Publications
2113 results found
Tumasyan A, Adam W, Andrejkovic JW, et al., 2023, Observation of triple J/psi meson production in proton-proton collisions, NATURE PHYSICS, ISSN: 1745-2473
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for new particles in an extended Higgs sector with four b quarks in the final state at s=13TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol: 835, ISSN: 0370-2693
A search for a massive resonance X decaying to a pair of spin-0 bosons ϕ that themselves decay to pairs of bottom quarks, is presented. The analysis is restricted to the mass ranges mϕ from 25 to 100 GeV and mX from 1 to 3 TeV. For these mass ranges, the decay products of each ϕ boson are expected to merge into a single large-radius jet. Jet substructure and flavor identification techniques are used to identify these jets. The search is based on CERN LHC proton-proton collision data at s=13TeV, collected with the CMS detector in 2016–2018, corresponding to an integrated luminosity of 138fb−1. Model-specific limits, where the two new particles arise from an extended Higgs sector, are set on the product of the production cross section and branching fraction for X→ϕϕ→(bb‾)(bb‾) as a function of the resonances' masses, where both the X→ϕϕ and ϕ→bb‾ branching fractions are assumed to be 100%. These limits are the first of their kind on this process, ranging between 30 and 1 fb at 95% confidence level for the considered mass ranges.
Tumasyan A, Adam W, Ambrogi F, et al., 2022, Nuclear modification of Y states in pPb collisions at √sNN = 5.02 TeV, Physics Letters B, Vol: 835, ISSN: 0370-2693
Production cross sections of Υ(1S), Υ(2S), and Υ(3S) states decaying into μ+μ− in proton-lead (pPb) collisions are reported using data collected by the CMS experiment at √sNN = 5.02 TeV. A comparison is made with corresponding cross sections obtained with pp data measured at the same collision energy and scaled by the Pb nucleus mass number. The nuclear modification factor for Υ(1S) is found to be RpPb(Υ(1S)) = 0.806±0.024 (stat)±0.059 (syst). Similar results for the excited states indicate a sequentialsuppression pattern, such that RpPb(Υ(1S)) > RpPb(Υ(2S)) > RpPb(Υ(3S)). The suppression of all states is much less pronounced in pPb than in PbPb collisions, and independent of transverse momentum pΥT and center-of-mass rapidity yΥCM of the individual Υ state in the studied range pΥT < 30 GeV/c and |yΥCM| <1.93. Models that incorporate final-state effects of bottomonia in pPb collisions are in better agreement with the data than those which only assume initial-state modifications.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for new particles in an extended Higgs sector with four b quarks in the final state at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:msqrt><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msqrt><mml:mo linebreak="goodbreak" linebreakstyle="after">=</mml:mo><mml:mn>13</mml:mn><mml:mrow><mml:mspace width="0.20em" /><mml:mtext>TeV</mml:mtext></mml:mrow></mml:math>, Physics Letters B, Vol: 835, Pages: 137566-137566, ISSN: 0370-2693
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Evidence for WW/WZ vector boson scattering in the decay channelνqq produced in association with two jets in proton-proton collisionsat √s = 13 TeV, Physics Letters B, Vol: 834, Pages: 1-28, ISSN: 0370-2693
Evidence is reported for electroweak (EW) vector boson scattering in the decay channel νqq of twoweak vector bosons WV (V = W or Z), produced in association with two parton jets. The search usesa data set of proton-proton collisions at 13 TeV collected with the CMS detector during 2016–2018with an integrated luminosity of 138 fb−1. Events are selected requiring one lepton (electron or muon),moderate missing transverse momentum, two jets with a large pseudorapidity separation and a large dijetinvariant mass, and a signature consistent with the hadronic decay of a W/Z boson. The cross section iscomputed in a fiducial phase space defined at parton level requiring all parton transverse momentapT > 10 GeV and at least one pair of outgoing partons with invariant mass mqq > 100 GeV. The measuredand expected EW WV production cross sections are 1.90+0.53−0.46 pb and 2.23+0.08−0.11(scale) ± 0.05(PDF) pb,respectively, where PDF is the parton distribution function. The observed EW signal strength is μEW =0.85 ± 0.12 (stat)+0.19−0.17 (syst), corresponding to a signal significance of 4.4 standard deviations with 5.1expected, and it is measured keeping the quantum chromodynamics (QCD) associated diboson productionfixed to the standard model prediction. This is the first evidence of vector boson scattering in the νqqdecay channel at LHC. The simultaneous measurement of the EW and QCD associated diboson productionagrees with the standard model prediction.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Measurement of the Higgs boson width and evidence of its off-shell contributions to ZZ production, Nature Physics, Vol: 18, Pages: 1329-1334, ISSN: 1745-2473
Since the discovery of the Higgs boson in 2012, detailed studies of its properties have been ongoing. Besides its mass, its width—related to its lifetime—is an important parameter. One way to determine this quantity is to measure its off-shell production, where the Higgs boson mass is far away from its nominal value, and relating it to its on-shell production, where the mass is close to the nominal value. Here we report evidence for such off-shell contributions to the production cross-section of two Z bosons with data from the CMS experiment at the CERN Large Hadron Collider. We constrain the total rate of the off-shell Higgs boson contribution beyond the Z boson pair production threshold, relative to its standard model expectation, to the interval [0.0061, 2.0] at the 95% confidence level. The scenario with no off-shell contribution is excluded at a p-value of 0.0003 (3.6 standard deviations). We measure the width of the Higgs boson as ΓH=3.2+2.4−1.7MeV, in agreement with the standard model expectation of 4.1 MeV. In addition, we set constraints on anomalous Higgs boson couplings to W and Z boson pairs.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for a W' boson decaying to a vector-like quark and a top or bottom quark in the all-jets final state at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-46, ISSN: 1029-8479
A search is presented for a heavy W′ boson resonance decaying to a B or T vector-like quark and a t or a b quark, respectively. The analysis is performed using proton-proton collisions collected with the CMS detector at the LHC. The data correspond to an integrated luminosity of 138 fb−1 at a center-of-mass energy of 13 TeV. Both decay channels result in a signature with a t quark, a Higgs or Z boson, and a b quark, each produced with a significant Lorentz boost. The all-hadronic decays of the Higgs or Z boson and of the t quark are selected using jet substructure techniques to reduce standard model backgrounds, resulting in a distinct three-jet W′ boson decay signature. No significant deviation in data with respect to the standard model background prediction is observed. Upper limits are set at 95% confidence level on the product of the W′ boson cross section and the final state branching fraction. A W′ boson with a mass below 3.1 TeV is excluded, given the benchmark model assumption of democratic branching fractions. In addition, limits are set based on generalizations of these assumptions. These are the most sensitive limits to date for this final state.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for high-mass resonances decaying to a jet and aLorentz-boosted resonance in proton-proton collisions at √s = 13 TeV, Physics Letters B, Vol: 832, Pages: 1-24, ISSN: 0370-2693
A search is reported for high-mass hadronic resonances that decay to a parton and a Lorentz-boosted resonance, which in turn decays into a pair of partons. The search is based on data collected with the CMS detector at the LHC in proton-proton collisions at , corresponding to an integrated luminosity of 138. The boosted resonance is reconstructed as a single wide jet with substructure consistent with a two-body decay. The high-mass resonance is thus considered as a dijet system. The jet substructure information and the kinematic properties of cascade resonance decays are exploited to disentangle the signal from the large quantum chromodynamics multijet background. The dijet mass spectrum is analyzed for the presence of new high-mass resonances, and is found to be consistent with the standard model background predictions. Results are interpreted in a warped extra dimension model where the high-mass resonance is a Kaluza–Klein gluon, the boosted resonance is a radion, and the final state partons are all gluons. Limits on the production cross section are set as a function of the Kaluza–Klein gluon and radion masses. These limits exclude at 95% confidence level models with Kaluza–Klein gluon masses in the range 2.0 to 4.3 TeV and radion masses in the range 0.20 to 0.74 TeV. By exploring a novel experimental signature, the observed limits on the Kaluza–Klein gluon mass are extended by up to about 1 TeV compared to previous searches.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for Higgs boson pair production in the four b quark final state in proton-proton collisions at sqrt[s]=13 TeV, Physical Review Letters, Vol: 129, ISSN: 0031-9007
A search for pairs of Higgs bosons produced via gluon and vector boson fusion is presented, focusing on the four b quark final state. The data sample consists of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC, and corresponds to an integrated luminosity of 138 fb^{-1}. No deviation from the background-only hypothesis is observed. A 95% confidence level upper limit on the Higgs boson pair production cross section is observed at 3.9 times the standard model prediction for an expected value of 7.8. Constraints are also set on the modifiers of the Higgs field self-coupling, κ_{λ}, and of the coupling of two Higgs bosons to two vector bosons, κ_{2 V}. The observed (expected) allowed intervals at the 95% confidence level are -2.3<κ_{λ}<9.4 (-5.0<κ_{λ}<12.0) and -0.1<κ_{2 V}<2.2 (-0.4<κ_{2 V}<2.5). These are the most stringent observed constraints to date on the HH production cross section and on the κ_{2 V } coupling.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Strategies and performance of the CMS silicon tracker alignment during LHC Run 2, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment, Vol: 1037, ISSN: 0168-9002
The strategies for and the performance of the CMS silicon tracking system alignment during the 2015–2018 data-taking period of the LHC are described. The alignment procedures during and after data taking are explained. Alignment scenarios are also derived for use in the simulation of the detector response. Systematic effects, related to intrinsic symmetries of the alignment task or to external constraints, are discussed and illustrated for different scenarios.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Measurement of the Drell-Yan forward-backward asymmetry at high dilepton masses in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-58, ISSN: 1029-8479
A measurement of the forward-backward asymmetry of pairs of oppositely charged leptons (dimuons and dielectrons) produced by the Drell-Yan process in proton-proton collisions is presented. The data sample corresponds to an integrated luminosity of 138 fb−1 collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV. The asymmetry is measured as a function of lepton pair mass for masses larger than 170 GeV and compared with standard model predictions. An inclusive measurement across both channels and the full mass range yields an asymmetry of 0.612 ± 0.005 (stat) ± 0.007 (syst). As a test of lepton flavor universality, the difference between the dimuon and dielectron asymmetries is measured as well. No statistically significant deviations from standard model predictions are observed. The measurements are used to set limits on the presence of additional gauge bosons. For a Z′ boson in the sequential standard model the observed (expected) 95% confidence level lower limit on the Z′ mass is 4.4 TeV (3.7 TeV).
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for flavor-changing neutral current interactions of the top quark and Higgs Boson in final states with two photons in proton-proton collisions at sqrt[s]=13 TeV., Physical Review Letters, Vol: 129, Pages: 1-20, ISSN: 0031-9007
Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks (t) and Higgs bosons (H). The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb^{-1}. No significant excess above the background prediction is observed. Upper limits on the branching fractions (B) of the top quark decaying to a Higgs boson and an up (u) or charm (c) quark are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95% confidence level upper limits are found to be 0.019% (0.031%) for B(t→Hu) and 0.073% (0.051%) for B(t→Hc). These are the strictest upper limits yet determined.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for long-lived heavy neutral leptons with displaced vertices in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, ISSN: 1029-8479
A search for heavy neutral leptons (HNLs), the right-handed Dirac or Majorana neutrinos, is performed in final states with three charged leptons (electrons or muons) using proton-proton collision data collected by the CMS experiment at s√ = 13 TeV at the CERN LHC. The data correspond to an integrated luminosity of 138 fb−1. The HNLs could be produced through mixing with standard model neutrinos ν. For small values of the HNL mass (<20 GeV) and the square of the HNL-ν mixing parameter (10−7–10−2), the decay length of these particles can be large enough so that the secondary vertex of the HNL decay can be resolved with the CMS silicon tracker. The selected final state consists of one lepton emerging from the primary proton-proton collision vertex, and two leptons forming a displaced, secondary vertex. No significant deviations from the standard model expectations are observed, and constraints are obtained on the HNL mass and coupling strength parameters, excluding previously unexplored regions of parameter space in the mass range 1–20 GeV and squared mixing parameter values as low as 10−7.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for high-mass resonances decaying to a jet and a Lorentz-boosted resonance in proton-proton collisions at root s=13 TeV, Publisher: ELSEVIER
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Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for new physics in the lepton plus missing transverse momentum final state in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-57, ISSN: 1029-8479
A search for physics beyond the standard model (SM) in final states withan electron or muon and missing transverse momentum is presented. The analysis usesdata from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with theCMS detector at the LHC in 2016–2018 and corresponding to an integrated luminosity of138 fb−1. No significant deviation from the SM prediction is observed. Model-independentlimits are set on the production cross section of W’ bosons decaying into lepton-plusneutrino final states. Within the framework of the sequential standard model, with thecombined results from the electron and muon decay channels a W’ boson with mass lessthan 5.7 TeV is excluded at 95% confidence level. Results on a SM precision test, thedetermination of the oblique electroweak W parameter, are presented using LHC datafor the first time. These results together with those from the direct W’ resonance searchare used to extend existing constraints on composite Higgs scenarios. This is the firstexperimental exclusion on compositeness parameters using results from LHC data otherthan Higgs boson measurements
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for resonances decaying to three W bosons in proton-proton collisions at sqrt[s]=13 TeV, Physical Review Letters, Vol: 129, ISSN: 0031-9007
A search for resonances decaying into a W boson and a radion, where the radion decays into two W bosons, is presented. The data analyzed correspond to an integrated luminosity of 138 fb^{-1} recorded in proton-proton collisions with the CMS detector at sqrt[s]=13 TeV. One isolated charged lepton is required, together with missing transverse momentum and one or two massive large-radius jets, containing the decay products of either two or one W bosons, respectively. No excess over the background estimation is observed. The results are combined with those from a complementary channel with an all-hadronic final state, described in an accompanying paper. Limits are set on parameters of an extended warped extra-dimensional model. These searches are the first of their kind at the LHC.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Probing charm quark dynamics via multiparticle correlations in Pb-Pb collisions at sqrt[s_{NN}]=5.02 TeV, Physical Review Letters, Vol: 129, ISSN: 0031-9007
Multiparticle azimuthal correlations of prompt D^{0} mesons are measured in Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of sqrt[s_{NN}]=5.02 TeV. For the first time, a four-particle cumulant method is used to extract the second Fourier coefficient of the azimuthal distribution (v_{2}) of D^{0} mesons as a function of event centrality and the D^{0} transverse momentum. The ratios of the four-particle v_{2} values to previously measured two-particle cumulant results provide direct experimental access to event-by-event fluctuations of charm quark azimuthal anisotropies. These ratios are also found to be comparable to those of inclusive charged particles in the event. However, hints of deviations are seen in the most central and peripheral collisions. To investigate the origin of flow fluctuations in the charm sector, these measurements are compared to a model implementing fluctuations of charm quark energy loss via collisional or radiative processes in the quark-gluon plasma. These models cannot quantitatively describe the data over the full transverse momentum and centrality ranges, although the calculations with collisional energy loss provide a better description of the data.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for resonances decaying to three W bosons in the hadronic final state in proton-proton collisions at ps=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 106, ISSN: 1550-2368
A search for Kaluza-Klein excited vector boson resonances, WKK, decaying in cascade to three W bosons via a scalar radion R, WKK→WR→WWW, in a final state containing two or three massive jets is presented. The search is performed with √s=13 TeV proton-proton collision data collected by the CMS experiment at the CERN LHC during 2016–2018, corresponding to an integrated luminosity of 138 fb−1. Two final states are simultaneously probed, one where the two W bosons produced by the R decay are reconstructed as separate, large-radius, massive jets, and one where they are merged into a single large-radius jet. The observed data are in agreement with the standard model expectations. Limits are set on the product of the WKK resonance cross section and branching fraction to three W bosons in an extended warped extra-dimensional model and are the first of their kind at the LHC.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Measurement of the inclusive and differential WZ production cross sections, polarization angles, and triple gauge couplings in pp collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-78, ISSN: 1029-8479
The associated production of a W and a Z boson is studied in final states with multiple leptons produced in proton-proton (pp) collisions at a centre-of-mass energy of 13 TeV using 137 fb−1 of data collected with the CMS detector at the LHC. A measurement of the total inclusive production cross section yields σtot(pp → WZ) = 50.6 ± 0.8 (stat) ± 1.5 (syst) ± 1.1 (lumi) ± 0.5 (theo) pb. Measurements of the fiducial and differential cross sections for several key observables are also performed in all the final-state lepton flavour and charge compositions with a total of three charged leptons, which can be electrons or muons. All results are compared with theoretical predictions computed up to next-to-next-to-leading order in quantum chromodynamics plus next-to-leading or- der in electroweak theory and for various sets of parton distribution functions. The results include direct measurements of the charge asymmetry and the W and Z vector boson polarization. The first observation of longitudinally polarized W bosons in WZ production is reported. Anomalous gauge couplings are searched for, leading to new constraints on beyond-the-standard-model contributions to the WZ triple gauge coupling.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Identification of hadronic tau lepton decays using a deep neural network, Journal of Instrumentation, Vol: 17, Pages: 1-53, ISSN: 1748-0221
A new algorithm is presented to discriminate reconstructed hadronic decays of tau leptons (τh) that originate from genuine tau leptons in the CMS detector against τh candidates that originate from quark or gluon jets, electrons, or muons. The algorithm inputs information from all reconstructed particles in the vicinity of a τh candidate and employs a deep neural network with convolutional layers to efficiently process the inputs. This algorithm leads to a significantly improved performance compared with the previously used one. For example, the efficiency for a genuine τh to pass the discriminator against jets increases by 10–30% for a given efficiency for quark and gluon jets. Furthermore, a more efficient τh reconstruction is introduced that incorporates additional hadronic decay modes. The superior performance of the new algorithm to discriminate against jets, electrons, and muons and the improved τh reconstruction method are validated with LHC proton-proton collision data at √s = 13 TeV.
Tumasyan A, Adam W, Bergauer T, et al., 2022, First search for exclusive diphoton production at high mass with tagged protons in proton-proton collisions at sqrt[s]=13 TeV, Physical Review Letters, Vol: 129, ISSN: 0031-9007
A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp→pγγp with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb^{-1} collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons match the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% confidence level are |ζ_{1}|<2.9×10^{-13} GeV^{-4} and |ζ_{2}|<6.0×10^{-13} GeV^{-4}.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for resonant production of strongly coupled dark matter in proton-proton collisions at 13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-51, ISSN: 1029-8479
The first collider search for dark matter arising from a strongly coupled hidden sector is presented and uses a data sample corresponding to 138 fb−1, collected with the CMS detector at the CERN LHC, at s√ = 13 TeV. The hidden sector is hypothesized to couple to the standard model (SM) via a heavy leptophobic Z′ mediator produced as a resonance in proton-proton collisions. The mediator decay results in two “semivisible” jets, containing both visible matter and invisible dark matter. The final state therefore includes moderate missing energy aligned with one of the jets, a signature ignored by most dark matter searches. No structure in the dijet transverse mass spectra compatible with the signal is observed. Assuming the Z′ boson has a universal coupling of 0.25 to the SM quarks, an inclusive search, relevant to any model that exhibits this kinematic behavior, excludes mediator masses of 1.5–4.0 TeV at 95% confidence level, depending on the other signal model parameters. To enhance the sensitivity of the search for this particular class of hidden sector models, a boosted decision tree (BDT) is trained using jet substructure variables to distinguish between semivisible jets and SM jets from background processes. When the BDT is employed to identify each jet in the dijet system as semivisible, the mediator mass exclusion increases to 5.1 TeV, for wider ranges of the other signal model parameters. These limits exclude a wide range of strongly coupled hidden sector models for the first time.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Observation of the B_{c}^{+} meson in Pb-Pb and pp collisions at sqrt[s_{NN}]=5.02 TeV and measurement of its nuclear modification factor, Physical Review Letters, Vol: 128, ISSN: 0031-9007
The B_{c}^{+} meson is observed for the first time in heavy ion collisions. Data from the CMS detector are used to study the production of the B_{c}^{+} meson in lead-lead (Pb-Pb) and proton-proton (pp) collisions at a center-of-mass energy per nucleon pair of sqrt[s_{NN}]=5.02 TeV, via the B_{c}^{+}→(J/ψ→μ^{+}μ^{-})μ^{+}ν_{μ} decay. The B_{c}^{+} nuclear modification factor, derived from the Pb-Pb-to-pp ratio of production cross sections, is measured in two bins of the trimuon transverse momentum and of the Pb-Pb collision centrality. The B_{c}^{+} meson is shown to be less suppressed than quarkonia and most of the open heavy-flavor mesons, suggesting that effects of the hot and dense nuclear matter created in heavy ion collisions contribute to its production. This measurement sets forth a promising new probe of the interplay of suppression and enhancement mechanisms in the production of heavy-flavor mesons in the quark-gluon plasma.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for charged-lepton flavor violation in top quark production and decay in pp collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-43, ISSN: 1029-8479
Results are presented from a search for charged-lepton flavor violating (CLFV) interactions in top quark production and decay in pp collisions at a center-of-mass energy of 13 TeV. The events are required to contain one oppositely charged electron-muon pair in the final state, along with at least one jet identified as originating from a bottom quark. The data correspond to an integrated luminosity of 138 fb−1, collected by the CMS experiment at the LHC. This analysis includes both the production (q → eμt) and decay (t → eμq) modes of the top quark through CLFV interactions, with q referring to a u or c quark. These interactions are parametrized using an effective field theory approach. With no significant excess over the standard model expectation, the results are interpreted in terms of vector-, scalar-, and tensor-like CLFV four-fermion effective interactions. Finally, observed exclusion limits are set at 95% confidence levels on the respective branching fractions of a top quark to an eμ pair and an up (charm) quark of 0.13 × 10−6 (1.31 × 10−6), 0.07 × 10−6 (0.89 × 10−6), and 0.25 × 10−6 (2.59 × 10−6) for vector, scalar, and tensor CLFV interactions, respectively.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Inclusive nonresonant multilepton probes of new phenomena at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 105, ISSN: 1550-2368
An inclusive search for nonresonant signatures of beyond the standard model (SM) phenomena in events with three or more charged leptons, including hadronically decaying τ leptons, is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 138 fb−1 of proton-proton collisions at √s=13 TeV, collected by the CMS experiment at the LHC in 2016–2018. Events are categorized based on the lepton and b-tagged jet multiplicities and various kinematic variables. Three scenarios of physics beyond the SM are probed, and signal-specific boosted decision trees are used for enhancing sensitivity. No significant deviations from the background expectations are observed. Lower limits are set at 95% confidence level on the mass of type-III seesaw heavy fermions in the range 845–1065 GeV for various decay branching fraction combinations to SM leptons. Doublet and singlet vectorlike τ lepton extensions of the SM are excluded for masses below 1045 GeV and in the mass range 125–150 GeV, respectively. Scalar leptoquarks decaying exclusively to a top quark and a lepton are excluded below 1.12–1.42 TeV, depending on the lepton flavor. For the type-III seesaw as well as the vectorlike doublet model, these constraints are the most stringent to date. For the vectorlike singlet model, these are the first constraints from the LHC experiments. Detailed results are also presented to facilitate alternative theoretical interpretations.
Tumasyan A, Adam W, Ambrogi F, et al., 2022, Observation of B-s(0) mesons and measurement of the B-s(0)/B+ yield ratio in PbPb collisions at root S-NN=5.02 TeV, Modern Physics Letters B, Vol: 829, Pages: 1-25, ISSN: 0217-9849
The B0s and B+ production yields are measured in PbPb collisions at a center-of-mass energy pernucleon pair of 5.02 TeV. The data sample, collected with the CMS detector at the LHC, correspondsto an integrated luminosity of 1.7 nb−1. The mesons are reconstructed in the exclusive decay channelsB0s → J/ψ(μ+μ−)φ(K+K−) and B+ → J/ψ(μ+μ−)K+, in the transverse momentum range 7–50 GeV/cand absolute rapidity 0–2.4. The B0s meson is observed with a statistical significance in excess of fivestandard deviations for the first time in nucleus-nucleus collisions. The measurements are performed asfunctions of the transverse momentum of the B mesons and of the PbPb collision centrality. The ratioof production yields of B0s and B+ is measured and compared to theoretical models that include quarkrecombination effects.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Analysis of the CP structure of the Yukawa coupling between the Higgs boson and tau leptons in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-67, ISSN: 1029-8479
The first measurement of the CP structure of the Yukawa coupling between the Higgs boson and τ leptons is presented. The measurement is based on data collected in proton-proton collisions at 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 τ leptons produced in Higgs boson decays. The effective mixing angle between CP-even and CP-odd τ Yukawa couplings is found to be −1 ± 19°, compared to an expected value of 0 ± 21° 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.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Observation of B-0 ->psi(2S)K-S(0)pi(+)pi(-) and B-s(0)->psi(2S)K-S(0) decays, Publisher: SPRINGER
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Measurement of the production cross section for Z plus b jets in proton-proton collisions at ?s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 105, ISSN: 1550-2368
The measurement of the cross section for the production of a Z boson, decaying to dielectrons or dimuons, in association with at least one bottom quark jet is performed with proton-proton collision data at √s=13 TeV. The data sample corresponds to an integrated luminosity of 137 fb−1, collected by the CMS experiment at the LHC during 2016–2018. The integrated cross sections for Z+≥1 b jet and Z+≥2 b jets are reported for the electron, muon, and combined channels. The fiducial cross sections in the combined channel are 6.52±0.04(stat)±0.40(syst)±0.14(theo) pb for Z+≥1 b jet and 0.65±0.03(stat)±0.07(syst)±0.02(theo) pb for Z+≥2 b jets. The differential cross section distributions are measured as functions of various kinematic observables that are useful for precision tests of perturbative quantum chromodynamics predictions. The ratios of integrated and differential cross sections for Z+≥2b jets and Z+≥1 b jet processes are also determined. The value of the integrated cross section ratio measured in the combined channel is 0.100±0.005(stat)±0.007(syst)±0.003(theo). All measurements are compared with predictions from various event generators.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Observation of B 0 → ψ (2S)K S 0 π + π - and B s 0 → ψ (2S)K S 0 decays, Eur Phys J C Part Fields, Vol: 82, ISSN: 1434-6044
Using a data sample of s√=13TeV proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of 103~fb−1, the B0s→ψ(2S)K0S and B0→ψ(2S)K0Sπ+π− decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to B(B0s→ψ(2S)K0S)/B(B0→ψ(2S)K0S)=(3.33±0.69(stat)±0.11(syst)±0.34(fs/fd))×10−2 and B(B0→ψ(2S)K0Sπ+π−)/B(B0→ψ(2S)K0S)=0.480±0.013(stat)±0.032(syst), where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of B0s and B0 mesons, fs/fd.
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