Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 3Citation - Scopus: 33Search for New Physics in Final States With a Single Photon and Missing Transverse Momentum in Proton-Proton Collisions at <mml:msqrt>s</Mml:msqrt>=13 Tev(Springer Verlag, 2019) Karapınar, Güler; CMS CollaborationA search is conducted for new physics in final states containing a photon and missing transverse momentum in proton-proton collisions at <mml:msqrt>s</mml:msqrt>=13 TeV, using the data collected in 2016 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb(-1). No deviations from the predictions of the standard model are observed. The results are interpreted in the context of dark matter production and models containing extra spatial dimensions, and limits on new physics parameters are calculated at 95% confidence level. For the two simplified dark matter production models considered, the observed (expected) lower limits on the mediator masses are both 950 (1150) GeV for 1 GeV dark matter mass. For an effective electroweak-dark matter contact interaction, the observed (expected) lower limit on the suppression parameter is 850 (950) GeV. Values of the effective Planck scale up to 2.85-2.90 TeV are excluded for between 3 and 6 extra spatial dimensions.Article Citation - WoS: 23Citation - Scopus: 42Search for Dark Matter Produced in Association With a Single Top Quark or a Top Quark Pair in Proton-Proton Collisions at S=13 Tev(Springer Verlag, 2019) Karapınar, Güler; CMS CollaborationA search for dark matter produced in association with top quarks in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. The data set used corresponds to an integrated luminosity of 35.9 fb(-1) recorded with the CMS detector at the LHC. Whereas previous searches for neutral scalar or pseudoscalar mediators considered dark matter production in association with a top quark pair only, this analysis also includes production modes with a single top quark. The results are derived from the combination of multiple selection categories that are defined to target either the single top quark or the top quark pair signature. No significant deviations with respect to the standard model predictions are observed. The results are interpreted in the context of a simplified model in which a scalar or pseudoscalar mediator particle couples to a top quark and subsequently decays into dark matter particles. Scalar and pseudoscalar mediator particles with masses below 290 and 300 GeV, respectively, are excluded at 95% confidence level, assuming a dark matter particle mass of 1 GeV and mediator couplings to fermions and dark matter particles equal to unity.Article Citation - WoS: 60Citation - Scopus: 78Search for Heavy Neutrinos and Third-Generation Leptoquarks in Hadronic States of Two Leptons and Two Jets in Proton-Proton Collisions at Root S=13 Tev(Springer Verlag, 2019) Karapınar, Güler; CMS CollaborationA search for new particles has been conducted using events with two high transverse momentum leptons that decay hadronically and at least two energetic jets. The analysis is performed using data from proton-proton collisions at 13 TeV, collected by the CMS experiment at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb(-1). The observed data are consistent with standard model expectations. The results are interpreted in the context of two physics models. The first model involves right-handed charged bosons, W-R, that decay to heavy right-handed Majorana neutrinos, N ( = e, , ), arising in a left-right symmetric extension of the standard model. The model considers that N-e and N are too heavy to be detected at the LHC. Assuming that the N mass is half of the W-R mass, masses of the W-R boson below 3.50 TeV are excluded at 95% confidence level. Exclusion limits are also presented considering different scenarios for the mass ratio between N and W-R, as a function of W-R mass. In the second model, pair production of third-generation scalar leptoquarks that decay into bb is considered, resulting in an observed exclusion region with leptoquark masses below 1.02 TeV, assuming a 100% branching fraction for the leptoquark decay to a lepton and a bottom quark. These results represent the most stringent limits to date on these models.Article Citation - WoS: 30Citation - Scopus: 38Search for Dark Matter Particles Produced in Association With a Higgs Boson in Proton-Proton Collisions at Root S=13tev(Springer Verlag, 2020) Karapınar, Güler; CMS CollaborationA search for dark matter (DM) particles is performed using events with a Higgs boson candidate and large missing transverse momentum. The analysis is based on proton- proton collision data at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb(-1). The search is performed in five Higgs boson decay channels: h -> b (b) over bar, gamma gamma, tau(+)tau(-), W+W-, and ZZ. The results from the individual channels are combined to maximize the sensitivity of the analysis. No significant excess over the expected standard model background is observed in any of the five channels or in their combination. Limits are set on DM production in the context of two simplified models. The results are also interpreted in terms of a spin-independent DM-nucleon scattering cross section and compared to those from direct-detection DM experiments. This is the first search for DM particles produced in association with a Higgs boson decaying to a pair of W or Z bosons, and the first statistical combination based on five Higgs boson decay channels.Article Citation - WoS: 10Citation - Scopus: 33Search for Dark Matter Produced in Association With a Higgs Boson Decaying To ?? or ? + ? - at ?s=13 Tev(Springer Verlag, 2018) CMS Collaboration; Karapınar, GülerA search for dark matter particles is performed by looking for events with large transverse momentum imbalance and a recoiling Higgs boson decaying to either a pair of photons or a pair of τ leptons. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV collected at the CERN LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb−1. No significant excess over the expected standard model background is observed. Upper limits at 95% confidence level are presented for the product of the production cross section and branching fraction in the context of two benchmark simplified models. For the Z′-two-Higgs-doublet model (where Z′ is a new massive boson mediator) with an intermediate heavy pseudoscalar particle of mass mA = 300 GeV and mDM = 100 GeV, the Z′ masses from 550 GeV to 1265 GeV are excluded. For a baryonic Z′ model, with mDM = 1 GeV, Z′ masses up to 615 GeV are excluded. Results are also presented for the spin-independent cross section for the dark matter-nucleon interaction as a function of the mass of the dark matter particle. This is the first search for dark matter particles produced in association with a Higgs boson decaying to two τ leptonsArticle Citation - WoS: 21Citation - Scopus: 41Search for Dark Matter in Events With Energetic, Hadronically Decaying Top Quarks and Missing Transverse Momentum at ?s=13 Tev(Springer Verlag, 2018) CMS Collaboration; Karapınar, GülerA search for dark matter is conducted in events with large missing transverse momentum and a hadronically decaying, Lorentz-boosted top quark. This study is performed using proton-proton collisions at a center-of-mass energy of 13 TeV, in data recorded by the CMS detector in 2016 at the LHC, corresponding to an integrated luminosity of 36 fb−1. New substructure techniques, including the novel use of energy correlation functions, are utilized to identify the decay products of the top quark. With no significant deviations observed from predictions of the standard model, limits are placed on the production of new heavy bosons coupling to dark matter particles. For a scenario with purely vector-like or purely axial-vector-like flavor changing neutral currents, mediator masses between 0.20 and 1.75 TeV are excluded at 95% confidence level, given a sufficiently small dark matter mass. Scalar resonances decaying into a top quark and a dark matter fermion are excluded for masses below 3.4 TeV, assuming a dark matter mass of 100 GeV.Article Citation - WoS: 42Citation - Scopus: 83Search for Low Mass Vector Resonances Decaying Into Quark-Antiquark Pairs in Proton-Proton Collisions at √s=13 Tev(Springer Verlag, 2018) CMS Collaboration; Karapınar, GülerA search for narrow vector resonances decaying into quark-antiquark pairs is presented. The analysis is based on data collected in proton-proton collisions at s=13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb −1 . The hypothetical resonance is produced with sufficiently high transverse momentum that its decay products are merged into a single jet with two-prong substructure. A signal would be identified as a peak over a smoothly falling background in the distribution of the invariant mass of the jet, using novel jet substructure techniques. No evidence for such a resonance is observed within the mass range of 50-300 GeV. Upper limits at 95% confidence level are set on the production cross section, and presented in a mass-coupling parameter space. The limits further constrain simplified models of dark matter production involving a mediator interacting between quarks and dark matter particles through a vector or axial-vector current. In the framework of these models, the results are the most sensitive to date, extending for the first time the search region to masses below 100 GeV.[Figure not available: see fulltext.].Article Citation - WoS: 16Citation - Scopus: 44Search for New Physics in the Monophoton Final State in Proton-Proton Collisions at ?s=13 Tev(Springer Verlag, 2017) CMS Collaboration; Karapınar, GülerA search is conducted for new physics in a final state containing a photon and missing transverse momentum in proton-proton collisions at s=13 TeV. The data collected by the CMS experiment at the CERN LHC correspond to an integrated luminosity of 12.9 fb−1. No deviations are observed relative to the predictions of the standard model. The results are interpreted as exclusion limits on the dark matter production cross sections and parameters in models containing extra spatial dimensions. Improved limits are set with respect to previous searches using the monophoton final state. In particular, the limits on the extra dimension model parameters are the most stringent to date in this channelArticle Citation - WoS: 25Citation - Scopus: 30Search for Associated Production of Dark Matter With a Higgs Boson Decaying To B B ¯ or ?? at ?s=13 Tev(Springer Verlag, 2017) CMS Collaboration; Karapınar, GülerA search for dark matter is performed looking for events with large missing transverse momentum and a Higgs boson decaying either to a pair of bottom quarks or to a pair of photons. The data from proton-proton collisions at a center-of-mass energy of 13 TeV, collected in 2015 with the CMS detector at the LHC, correspond to an integrated luminosity of 2.3 fb−1. Results are interpreted in the context of a Z′-two-Higgs-doublet model, where the gauge symmetry of the standard model is extended by a U(1)Z ′ group, with a new massive Z′ gauge boson, and the Higgs sector is extended with four additional Higgs bosons. In this model, a high-mass resonance Z′ decays into a pseudoscalar boson A and a light SM-like scalar Higgs boson, and the A decays to a pair of dark matter particles. No significant excesses are observed over the background prediction. Combining results from the two decay channels yields exclusion limits in the signal cross section in the mZ ′ - mA phase space. For example, the observed data exclude the Z′ mass range from 600 to 1860 GeV, for Z′ coupling strength gZ ′ = 0.8, the coupling of A with dark matter particles gχ = 1, the ratio of the vacuum expectation values tan β = 1, and mA = 300 GeV. The results of this analysis are valid for any dark matter particle mass below 100 GeV.Article Citation - WoS: 4Citation - Scopus: 4Hidden Spin-3/2 Field in the Standard Model(Springer Verlag, 2017) Demir, Durmuş Ali; Karahan, Canan; Korutlu, Beste; Sargın, OzanHere we show that a massive spin-3/2 field can hide in the SM spectrum in a way revealing itself only virtually. We study collider signatures and loop effects of this field, and determine its role in Higgs inflation and its potential as dark matter. We show that this spin-3/2 field has a rich linear collider phenomenology and motivates consideration of a neutrino–Higgs collider. We also show that the study of Higgs inflation, dark matter and dark energy can reveal more about the neutrino and dark sector. © 2017, The Author(s).