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Öğe Search for light long-lived particles decaying to displaced jets in proton-proton collisions at √s = 13.6 tev(Institute of Physics, 2025) Hayrapetyan A.; Sağır, Sinan; CMS CollaborationA search for light long-lived particles (LLPs) decaying to displaced jets is presented, using a data sample of proton-proton collisions at a center-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 34.7 fb−1, collected with the CMS detector at the CERN LHC in 2022. Novel trigger, reconstruction, and machine-learning techniques were developed for and employed in this search. After all selections, the observations are consistent with the background predictions. Limits are presented on the branching fraction of the Higgs boson to LLPs that subsequently decay to quark pairs or tau lepton pairs. An improvement by up to a factor of 10 is achieved over previous limits for models with LLP masses smaller than 60 GeV and proper decay lengths smaller than 1 m. The first constraints are placed on the fraternal twin Higgs (FTH) and folded supersymmetry (FSUSY) models, where the lower bounds on the top quark partner mass reach up to 350 GeV for the FTH model and 250 GeV for the FSUSY model. © 2025 The Author(s). Published by IOP Publishing Ltd.Öğe Search for charged-lepton flavor violation in the production and decay of top quarks using trilepton final states in proton-proton collisions at (Formula presented)(American Physical Society, 2025) Hayrapetyan. A.; Sağır,SinanA search is performed for charged-lepton flavor violating processes in top quark ((Formula presented)) production and decay. The data were collected by the CMS experiment from proton-proton collisions at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of (Formula presented). The selected events are required to contain one opposite-sign electron-muon pair, a third charged lepton (electron or muon), and at least one jet of which no more than one is associated with a bottom quark. Boosted decision trees are used to distinguish signal from background, exploiting differences in the kinematics of the final states particles. The data are consistent with the standard model expectation. Upper limits at 95% confidence level are placed in the context of effective field theory on the Wilson coefficients, which range between (Formula presented) depending on the flavor of the associated light quark and the Lorentz structure of the interaction. These limits are converted to upper limits on branching fractions involving up (charm) quarks, (Formula presented) ((Formula presented)), of (Formula presented), (Formula presented), and (Formula presented) for tensorlike, vectorlike, and scalarlike interactions, respectively. © 2025 CERN, for the CMS Collaboration.Öğe Measurement of inclusive and differential cross sections for w+w- production in proton-proton collisions at √s=13.6 tev(2025) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W; Bergauer, T.; Chatterjee, S.; Sağır, SinanMeasurements at root s = 13.6 TeV of the opposite-sign W boson pair production cross section in proton-proton collisions are presented. The data used in this study were collected with the CMS detector at the CERN LHC in 2022, and correspond to an integrated luminosity of 34.8 fb(-1). Events are selected by requiring one electron and one muon of opposite charge. A maximum likelihood fit is performed on signal- and background-enriched data categories dfined by the flavor and charge of the leptons, the number of jets, and number of jets originating from b quarks. The overall sensitivity is significantly better than that of previous results with a similar integrated luminosity. The improvement comes from a more rfined control of experimental uncertainties and an improved fit strategy. An inclusive W+W- production cross section of 125.7 +/- 5.6 pb is measured, in agreement with standard model predictions. Cross sections are also reported in a fiducial region close to that of the detector acceptance, both inclusively and differentially, as a function of the jet multiplicity in the event. For the first time in proton-proton collisions, WWevents with zero, one, and at least two jets are studied simultaneously and compared with recent theoretical predictions.Öğe Search for central exclusive production of top quark pairs in proton-proton collisions at √s=13 tev with tagged protons(Springer, 2025) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Sağır, SinanA search for the central exclusive production of top quark-antiquark pairs (t (t) over bar) is performed for the first time using proton-tagged events in proton-proton collisions at the LHC at a centre-of-mass energy of 13TeV. The data correspond to an integrated luminosity of 29.4 fb(-1). The t (t) over bar decay products are reconstructed using the central CMS detector, while forward protons are measured in the CMS-TOTEM precision proton spectrometer. An observed (expected) upper bound on the production cross section of 0.59 (1.14) pb is set at 95% confidence level, for collisions of protons with fractional momentum losses between 2 and 20%.Öğe Search for a standard model-like Higgs boson in the mass range between 70 and 110 GeV in the diphoton final state in proton-proton collisions at √s=13 TeV(Elsevier, 2025) Hayrapetyan, A.; Sağır, SinanThe results of a search for a standard model-like Higgs boson decaying into two photons in the mass range between 70 and 110 GeV are presented. The analysis uses the data set collected by the CMS experiment in proton-proton collisions at root s = 13 TeV corresponding to integrated luminosities of 36.3 fb(-1), 41.5 fb(-1) and 54.4 fb(-1) during the 2016, 2017, and 2018 LHC running periods, respectively. No significant excess over the background expectation is observed and 95% cofidence level upper limits are set on the product of the cross section and branching fraction for decays of an additional Higgs boson into two photons. The maximum deviation with respect to the background is seen for a mass hypothesis of 95.4 GeV with a local (global) significance of 2.9 (1.3) standard deviations. The observed upper limit ranges from 15 to 73 fb.Öğe Measurement of boosted Higgs bosons produced via vector boson fusion or gluon fusion in the H → b(b)over-bar decay mode using LHC proton-proton collision data at √s=13 TeV(Springer, 2024) Hayrapetyan, A.; Sağır, SinanA measurement is performed of Higgs bosons produced with high transverse momentum (p(T)) via vector boson or gluon fusion in proton-proton collisions. The result is based on a data set with a center-of-mass energy of 13 TeV collected in 2016-2018 with the CMS detector at the LHC and corresponds to an integrated luminosity of 138 fb(-1). The decay of a high-p(T) Higgs boson to a boosted bottom quark-antiquark pair is selected using large-radius jets and employing jet substructure and heavy-flavor taggers based on machine learning techniques. Independent regions targeting the vector boson and gluon fusion mechanisms are defined based on the topology of two quark-initiated jets with large pseudorapidity separation. The signal strengths for both processes are extracted simultaneously by performing a maximum likelihood fit to data in the large-radius jet mass distribution. The observed signal strengths relative to the standard model expectation are 4.9(-1.6)(+1.9) and 1.6(-1.5)(+1.7) for the vector boson and gluon fusion mechanisms, respectively. A differential cross section measurement is also reported in the simplified template cross section framework.Öğe Search for Higgs boson pair production in the b(b)over-bar W+W- decay mode in proton-proton collisions at √s=13 TeV(Springer, 2024) Hayrapetyan, A.; Sağır, SinanA search for Higgs boson pair (HH) production with one Higgs boson decaying to two bottom quarks and the other to two W bosons are presented. The search is done using proton-proton collisions data at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 138 fb(-1) recorded by the CMS detector at the LHC from 2016 to 2018. The final states considered include at least one leptonically decaying W boson. No evidence for the presence of a signal is observed and corresponding upper limits on the HH production cross section are derived. The limit on the inclusive cross section of the nonresonant HH production, assuming that the distributions of kinematic observables are as expected in the standard model (SM), is observed (expected) to be 14 (18) times the value predicted by the SM, at 95% confidence level. The limits on the cross section are also presented as functions of various Higgs boson coupling modifiers, and anomalous Higgs boson coupling scenarios. In addition, limits are set on the resonant HH production via spin-0 and spin-2 resonances within the mass range 250-900 GeV.Öğe Search for bottom quark associated production of the standard model Higgs boson in final states with leptons in proton-proton collisions at √s=13 TeV(2024) Hayrapetyan, A.; Sağır, SinanThis Letter presents the first search for bottom quark associated production of the standard model Higgs boson, in final states with leptons. Higgs boson decays to pairs of tau leptons and pairs of leptonically decaying W bosons are considered. The search is performed using data collected from 2016 to 2018 by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb(-1). Upper limits at the 95% confidence level are placed on the signal strength for Higgs boson production in association with bottom quarks; the observed (expected) upper limit is 3.7 (6.1) times the standard model prediction.Öğe Measurement of the production cross section of a Higgs boson with large transverse momentum in its decays to a pair of τ leptons in proton-proton collisions at √s=13 TeV(2024) Hayrapetyan, A.; Sağır, SinanA measurement of the production cross section of a Higgs boson with transverse momentum greater than 250 GeV is presented where the Higgs boson decays to a pair of tau leptons. It is based on proton-proton collision data collected by the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb(-1). Because of the large transverse momentum of the Higgs boson the tau leptons from its decays are boosted and produced spatially close, with their decay products overlapping. Therefore, a dedicated algorithm was developed to reconstruct and identify them. The observed (expected) significance of the measured signal with respect to the standard model background-only hypothesis is 3.5 (2.2) standard deviations. The product of the production cross section and branching fraction is measured to be 1.64(-0.54)(+0.68) times the standard model expectation. The fiducial differential production cross section is also measured as functions of the Higgs boson and leading jet transverse momenta. This measurement extends the probed large-transverse-momentum region in the tau tau final state beyond 600 GeV.Öğe Observation of quantum entanglement in top quark pair production in proton-proton collisions at √s=13 TeV(2024) Hayrapetyan, A.; Sağır, SinanEntanglement is an intrinsic property of quantum mechanics and is predicted to be exhibited in the particles produced at the Large Hadron Collider. A measurement of the extent of entanglement in top quark-antiquark (t (t) over bar) events produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed with the data recorded by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 36.3 fb(-1). The events are selected based on the presence of two leptons with opposite charges and high transverse momentum. An entanglement-sensitive observable D is derived from the top quark spin-dependent parts of the t (t) over bar production density matrix and measured in the region of the t (t) over bar production threshold. Values of D < -1/3 are evidence of entanglement and D is observed (expected) to be -0.480(-0.029)(+0.026) (-0.467(-0.029)(+0.026)) at the parton level. With an observed significance of 5.1 standard deviations with respect to the non-entangled hypothesis, this provides observation of quantum mechanical entanglement within t (t) over bar pairs in this phase space. This measurement provides a new probe of quantum mechanics at the highest energies ever produced.Öğe Measurements of polarization and spin correlation and observation of entanglement in top quark pairs using (Formula presented) events from proton-proton collisions at (Formula presented)(American Physical Society, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Bergauer, T.; Chatterjee, S.; Sağır,SinanMeasurements of the polarization and spin correlation in top quark pairs ((Formula presented)) are presented using events with a single electron or muon and jets in the final state. The measurements are based on proton-proton collision data from the LHC at (Formula presented) collected by the CMS experiment, corresponding to an integrated luminosity of (Formula presented). All coefficients of the polarization vectors and the spin correlation matrix are extracted simultaneously by performing a binned likelihood fit to the data. The measurement is performed inclusively and in bins of additional observables, such as the mass of the (Formula presented) system and the top quark scattering angle in the (Formula presented) rest frame. The measured polarization and spin correlation are in agreement with the standard model. From the measured spin correlation, conclusions on the (Formula presented) spin entanglement are drawn by applying the Peres-Horodecki criterion. The standard model predicts entangled spins for (Formula presented) states at the production threshold and at high masses of the (Formula presented) system. Entanglement is observed for the first time in events at high (Formula presented) mass, where a large fraction of the (Formula presented) decays are spacelike separated, with an expected and observed significance of above 5 standard deviations. © 2024 CERN, for the CMS Collaboration.Öğe Quality of Life of Children Between 5 and 7 Years and Affecting Factors(Istanbul Univ, 2023) Dağtekin, Halime; Şahiner, Nejla CanbulatAim: This study has been carried out as a descriptive research in order to determine children's quality of life and the factors affecting their quality of life. Methods: The research data were obtained from 260 children between the ages of five and seven years and their parents in T & uuml;rkiye's Karaman province between September 2019-June 2020. Data were collected using a questionnaire form and the child and parent forms for the Quality of Life Scale for Children. The study used frequencies, percentages, means, min and max values, Cronbach's alphas, t test results, ANOVA testing, the Mann Whitney U-test, and regression analyses to analyze the data, with the Bonferonni correction test being used in further analyses. Results: Of the students examined within the scope of the study, 53.1% were determined to be girls and 50% to be six years old; their mean body mass index (BMI) was identified as 15.31 (SD = 2.61). The mean score from the child version of the Quality of Life Scale for Children was seen to be 71.23 (SD = 13.28), and the mean score from the parent version was seen to be 65.69 (SD = 14.11). The children's quality of life was determined to be affected by family income status, parents' educational status, the presence of chronic diseases in the parents, and the presence of any disease diagnosed in the child. Conclusion: According to the research results, the children were found to have high mean scores for their overall quality of life, while the children's quality of life scores as evaluated by the parents were found to be at a medium level. The lowest mean for the children's and parents' forms were found to occur in the sub-dimension of emotional functionality. The children's quality of life was observed to vary according to certain variables such as the family income level, parents' educational level, the presence of a chronic disease in the parents, and the presence of any disease diagnosed in the child.Öğe Nonresonant central exclusive production of charged-hadron pairs in proton-proton collisions at ?s=13 TeV(Amer Physical Soc, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Sağır, SinanThe central exclusive production of charged-hadron pairs in pp collisions at a center-of-mass energy of 13 TeV is examined, based on data collected in a special high-beta* run of the LHC. The nonresonant continuum processes are studied with the invariant mass of the centrally produced twopion system in the resonance-free region, m(pi+pi-) < 0.7 or m(pi+pi-) > 1.8 GeV. Differential cross sections as functions of the azimuthal angle between the surviving protons, squared exchanged four- momenta, and m(pi+pi-) are measured in a wide region of scattered proton transverse momenta, between 0.2 and 0.8 GeV, and for pion rapidities |y| < 2. A rich structure of interactions related to double-pomeron exchange is observed. A parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be interpreted as an effect of additional pomeron exchanges between the protons from the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities are determined that are related to the pomeron cross section, protonpomeron and meson-pomeron form factors, pomeron trajectory and intercept, and coefficients of diffractive eigenstates of the proton.Öğe Development of the CMS detector for the CERN LHC Run 3(Iop Publishing Ltd, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Arnold, B.; Bergauer, H.; Sağır, SinanSince the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger.Öğe Test of lepton flavor universality in B± ? K± ?+?- and B± ? K± e+ e- decays in proton-proton collisions at ?s=13 TeV(Iop Publishing Ltd, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.A test of lepton flavor universality in B-+/- -> K +/- mu(+) mu(-) and B-+/- -> (K)+/- e(+) e(-) decays, as well as a measurement of differential and integrated branching fractions of a nonresonant B-+/- -> K-+/- mu(+)mu(-) decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at root s = 13 TeV recorded in 2018, by the CMS experiment at the LHC, using a special high-rate data stream designed for collecting about 10 billion unbiased b hadron decays. The ratio of the branching fractions B(B-+/- -> K-+/- mu(+) mu(-)) to B(B-+/- -> K-+/- e(+) e(-)) is determined from the measured double ratio R(K) of these decays to the respective branching fractions of the B-+/- -> J/psi K-+/- with J/psi -> mu(+)mu(-) and e(+) e(-) decays, which allow for significant cancellation of systematic uncertainties. The ratio R(K) is measured in the range 1.1 < q(2) < 6.0 GeV2, where q is the invariant mass of the lepton pair, and is found to be R(K) = 0.78(-0.23)(+0.47), in agreement with the standard model expectation R(K) approximate to 1. This measurement is limited by the statistical precision of the electron channel. The integrated branching fraction in the same q(2) range, B(B-+/- -> K-+/- mu(+) mu(-)) = (12.42 +/- 0.68) x 10(-8), is consistent with the present world-average value and has a comparable precision.Öğe Extracting the speed of sound in quark-gluon plasma with ultrarelativistic lead-lead collisions at the LHC(Iop Publishing Ltd, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.Ultrarelativistic nuclear collisions create a strongly interacting state of hot and dense quark-gluon matter that exhibits a remarkable collective flow behavior with minimal viscous dissipation. To gain deeper insights into its intrinsic nature and fundamental degrees of freedom, we determine the speed of sound in an extended volume of quark-gluon plasma using lead-lead (PbPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data were recorded by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 0.607 nb(-1). The measurement is performed by studying the multiplicity dependence of the average transverse momentum of charged particles emitted in head-on PbPb collisions. Our findings reveal that the speed of sound in this matter is nearly half the speed of light, with a squared value of 0.241 +/- 0.002 (stat) +/- 0.016 9(syst) in natural units. The effective medium temperature, estimated using the mean transverse momentum, is 219 +/- 8 The measured squared speed of sound at this temperature aligns precisely with predictions from lattice quantum chromodynamic (QCD) calculations. This result provides a stringent constraint on the equation of state of the created medium and direct evidence for a deconfined QCD phase being attained in relativistic nuclear collisions.Öğe Research on Asylum-Seeking Preschool Children In Turkey: A Systematic Review(2024) Demirel, Özlem Yılmaz; Köroğlu, Alper Yusuf; Ataman, Safa Alparslan; Kösretaş, BarışThis study was conducted with the systematic review method to determine the studies conducted on children who are asylum-seekers in preschool period in Turkey and their results. Systematic reviews are important research projects that should be conducted by examining all studies conducted on a certain subject within a certain protocol. For this reason, the current study was carried out with the studies searched in Google Scholar and YÖKTEZ database by using the keywords \"asylum-seeking children\", \"asylum-seeking child\", \"refugee children\", \"refugee child\" without any date restriction in the research process. While the inclusion criteria for the systematic review were determined as studies conducted with children in the 0-6 age group, the exclusion criteria were determined as studies on children over the age of 6. Because of the keywords determined, a total of 2039 studies were reached and all of them were analyzed one by one. From these studies, 43 studies that were suitable for the study were identified. After removing duplicate studies, 29 studies that met the inclusion and exclusion criteria were included. When the studies were analyzed, it was seen that the problem of asylum-seekers is not limited to adults. Children are most affected by this situation.Öğe Measurement of multijet azimuthal correlations and determination of the strong coupling in proton-proton collisions at s=13TeV(Springer Nature, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Sağır, SinanA measurement is presented of a ratio observable that provides a measure of the azimuthal correlations among jets with large transverse momentum pT. This observable is measured in multijet events over the range of pT=360–3170GeV based on data collected by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 134fb-1. The results are compared with predictions from Monte Carlo parton-shower event generator simulations, as well as with fixed-order perturbative quantum chromodynamics (pQCD) predictions at next-to-leading-order (NLO) accuracy obtained with different parton distribution functions (PDFs) and corrected for nonperturbative and electroweak effects. Data and theory agree within uncertainties. From the comparison of the measured observable with the pQCD prediction obtained with the NNPDF3.1 NLO PDFs, the strong coupling at the Z boson mass scale is ?S(mZ)=0.1177±0.0013(exp)-0.0073 +0.0116(theo)=0.1177-0.0074 +0.0117, where the total uncertainty is dominated by the scale dependence of the fixed-order predictions. A test of the running of ?S in the TeV region shows no deviation from the expected NLO pQCD behaviour. © The Author(s) 2024.Öğe Search for Soft Unclustered Energy Patterns in Proton-Proton Collisions at 13 TeV(American Physical Society, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Sağır, SinanThe first search for soft unclustered energy patterns (SUEPs) is performed using an integrated luminosity of Formula Presented of proton-proton collision data at Formula Presented, collected in 2016-2018 by the CMS detector at the LHC. Such SUEPs are predicted by hidden valley models with a new, confining force with a large ’t Hooft coupling. In events with boosted topologies, selected by high-threshold hadronic triggers, the multiplicity and sphericity of clustered tracks are used to reject the background from standard model quantum chromodynamics. With no observed excess of events over the standard model expectation, limits are set on the cross section for production via gluon fusion of a scalar mediator with SUEP-like decays. © 2024 CERN, for the CMS Collaboration.Öğe Observation of Enhanced Long-Range Elliptic Anisotropies Inside High-Multiplicity Jets in pp Collisions at ?s = 13 TeV(American Physical Society, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Sağır, SinanA search for collective effects inside jets produced in proton-proton collisions is performed via correlation measurements of charged particles using the CMS detector at the CERN LHC. The analysis ffiffi uses data collected at a center-of-mass energy of ?s = 13 TeV, corresponding to an integrated luminosity of 138 fb?1. Jets are reconstructed with the anti-kT algorithm with a distance parameter of 0.8 and are required to have transverse momentum greater than 550 GeV and pseudorapidity (equation presented). Two-particle correlations among the charged particles within the jets are studied as functions of the particles' azimuthal angle and pseudorapidity separations (??* and ??*) in a jet coordinate basis, where particles' ?*, ?* are defined relative to the direction of the jet. The correlation functions are studied in classes of in-jet charged-particle multiplicity up to Njch ? 100. Fourier harmonics are extracted from long-range azimuthal correlation functions to characterize azimuthal anisotropy for (equation presented). For low-Njch jets, the long-range elliptic anisotropic harmonic, v*2, is observed to decrease with Njch. This trend is well described by Monte Carlo event generators. However, a rising trend for v*2 emerges at (equation presented), hinting at a possible onset of collective behavior, which is not reproduced by the models tested. This observation yields new insights into the dynamics of jet evolution in the vacuum. © 2024 CERN, for the CMS Collaboration.
