Displaying publications 1 - 20 of 199 in total

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  1. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Dec 29;131(26):262301.
    PMID: 38215362 DOI: 10.1103/PhysRevLett.131.262301
    Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent J/ψ photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon (W_{γN}^{Pb}) over a wide range of 40
  2. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Oct 13;131(15):151803.
    PMID: 37897747 DOI: 10.1103/PhysRevLett.131.151803
    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}.
  3. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Sep 22;131(12):121901.
    PMID: 37802954 DOI: 10.1103/PhysRevLett.131.121901
    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.
  4. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Sep 08;131(10):101801.
    PMID: 37739361 DOI: 10.1103/PhysRevLett.131.101801
    We present the first direct search for exotic Higgs boson decays H→AA, A→γγ in events with two photonlike objects. The hypothetical particle A is a low-mass spin-0 particle decaying promptly to a merged diphoton reconstructed as a single photonlike object. We analyze the data collected by the CMS experiment at sqrt[s]=13  TeV corresponding to an integrated luminosity of 136  fb^{-1}. No excess above the estimated background is found. We set upper limits on the branching fraction B(H→AA→4γ) of (0.9-3.3)×10^{-3} at 95% confidence level for masses of A in the range 0.1-1.2 GeV.
  5. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Sep 01;131(9):091803.
    PMID: 37721845 DOI: 10.1103/PhysRevLett.131.091803
    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.
  6. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Aug 11;131(6):061801.
    PMID: 37625071 DOI: 10.1103/PhysRevLett.131.061801
    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
  7. Tumasyan A, Adam W, Bergauer T, Dragicevic M, Del Valle AE, Frühwirth R, et al.
    Phys Rev Lett, 2023 Aug 04;131(5):051901.
    PMID: 37595238 DOI: 10.1103/PhysRevLett.131.051901
    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.
  8. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Jul 28;131(4):041803.
    PMID: 37566864 DOI: 10.1103/PhysRevLett.131.041803
    A search for nonresonant Higgs boson (H) pair production via gluon and vector boson (V) fusion is performed in the four-bottom-quark final state, using proton-proton collision data at 13 TeV corresponding to 138  fb^{-1} collected by the CMS experiment at the LHC. The analysis targets Lorentz-boosted H pairs identified using a graph neural network. It constrains the strengths relative to the standard model of the H self-coupling and the quartic VVHH couplings, κ_{2V}, excluding κ_{2V}=0 for the first time, with a significance of 6.3 standard deviations when other H couplings are fixed to their standard model values.
  9. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Jul 28;131(4):041801.
    PMID: 37566854 DOI: 10.1103/PhysRevLett.131.041801
    A search for the standard model (SM) Higgs boson (H) produced with transverse momentum (p_{T}) greater than 450 GeV and decaying to a charm quark-antiquark (cc[over ¯]) pair is presented. The search is performed using proton-proton collision data collected at sqrt[s]=13  TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 138  fb^{-1}. Boosted H→cc[over ¯] decay products are reconstructed as a single large-radius jet and identified using a deep neural network charm tagging technique. The method is validated by measuring the Z→cc[over ¯] decay process, which is observed in association with jets at high p_{T} for the first time with a signal strength of 1.00_{-0.14}^{+0.17}(syst)±0.08(theo)±0.06(stat), defined as the ratio of the observed process rate to the SM expectation. The observed (expected) upper limit on σ(H)B(H→cc[over ¯]) is set at 47 (39) times the SM prediction at 95% confidence level.
  10. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Phys Rev Lett, 2023 Jul 07;131(1):011803.
    PMID: 37478454 DOI: 10.1103/PhysRevLett.131.011803
    The first search exploiting the vector boson fusion process to probe heavy Majorana neutrinos and the Weinberg operator at the LHC is presented. The search is performed in the same-sign dimuon final state using a proton-proton collision dataset recorded at sqrt[s]=13  TeV, collected with the CMS detector and corresponding to a total integrated luminosity of 138  fb^{-1}. The results are found to agree with the predictions of the standard model. For heavy Majorana neutrinos, constraints on the squared mixing element between the muon and the heavy neutrino are derived in the heavy neutrino mass range 50 GeV-25 TeV; for masses above 650 GeV these are the most stringent constraints from searches at the LHC to date. A first test of the Weinberg operator at colliders provides an observed upper limit at 95% confidence level on the effective μμ Majorana neutrino mass of 10.8 GeV.
  11. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Eur Phys J C Part Fields, 2023;83(8):722.
    PMID: 37578844 DOI: 10.1140/epjc/s10052-023-11833-z
    The 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 36.3fb-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 10GeV to higher than 100GeV. The azimuthal correlation Δϕ 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.
  12. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Eur Phys J C Part Fields, 2023;83(7):587.
    PMID: 37440247 DOI: 10.1140/epjc/s10052-023-11630-8
    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 s=7 and 13TeV, and by the CDF experiment at 1.96TeV 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 13TeV including measurements of the underlying-event, strange-particle multiplicities, jet substructure observables, jet shapes, and colour flow in top quark pair (tt¯) 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 tt¯ events in the semileptonic channel at 13TeV.
  13. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Eur Phys J C Part Fields, 2023;83(10):933.
    PMID: 37855556 DOI: 10.1140/epjc/s10052-023-11952-7
    A 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 138fb-1. The 95% confidence level upper limit set on the branching fraction of the 125GeV 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 13TeV in complementary production modes. The combined upper limit at 95% confidence level on B(H→inv) is 0.15 (0.08 expected).
  14. Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Damanakis K, et al.
    Eur Phys J C Part Fields, 2023;83(10):963.
    PMID: 37906635 DOI: 10.1140/epjc/s10052-023-12050-4
    The mass of the top quark is measured in 36.3fb-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.
  15. Koly KN, Tasnim Z, Ahmed S, Saba J, Mahmood R, Farin FT, et al.
    BMC Psychiatry, 2022 Dec 19;22(1):797.
    PMID: 36529761 DOI: 10.1186/s12888-022-04414-z
    BACKGROUND: Mental health remains a highly stigmatized area of healthcare, and people often conceal their concerns rather than seek assistance or treatment. The Women Support Initiative Forum (WSIF) is a social media platform established in 2018 to provide expert and peer-led psychosocial support services to women of all ages in Bangladesh. The anonymous nature of the forum means that mental health concerns can be aired without fear of identification.

    METHOD: A content analysis was conducted on the anonymous posts retrieved from the WSIF platform between 8th March 2020 and 7th July 2022. Around 1457 posts were initially selected for analysis which was reduced to 1006 after removing duplicates and non-relevant posts, such as queries about the addresses of the doctors and other non-mental health-related issues. A thematic analysis of the data was conducted using an inductive approach.

    RESULT: The 1006 posts generated four themes and nine sub-themes. All the women mentioned mental health symptoms (n = 1006; 100%). Most also mentioned reasons for seeking mental healthcare (n = 818; 81.31%), healthcare-seeking behavior (n = 667; 66.30%), and barriers to seeking mental healthcare (n = 552; 54.87%). The majority of women described symptoms of stress, depression, and anxiety-like symptoms, which were aggregated under common mental health conditions. Mental health symptoms were ascribed to various external influences, including marital relationship, intrafamilial abuse, and insecurities related to the COVID-19 pandemic. A large proportion of posts were related to women seeking information about mental healthcare services and service providers (psychologists or psychiatrists). The analysis found that most women did not obtain mental healthcare services despite their externalized mental health symptoms. The posts identified clear barriers to women accessing mental health services, including low mental health literacy, the stigma associated with mental healthcare-seeking behavior, and the poor availability of mental health care services.

    CONCLUSION: The study revealed that raising mass awareness and designing culturally acceptable evidence-based interventions with multisectoral collaborations are crucial to ensuring better mental healthcare coverage for women in Bangladesh.

  16. Murthy V, Sethuraman KR, Choudhury S, Shakila R
    Int J Psychiatry Med, 2022 Mar;57(2):117-133.
    PMID: 33472469 DOI: 10.1177/0091217421990142
    OBJECTIVE: Communication skills diminish with time and must be applied and updated frequently. Due to various professional constraints, the dentists may not be able to attend training programs to sharpen their skills. During patient interactions, dentists may face difficult situations which they may be unable to handle and, consequently, make them overreact. Therefore, there is a need to provide a platform to freely discuss their feelings, ideas, and take opinion from peers.

    METHODS: Training in communication skills customized for dealing with complete denture patients was conducted for the prosthodontic postgraduates. Based on feedback obtained, it was decided to have periodic meetings and the concept of Practice-Oriented-Peer Review for Prosthodontics (PrO-PReP) was introduced. This novel concept is a combination of the Relationship building, exploring Reactions, exploring Content, and Coaching (R2C2) model of residency education and the Balint method. The meetings were scheduled every one or two months based on the available caseload of the patients treated by the postgraduates.

    RESULTS: The thematic analysis of the postgraduates' self-reflection during the sessions and the video recorded observations (assessed using the Kalamazoo scale) revealed that these sessions were effective in positively engaging the postgraduates to discuss their experiences, reflect on their performances, practice their newly gained skills, and learn from peer sharing.

    CONCLUSION: The postgraduates felt that they have changed in their working style and were more confident to manage patients. They found such sessions very useful for being updated with the already-learned skills.

  17. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, Dragicevic M, et al.
    Phys Rev Lett, 2022 Jan 21;128(3):032001.
    PMID: 35119878 DOI: 10.1103/PhysRevLett.128.032001
    The first evidence for X(3872) production in relativistic heavy ion collisions is reported. The X(3872) production is studied in lead-lead (Pb-Pb) collisions at a center-of-mass energy of sqrt[s_{NN}]=5.02  TeV per nucleon pair, using the decay chain X(3872)→J/ψπ^{+}π^{-}→μ^{+}μ^{-}π^{+}π^{-}. The data were recorded with the CMS detector in 2018 and correspond to an integrated luminosity of 1.7  nb^{-1}. The measurement is performed in the rapidity and transverse momentum ranges |y|<1.6 and 15
  18. Sirunyan AM, Tumasyan A, Adam W, Bergauer T, Dragicevic M, Erö J, et al.
    Phys Rev Lett, 2021 Sep 17;127(12):122001.
    PMID: 34597080 DOI: 10.1103/PhysRevLett.127.122001
    The first measurement of the dependence of γγ→μ^{+}μ^{-} production on the multiplicity of neutrons emitted very close to the beam direction in ultraperipheral heavy ion collisions is reported. Data for lead-lead interactions at sqrt[s_{NN}]=5.02  TeV, with an integrated luminosity of approximately 1.5  nb^{-1}, are collected using the CMS detector at the LHC. The azimuthal correlations between the two muons in the invariant mass region 88.3. The back-to-back correlation structure from leading-order photon-photon scattering is found to be significantly broader for events with a larger number of emitted neutrons from each nucleus, corresponding to interactions with a smaller impact parameter. This observation provides a data-driven demonstration that the average transverse momentum of photons emitted from relativistic heavy ions has an impact parameter dependence. These results provide new constraints on models of photon-induced interactions in ultraperipheral collisions. They also provide a baseline to search for possible final-state effects on lepton pairs caused by traversing a quark-gluon plasma produced in hadronic heavy ion collisions.
  19. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, Dragicevic M, et al.
    Phys Rev Lett, 2021 Sep 03;127(10):102002.
    PMID: 34533355 DOI: 10.1103/PhysRevLett.127.102002
    The CMS experiment at the LHC has measured the differential cross sections of Z bosons decaying to pairs of leptons, as functions of transverse momentum and rapidity, in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02  TeV. The measured Z boson elliptic azimuthal anisotropy coefficient is compatible with zero, showing that Z bosons do not experience significant final-state interactions in the medium produced in the collision. Yields of Z bosons are compared to Glauber model predictions and are found to deviate from these expectations in peripheral collisions, indicating the presence of initial collision geometry and centrality selection effects. The precision of the measurement allows, for the first time, for a data-driven determination of the nucleon-nucleon integrated luminosity as a function of lead-lead centrality, thereby eliminating the need for its estimation based on a Glauber model.
  20. Sirunyan AM, Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, et al.
    Phys Rev Lett, 2021 Jun 25;126(25):252003.
    PMID: 34241504 DOI: 10.1103/PhysRevLett.126.252003
    The Ξ_{b}^{-}π^{+}π^{-} invariant mass spectrum is investigated with an event sample of proton-proton collisions at sqrt[s]=13  TeV, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 140  fb^{-1}. The ground state Ξ_{b}^{-} is reconstructed via its decays to J/ψΞ^{-} and J/ψΛK^{-}. A narrow resonance, labeled Ξ_{b}(6100)^{-}, is observed at a Ξ_{b}^{-}π^{+}π^{-} invariant mass of 6100.3±0.2(stat)±0.1(syst)±0.6(Ξ_{b}^{-})  MeV, where the last uncertainty reflects the precision of the Ξ_{b}^{-} baryon mass. The upper limit on the Ξ_{b}(6100)^{-} natural width is determined to be 1.9  MeV at 95% confidence level. The low Ξ_{b}(6100)^{-} signal yield observed in data does not allow a measurement of the quantum numbers of the new state. However, following analogies with the established excited Ξ_{c} baryon states, the new Ξ_{b}(6100)^{-} resonance and its decay sequence are consistent with the orbitally excited Ξ_{b}^{-} baryon, with spin and parity quantum numbers J^{P}=3/2^{-}.
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