse momentum, two jets with a large pseudorapidity separation and a large dijet invariant mass, and a signature consistent with the hadronic decay of a W/Zboson. The cross section is computed in a fiducial phase space defined at parton level requiring all parton transverse momenta p(T)> 10 GeVand at least one pair of outgoing partons with invariant mass mqq> 100 GeV. The measured and expected EW WVproduction cross sections are 1.90(-0.46)(+0.5)3 pb and 2.23(-0.11)(+0.08)(scale) +/- 0.05(PDF) pb, respectively, where PDF is the parton distribution function. The observed EW signal strength is mu EW= 0.85 +/- 0.12 (stat)(-0.17)(+0.19)(syst), corresponding to a signal significance of 4.4 standard deviations with 5.1 expected, and it is measured keeping the quantum chromodynamics (QCD) associated diboson production fixed to the standard model prediction. This is the first evidence of vector boson scattering in the l nu qq decay channel at LHC. The simultaneous measurement of the EW and QCD associated diboson production agrees with the standard model prediction. (C) 2022 The Author(s). Published by Elsevier B.V.

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