Person: KAYA, MİTHAT
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KAYA
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MİTHAT
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Publication Metadata only A multi-dimensional search for new heavy resonances decaying to boosted WW , WZ , or ZZ boson pairs in the dijet final state at 13 Te(2020-03-01) KAYA, MİTHAT; Sirunyan A., Tumasyan A., Adam W., Ambrogi F., Bergauer T., Brandstetter J., Dragicevic M., Erö J., Del Valle A. E., Flechl M., et al.© 2020, CERN for the benefit of the CMS collaboration.A search in an all-jet final state for new massive resonances decaying to WW, WZ, or ZZ boson pairs using a novel analysis method is presented. The analysis is performed on data corresponding to an integrated luminosity of 77.3 fb-1 recorded with the CMS experiment at the LHC at a centre-of-mass energy of 13 Te. The search is focussed on potential narrow-width resonances with masses above 1.2 Te, where the decay products of each W or Z boson are expected to be collimated into a single, large-radius jet. The signal is extracted using a three-dimensional maximum likelihood fit of the two jet masses and the dijet invariant mass, yielding an improvement in sensitivity of up to 30% relative to previous search methods. No excess is observed above the estimated standard model background. In a heavy vector triplet model, spin-1 Z ′ and W ′ resonances with masses below 3.5 and 3.8 Te, respectively, are excluded at 95% confidence level. In a bulk graviton model, upper limits on cross sections are set between 27 and 0.2 fb for resonance masses between 1.2 and 5.2 Te, respectively. The limits presented in this paper are the best to date in the dijet final state.Publication Metadata only Combined searches for the production of supersymmetric top quark partners in proton–proton collisions at √s=13Te(2021-11-01) KAYA, MİTHAT; Tumasyan A., Adam W., Andrejkovic J., Bergauer T., Chatterjee S., Dragicevic M., Del Valle A. E., Frühwirth R., Jeitler M., Krammer N., et al.© 2021, The Author(s).A combination of searches for top squark pair production using proton–proton collision data at a center-of-mass energy of 13Te at the CERN LHC, corresponding to an integrated luminosity of 137fb-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 the model, the combined result excludes a top squark mass up to 1325Ge for a massless neutralino, and a neutralino mass up to 700Ge for a top squark mass of 1150Ge. Top squarks with masses from 145 to 295Ge, for neutralino masses from 0 to 100Ge, with a mass difference between the top squark and the neutralino in a window of 30Ge 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 420Ge.Publication Metadata only Search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks in proton–proton collisions at √s=13Te(2019-03-01) KAYA, MİTHAT; Sirunyan A., Tumasyan A., Adam W., Ambrogi F., Asilar E., Bergauer T., Brandstetter J., Dragicevic M., Erö J., Del Valle A. E., et al.© 2019, CERN for the benefit of the CMS collaboration. A search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks is performed in proton–proton collisions at a center-of-mass energy of 13Te collected with the CMS detector at the LHC. The analyzed data sample corresponds to an integrated luminosity of 35.9fb-1. The signal is characterized by a large missing transverse momentum recoiling against a bottom quark–antiquark system that has a large Lorentz boost. The number of events observed in the data is consistent with the standard model background prediction. Results are interpreted in terms of limits both on parameters of the type-2 two-Higgs doublet model extended by an additional light pseudoscalar boson a (2HDM+a) and on parameters of a baryonic Z ′ simplified model. The 2HDM+a model is tested experimentally for the first time. For the baryonic Z ′ model, the presented results constitute the most stringent constraints to date.Publication Metadata only Inclusive and differential cross section measurements of single top quark production in association with a Z boson in proton-proton collisions at √s = 13 TeV(2022-02-01) KAYA, MİTHAT; Tumasyan A., Adam W., Andrejkovic J., Bergauer T., Chatterjee S., Damanakis K., Dragicevic M., Escalante Del Valle A., Frühwirth R., Jeitler M., et al.© 2022, The Author(s).Inclusive and differential cross sections of single top quark production in association with a Z boson are measured in proton-proton collisions at a center-of-mass energy of 13 TeV with a data sample corresponding to an integrated luminosity of 138 fb−1 recorded by the CMS experiment. Events are selected based on the presence of three leptons, electrons or muons, associated with leptonic Z boson and top quark decays. The measurement yields an inclusive cross section of 87.9−7.3+7.5(stat)−6.0+7.3(syst) fb for a dilepton invariant mass greater than 30 GeV, in agreement with standard model (SM) calculations and represents the most precise determination to date. The ratio between the cross sections for the top quark and the top antiquark production in association with a Z boson is measured as 2.37−0.42+0.56(stat)−0.13+0.27(syst). Differential measurements at parton and particle levels are performed for the first time. Several kinematic observables are considered to study the modeling of the process. Results are compared to theoretical predictions with different assumptions on the source of the initial-state b quark and found to be in agreement, within the uncertainties. Additionally, the spin asymmetry, which is sensitive to the top quark polarization, is determined from the differential distribution of the polarization angle at parton level to be 0.54 ± 0.16 (stat) ± 0.06 (syst), in agreement with SM predictions. [Figure not available: see fulltext.]Publication Metadata only 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(2023-09-10) KAYA, MİTHAT; Tumasyan A., Adam W., Andrejkovic J., Bergauer T., Chatterjee S., Damanakis K., Dragicevic M., Escalante Del Valle A., Hussain P., Jeitler M., et al.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.Publication Metadata only Measurements of angular distance and momentum ratio distributions in three-jet and Z + two-jet final states in pp collisions(2021-09-01) KAYA, MİTHAT; Sirunyan A., Tumasyan A., Adam W., Bergauer T., Dragicevic M., Erö J., Valle A. E. D., Frühwirth R., Jeitler M., Krammer N., et al.© 2021, The Author(s).Collinear (small-angle) and large-angle, as well as soft and hard radiations are investigated in three-jet and Z + two-jet events collected in proton-proton collisions at the LHC. The normalized production cross sections are measured as a function of the ratio of transverse momenta of two jets and their angular separation. The measurements in the three-jet and Z + two-jet events are based on data collected at a center-of-mass energy of 8TeV, corresponding to an integrated luminosity of 19.8fb-1. The Z + two-jet events are reconstructed in the dimuon decay channel of the Z boson. The three-jet measurement is extended to include s=13TeV data corresponding to an integrated luminosity of 2.3fb-1. The results are compared to predictions from event generators that include parton showers, multiple parton interactions, and hadronization. The collinear and soft regions are in general well described by parton showers, whereas the regions of large angular separation are often best described by calculations using higher-order matrix elements.Publication Metadata only Search for a heavy composite Majorana neutrino in events with dilepton signatures from proton-proton collisions at s=13 TeV(2023-08-10) KAYA, MİTHAT; Tumasyan A., Adam W., Andrejkovic J., Bergauer T., Chatterjee S., Damanakis K., Dragicevic M., Escalante Del Valle A., Hussain P., Jeitler M., et al.Results are presented of a search for a heavy Majorana neutrino [Formula presented] decaying into two same-flavor leptons ℓ (electrons or muons) and a quark-pair jet. A model is considered in which the [Formula presented] is an excited neutrino in a compositeness scenario. The analysis is performed using a sample of proton-proton collisions at s=13TeV recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 138fb−1. The data are found to be in agreement with the standard model prediction. For the process in which the [Formula presented] is produced in association with a lepton, followed by the decay of the [Formula presented] to a same-flavor lepton and a quark pair, an upper limit at 95% confidence level on the product of the cross section and branching fraction is obtained as a function of the [Formula presented] mass [Formula presented] and the compositeness scale Λ. For this model the data exclude the existence of [Formula presented] ([Formula presented]) for [Formula presented] below 6.0 (6.1) TeV, at the limit where [Formula presented] is equal to Λ. For [Formula presented], values of Λ less than 20 (23) TeV are excluded. These results represent a considerable improvement in sensitivity, covering a larger parameter space than previous searches in [Formula presented] collisions at 13 TeV.Publication Metadata only Combined measurements of Higgs boson couplings in proton–proton collisions at √s=13Te(2019-05-01) KAYA, MİTHAT; Sirunyan A., Tumasyan A., Adam W., Ambrogi F., Asilar E., Bergauer T., Brandstetter J., Dragicevic M., Erö J., Del Valle A. E. , et al.© 2019, CERN for the benefit of the CMS collaboration.Combined measurements of the production and decay rates of the Higgs boson, as well as its couplings to vector bosons and fermions, are presented. The analysis uses the LHC proton–proton collision data set recorded with the CMS detector in 2016 at s=13Te, corresponding to an integrated luminosity of 35.9fb-1. The combination is based on analyses targeting the five main Higgs boson production mechanisms (gluon fusion, vector boson fusion, and associated production with a W or Z boson, or a top quark-antiquark pair) and the following decay modes: H → γγ, Z Z , W W , ττ, b b , and μμ. Searches for invisible Higgs boson decays are also considered. The best-fit ratio of the signal yield to the standard model expectation is measured to be μ= 1.17 ± 0.10 , assuming a Higgs boson mass of 125.09Ge. Additional results are given for various assumptions on the scaling behavior of the production and decay modes, including generic parametrizations based on ratios of cross sections and branching fractions or couplings. The results are compatible with the standard model predictions in all parametrizations considered. In addition, constraints are placed on various two Higgs doublet models.Publication Metadata only Study of dijet events with large rapidity separation in proton-proton collisions at √s = 2.76 TeV(2022-03-01) KAYA, MİTHAT; Tumasyan A., Adam W., Andrejkovic J., Bergauer T., Chatterjee S., Dragicevic M., Escalante Del Valle A., Frühwirth R., Jeitler M., Krammer N., et al.© 2022, The Author(s).The cross sections for inclusive and Mueller-Navelet dijet production are measured as a function of the rapidity separation between the jets in proton-proton collisions at s = 2.76 TeV for jets with transverse momentum pT> 35 GeV and rapidity |y| 20 GeV is introduced to improve the sensitivity to the effects of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution. The measurement is compared with the predictions of various Monte Carlo models based on leading-order and next-to-leading-order calculations including the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi leading-logarithm (LL) parton shower as well as the LL BFKL resummation. [Figure not available: see fulltext.]Publication Metadata only Measurement of differential cross sections and charge ratios for t-channel single top quark production in proton–proton collisions at √s=13Te(2020-05-01) KAYA, MİTHAT; Sirunyan A., Tumasyan A., Adam W., Ambrogi F., Bergauer T., Brandstetter J., Dragicevic M., Erö J., Del Valle A. E., Flechl M., et al.© 2020, CERN for the benefit of the CMS collaboration.A measurement is presented of differential cross sections for t-channel single top quark and antiquark production in proton–proton collisions at a centre-of-mass energy of 13Te by the CMS experiment at the LHC. From a data set corresponding to an integrated luminosity of 35.9fb-1, events containing one muon or electron and two or three jets are analysed. The cross section is measured as a function of the top quark transverse momentum (pT), rapidity, and polarisation angle, the charged lepton pT and rapidity, and the pT of the W boson from the top quark decay. In addition, the charge ratio is measured differentially as a function of the top quark, charged lepton, and W boson kinematic observables. The results are found to be in agreement with standard model predictions using various next-to-leading-order event generators and sets of parton distribution functions. Additionally, the spin asymmetry, sensitive to the top quark polarisation, is determined from the differential distribution of the polarisation angle at parton level to be 0.440 ± 0.070 , in agreement with the standard model prediction.