Publications
1269 results found
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Measurement of the top quark mass using a profile likelihood approach with the lepton plus jets final states in proton-proton collisions at √<i>s</i>=13TeV, EUROPEAN PHYSICAL JOURNAL C, Vol: 83, ISSN: 1434-6044
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Observation of τ Lepton Pair Production in Ultraperipheral Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV., Phys Rev Lett, Vol: 131
We present an observation of photon-photon production of τ lepton pairs in ultraperipheral lead-lead collisions. The measurement is based on a data sample with an integrated luminosity of 404 μb^{-1} collected by the CMS experiment at a center-of-mass energy per nucleon pair of sqrt[s_{NN}]=5.02 TeV. The γγ→τ^{+}τ^{-} process is observed for τ^{+}τ^{-} events with a muon and three charged hadrons in the final state. The measured fiducial cross section is σ(γγ→τ^{+}τ^{-})=4.8±0.6(stat)±0.5(syst) μb, where the second (third) term corresponds to the statistical (systematic) uncertainty in σ(γγ→τ^{+}τ^{-}) in agreement with leading-order QED predictions. Using σ(γγ→τ^{+}τ^{-}), we estimate a model-dependent value of the anomalous magnetic moment of the τ lepton of a_{τ}=0.001_{-0.089}^{+0.055}.
Hayrapetyan A, Tumasyan A, Adam W, et al., 2023, Search for a high-mass dimuon resonance produced in association with b quark jets at √s=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Hayrapetyan A, Tumasyan A, Adam W, et al., 2023, Search for new physics in multijet events with at least one photon and large missing transverse momentum in proton-proton collisions at 13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Measurements of the azimuthal anisotropy of prompt and nonprompt charmonia in PbPb collisions at √sNN = 5.02 TeV, Journal of High Energy Physics, Vol: 2023
The second-order (v 2) and third-order (v 3) Fourier coefficients describing the azimuthal anisotropy of prompt and nonprompt (from b-hadron decays) J/ψ, as well as prompt ψ(2S) mesons are measured in lead-lead collisions at a center-of-mass energy per nucleon pair of sNN = 5.02 TeV. The analysis uses a data set corresponding to an integrated luminosity of 1.61 nb −1 recorded with the CMS detector. The J/ψ and ψ(2S) mesons are reconstructed using their dimuon decay channel. The v 2 and v 3 coefficients are extracted using the scalar product method and studied as functions of meson transverse momentum and collision centrality. The measured v 2 values for prompt J/ψ mesons are found to be larger than those for nonprompt J/ψ mesons. The prompt J/ψ v 2 values at high p T are found to be underpredicted by a model incorporating only parton energy loss effects in a quark-gluon plasma medium. Prompt and nonprompt J/ψ meson v 3 and prompt ψ(2S) v 2 and v 3 values are also reported for the first time, providing new information about heavy quark interactions in the hot and dense medium created in heavy ion collisions. [Figure not available: see fulltext.]
Hayrapetyan A, Tumasyan A, Adam W, et al., 2023, 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, Physical Review D, Vol: 108, ISSN: 2470-0010
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.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for supersymmetry in final states with a single electron or muon using angular correlations and heavy-object identification in proton-proton collisions at √<i>s</i>=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Measurement of the Dependence of the Hadron Production Fraction Ratios f_{s}/f_{u} and f_{d}/f_{u} on B Meson Kinematic Variables in Proton-Proton Collisions at sqrt[s]=13 TeV., Phys Rev Lett, Vol: 131
The dependence of the ratio between the B_{s}^{0} and B^{+} hadron production fractions, f_{s}/f_{u}, on the transverse momentum (p_{T}) and rapidity of the B mesons is studied using the decay channels B_{s}^{0}→J/ψϕ and B^{+}→J/ψK^{+}. The analysis uses a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 61.6 fb^{-1}. The f_{s}/f_{u} ratio is observed to depend on the B p_{T} and to be consistent with becoming asymptotically constant at large p_{T}. No rapidity dependence is observed. The ratio of the B^{0} to B^{+} meson production fractions, f_{d}/f_{u}, is also measured, for the first time in proton-proton collisions, using the B^{0}→J/ψK^{*0} decay channel. The result is found to be within 1 standard deviation of unity and independent of p_{T} and rapidity, as expected from isospin invariance.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for a vector-like quark T′<i>→</i> tH via the diphoton decay mode of the Higgs boson in proton-proton collisions at √<i>s</i>=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Evidence for four-top quark production in proton-proton collisions at s=13TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 844, ISSN: 0370-2693
The production of four top quarks (tt¯tt¯) 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 138fb−1. Events that have no leptons (all-hadronic), one lepton, or two opposite-sign leptons (where lepton refers only to prompt electrons or prompt muons) are considered. This is the first tt¯tt¯ measurement that includes the all-hadronic final state. The observed significance of the tt¯tt¯ signal in these final states of 3.9 standard deviations (1.5 expected) provides evidence for tt¯tt¯ production, with a measured cross section of 36−11+12fb. Combined with earlier CMS results in other final states, the 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.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for new heavy resonances decaying to WW, WZ, ZZ, WH, or ZH boson pairs in the all-jets final state in proton-proton collisions at s=13TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 844, ISSN: 0370-2693
A search for new heavy resonances decaying to WW, WZ, ZZ, WH, or ZH boson pairs in the all-jets final state is presented. The analysis is based on proton-proton collision data recorded by the CMS detector in 2016–2018 at a centre-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 138 fb−1. The search is sensitive to resonances with masses between 1.3 and 6TeV, decaying to bosons that are highly Lorentz-boosted such that each of the bosons forms a single large-radius jet. Machine learning techniques are employed to identify such jets. No significant excess over the estimated standard model background is observed. A maximum local significance of 3.6 standard deviations, corresponding to a global significance of 2.3 standard deviations, is observed at masses of 2.1 and 2.9 TeV. In a heavy vector triplet model, spin-1 Z′ and W′ resonances with masses below 4.8TeV are excluded at the 95% confidence level (CL). These limits are the most stringent to date. In a bulk graviton model, spin-2 gravitons and spin-0 radions with masses below 1.4 and 2.7TeV, respectively, are excluded at 95% CL. Production of heavy resonances through vector boson fusion is constrained with upper cross section limits at 95% CL as low as 0.1 fb.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for medium effects using jets from bottom quarks in PbPb collisions at s<inf>NN</inf>=5.02TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 844, ISSN: 0370-2693
The first study of the shapes of jets arising from bottom (b) quarks in heavy ion collisions is presented. Jet shapes are studied using charged hadron constituents as a function of their radial distance from the jet axis. Lead-lead (PbPb) collision data at a nucleon-nucleon center-of-mass energy of sNN=5.02TeV were recorded by the CMS detector at the LHC, with an integrated luminosity of 1.69nb−1. Compared to proton-proton collisions, a redistribution of the energy in b jets to larger distances from the jet axis is observed in PbPb collisions. This medium-induced redistribution is found to be substantially larger for b jets than for inclusive jets.
Tumasyan A, Adam W, Bergauer T, et al., 2023, Two-particle azimuthal correlations in γp interactions using pPb collisions at s<inf><inf>NN</inf></inf>=8.16TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 844, ISSN: 0370-2693
The first measurements of the Fourier coefficients (VnΔ) of the azimuthal distributions of charged hadrons emitted from photon-proton (γp) interactions are presented. The data are extracted from 68.8 nb−1 of ultra-peripheral proton-lead (pPb) collisions at sNN=8.16TeV using the CMS detector. The high energy lead ions produce a flux of photons that can interact with the oncoming proton. This γp system provides a set of unique initial conditions with multiplicity lower than in photon-lead collisions but comparable to recent electron-positron and electron-proton data. The VnΔ coefficients are presented in ranges of event multiplicity and transverse momentum (pT) and are compared to corresponding hadronic minimum bias pPb results. For a given multiplicity range, the mean pT of charged particles is smaller in γp than in pPb collisions. For both the γp and pPb samples, V1Δ is negative, V2Δ is positive, and V3Δ consistent with 0. For each multiplicity and pT range, V2Δ is larger for γp events. The γp data are consistent with model predictions that have no collective effects.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for new physics in the τ lepton plus missing transverse momentum final state in proton-proton collisions at √<i>s</i>=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for a charged Higgs boson decaying into a heavy neutral Higgs boson and a W boson in proton-proton collisions at √<i>s</i>=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Measurement of differential cross sections for the production of a Z boson in association with jets in proton-proton collisions at √<i>s</i>=13 TeV, PHYSICAL REVIEW D, Vol: 108, ISSN: 2470-0010
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for Exotic Higgs Boson Decays H → AA → 4γ with Events Containing Two Merged Diphotons in Proton-Proton Collisions at Vs=13 TeV, PHYSICAL REVIEW LETTERS, Vol: 131, ISSN: 0031-9007
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Reconstruction of decays to merged photons using end-to-end deep learning with domain continuation in the CMS detector, Physical Review D, Vol: 108, ISSN: 2470-0010
A novel technique based on machine learning is introduced to reconstruct the decays of highly Lorentz-boosted particles. Using an end-to-end deep learning strategy, the technique bypasses existing rule-based particle reconstruction methods typically used in high energy physics analyses. It uses minimally processed detector data as input and directly outputs particle properties of interest. The new technique is demonstrated for the reconstruction of the invariant mass of particles decaying in the CMS detector. The decay of a hypothetical scalar particle Formula Presented into two photons, Formula Presented, is chosen as a benchmark decay. Lorentz boosts Formula Presented are considered, ranging from regimes where both photons are resolved to those where the photons are closely merged as one object. A training method using domain continuation is introduced, enabling the invariant mass reconstruction of unresolved photon pairs in a novel way. The new technique is validated using Formula Presented decays in LHC collision data.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Proton reconstruction with the CMS-TOTEM Precision Proton Spectrometer, Journal of Instrumentation, Vol: 18
The Precision Proton Spectrometer (PPS) of the CMS and TOTEM experiments collected 107.7 fb-1 in proton-proton (pp) collisions at theLHCat 13 TeV(Run 2). This paper describes the key features of the PPS alignment and optics calibrations, the proton reconstruction procedure, as well as the detector efficiency and the performance of the PPS simulation. The reconstruction and simulation are validated using a sample of (semi)exclusive dilepton events. The performance of PPS has proven the feasibility of continuously operating a near-beam proton spectrometer at a high luminosity hadron collider.
Hayrapetyan A, Tumasyan A, Adam W, et al., 2023, Observation of the Rare Decay of the η Meson to Four Muons, PHYSICAL REVIEW LETTERS, Vol: 131, ISSN: 0031-9007
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Observation of Same-Sign WW Production from Double Parton Scattering in Proton-Proton Collisions at sqrt[s]=13 TeV., Phys Rev Lett, Vol: 131
The first observation of the production of W^{±}W^{±} 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 138 fb^{-1} 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 W bosons decaying leptonically is 80.7±11.2(stat) _{-8.6}^{+9.5}(syst)±12.1(model) fb, whereas the measured fiducial cross section is 6.28±0.81(stat)±0.69(syst)±0.37(model) fb. The observed significance of the signal is 6.2 standard deviations above the background-only hypothesis.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, 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, European Physical Journal C, Vol: 83, ISSN: 1434-6044
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 / γ + X , in proton-tagged events from proton–proton collisions at s=13TeV , 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 / γ + X are set.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, First measurement of the top quark pair production cross section in proton-proton collisions at √<i>s</i>=13.6 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for Higgs Boson Decay to a Charm Quark-Antiquark Pair in Proton-Proton Collisions at sqrt[s]=13 TeV., Phys Rev Lett, Vol: 131
A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H→cc[over ¯], produced in association with a leptonically decaying V (W or Z) boson is presented. The search is performed with proton-proton collisions at sqrt[s]=13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb^{-1}. Novel charm jet identification and analysis methods using machine learning techniques are employed. The analysis is validated by searching for Z→cc[over ¯] in VZ events, leading to its first observation at a hadron collider with a significance of 5.7 standard deviations. The observed (expected) upper limit on σ(VH)B(H→cc[over ¯]) is 0.94 (0.50_{-0.15}^{+0.22})pb at 95% confidence level (C.L.), corresponding to 14 (7.6_{-2.3}^{+3.4}) times the standard model prediction. For the Higgs-charm Yukawa coupling modifier, κ_{c}, the observed (expected) 95% C.L. interval is 1.1<|κ_{c}|<5.5 (|κ_{c}|<3.4), the most stringent constraint to date.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for a heavy composite Majorana neutrino in events with dilepton signatures from proton-proton collisions at √s=13 Tev, PHYSICS LETTERS B, Vol: 843, ISSN: 0370-2693
Hayrapetyan A, Tumasyan A, Adam W, et al., 2023, Measurements of inclusive and differential cross sections for the Higgs boson production and decay to four-leptons in proton-proton collisions at √s=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Tumasyan A, Adam W, Bergauer T, et al., 2023, Azimuthal Correlations within Exclusive Dijets with Large Momentum Transfer in Photon-Lead Collisions., Phys Rev Lett, Vol: 131
The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at sqrt[s_{NN}]=5.02 TeV, corresponding to an integrated luminosity of 0.38 nb^{-1}, collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet transverse momentum vectors is found to be positive, and rising, as the dijet transverse momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Measurement of the electroweak production of Formula Presented in association with two jets in proton-proton collisions at Formula Presented, Physical Review D, Vol: 108, ISSN: 2470-0010
A 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.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Search for new physics using effective field theory in 13 TeV pp collision events that contain a top quark pair and a boosted Z or Higgs boson, Physical Review D, Vol: 108, ISSN: 2470-0010
A data sample containing top quark pairs ( t t ¯ ) produced in association with a Lorentz-boosted Z or Higgs boson is used to search for signs of new physics using effective field theory. The data correspond to an integrated luminosity of 138 fb - 1 of proton-proton collisions produced at a center-of-mass energy of 13 TeV at the LHC and collected by the CMS experiment. Selected events contain a single lepton and hadronic jets, including two identified with the decay of bottom quarks, plus an additional large-radius jet with high transverse momentum identified as a Z or Higgs boson decaying to a bottom quark pair. Machine learning techniques are employed to discriminate between t t ¯ Z or t t ¯ H events and events from background processes, which are dominated by t t ¯ + jets production. No indications of new physics are observed. The signal strengths of boosted t t ¯ Z and t t ¯ H production are measured, and upper limits are placed on the t t ¯ Z and t t ¯ H differential cross sections as functions of the Z or Higgs boson transverse momentum. The effects of new physics are probed using a framework in which the standard model is considered to be the low-energy effective field theory of a higher energy scale theory. Eight possible dimension-six operators are added to the standard model Lagrangian, and their corresponding coefficients are constrained via fits to the data.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Constraints on anomalous Higgs boson couplings to vector bosons and fermions from the production of Higgs bosons using the ττ final state, Physical Review D, Vol: 108, ISSN: 2470-0010
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 τ 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 C P -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.
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