Natural and Mathematical Sciences

Permanent URI for this collectionhttps://hdl.handle.net/10679/313

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Now showing 1 - 20 of 396

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Alignment of the CMS tracker with LHC and cosmic ray data
(IOP Publishing, 2014-06) Chatrchyan, S.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
Results are reported from a search for supersymmetry in pp collisions at a center-of-mass energy of 8 TeV, based on events with a single isolated lepton (electron or muon) and multiple jets, at least two of which are identified as b jets. The data sample corresponds to an integrated luminosity of 19.3 fb(-1) recorded by the CMS experiment at the LHC in 2012. The search is motivated by supersymmetric models that involve strong-production processes and cascade decays of new particles. The resulting final states contain multiple jets as well as missing transverse momentum from weakly interacting particles. The event yields, observed across several kinematic regions, are consistent with the expectations from standard model processes. The results are interpreted in the context of simplified supersymmetric scenarios with pair production of gluinos, where each gluino decays to a top quark-antiquark pair and the lightest neutralino. For the case of decays via virtual top squarks, gluinos with a mass smaller than 1.26 TeV are excluded for low neutralino masses
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Angular analysis and branching fraction measurement of the decay B-0 -> K*(0)mu(+)mu(-)
(Elsevier, 2013-11-25) Chatrchyan, S.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The angular distributions and the differential branching fraction of the decay B0→K⁎(892)0μ+μ− are studied using a data sample corresponding to an integrated luminosity of 5.2 fb−1 collected with the CMS detector at the LHC in pp collisions at View the MathML source. From more than 400 signal decays, the forward–backward asymmetry of the muons, the K⁎(892)0 longitudinal polarization fraction, and the differential branching fraction are determined as a function of the square of the dimuon invariant mass. The measurements are in good agreement with standard model predictions.
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Approximate markov-nash equilibria for discrete-time risk-sensitive mean-field games
(Informs, 2020-11) Saldı, Naci; Basar, T.; Raginsky, M.; Natural and Mathematical Sciences; SALDI, Naci
In this paper, we study a class of discrete-time mean-field games under the infinite-horizon risk-sensitive optimality criterion. Risk sensitivity is introduced for each agent (player) via an exponential utility function. In this game model, each agent is coupled with the rest of the population through the empirical distribution of the states, which affects both the agent's individual cost and its state dynamics. Under mild assumptions, we establish the existence of a mean-field equilibrium in the infinite-population limit as the number of agents (N) goes to infinity, and we then show that the policy obtained from the mean-field equilibrium constitutes an approximate Nash equilibrium when N is sufficiently large.
Open Access
B → T transition form factors in light-cone sum rules
(American Physical Society, 2019-11-11) Aliev, T. M.; Dağ, Hüseyin; Kokulu, A.; Ozpineci, A.; Natural and Mathematical Sciences; DAĞ, Hüseyin
We present a new calculation of the semileptonic tree-level and flavor-changing neutral current form factors describing B-meson transitions to tensor mesons T ¼ D2, K2, a2, f2 (JP ¼ 2þ). We employ the QCD light-cone sum rules approach with B-meson distribution amplitudes. We go beyond the leading-twist accuracy and provide analytically, for the first time, higher-twist corrections for the two-particle contributions up to twist-four terms. We observe that the impact of higher-twist terms to the sum rules is noticeable. We study the phenomenological implications of our results on the radiative B → K 2γ and semileptonic B → D 2lν¯l, B → K 2lþl− decays.
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Biocompatible MOFs for storage and separation of O2: A molecular simulation study
(American Chemical Society, 2019-02-27) Gülçay, Ezgi; Fındıkçı, İlknur Eruçar; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar; Gülçay, Ezgi
Metal organic frameworks (MOFs) are great candidates for capturing 02 due to their highly porous structures and tunable physical and chemical properties. In this study, we assessed the performance of 1525 biocompatible MOFs which have endogenous linkers and nontoxic metal centers for adsorption-based and membrane-based O-2 separation and also for high-pressure O-2 storage. We initially computed Henry's constants of O-2 and N-2 at zero coverage and 298 K by performing Grand Canonical Monte Carlo (GCMC) simulations and estimated infinite dilution adsorption selectivities for O-2/N-2 mixture. We performed binary mixture GCMC simulations for the top 15 candidates at various pressures and 298 K and compared mixture adsorption selectivities with those obtained from infinite dilution. We then estimated O-2 working capacities of 315 biocompatible MOFs obtained at 298 K and 140 bar for storage and 5 bar for release pressures. Our results showed that 15 biocompatible MOFs outperform gravimetric O-2 working capacities of the traditional adsorbent materials such as activated carbon and NaX and some common MOFs such as NU-125 and UMCM-152 at 298 K. We finally calculated O-2 and N-2 permeabilities and membrane selectivities of 45 promising MOF candidates for O-2/N-2 separation. Seventeen biocompatible MOF membranes were identified to exceed the Robeson's upper bound established for polymers. This computational study will be useful to identify the promising biocompatible MOFs for storage and separation of O-2. The bio-MOF library constructed in this study will also guide both experimental and computational studies for design and development of biocompatible MOFs for various medical applications.
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Charged-particle nuclear modification factors in PbPb and pPb collisions at root s(NN)=5.02 TeV
(Springer International Publishing, 2017) Khachatryan, V.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The spectra of charged particles produced within the pseudorapidity window |η| < 1 at sNN−−−−√=5.02sNN=5.02 TeV are measured using 404 μb−1 of PbPb and 27.4 pb−1 of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0.5 < pT< 400 GeV in pp and 0.7 < pT< 400 GeV in PbPb collisions. The corresponding nuclear modification factor, RAA, is measured in bins of collision centrality. The RAA in the 5% most central collisions shows a maximal suppression by a factor of 7-8 in the pT region of 6-9 GeV. This dip is followed by an increase, which continues up to the highest pT measured, and approaches unity in the vicinity of pT = 200 GeV. The RAA is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear modification factor, RpA, up to 120 GeV. For pT> 20 GeV, RpA exhibits weak momentum dependence and shows a moderate enhancement above unity.
Open Access
Charmed baryon spectrum from lattice QCD near the physical point
(American Physical Society, 2020-09-23) Bahtiyar, H.; Can, K. U.; Erkol, Güray; Gubler, P.; Oka, M.; Takahashi, T. T.; TRJQCD Collaboration; Natural and Mathematical Sciences; ERKOL, Güray
We calculate the low-lying spectrum of charmed baryons in lattice QCD on the 32(3) x 64, N-f = 2 +/- 1 PACS-CS gauge configurations at the almost physical pion mass of similar to 156 MeV/c(2). By employing a set of interpolating operators with different Dirac structures and quark-field smearings for the variational analysis, we extract the ground and first few excited states of the spin-1/2 and spin-3/2, singly, doubly, and triply charmed baryons. Additionally, we study the Xi(c)-Xi(c)' mixing and the operator dependence of the excited states in a variational approach. We identify several states that lie close to the experimentally observed excited states of the Sigma(c), Xi(c) and Omega(c) baryons, including some of the Xi(c) states recently reported by LHCb. Our results for the doubly and triply charmed baryons are suggestive for future experiments.
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Choquet-Monge-Ampère classes
(Springer Nature, 2017) Guedj, V.; Şahin, Sibel; Zeriahi, A.; Natural and Mathematical Sciences; ŞAHİN, Sibel
We introduce and study Choquet-Monge-Ampère classes on compact Kähler manifolds. They consist of quasi-plurisubharmonic functions whose sublevel sets have small enough asymptotic Monge-Ampère capacity. We compare them with finite energy classes, which have recently played an important role in Kähler Geometry.
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Combined measurement of the Higgs boson mass in pp collisions at root s=7 and 8 TeV with the ATLAS and CMS experiments
(American Physical Society, 2015-05-15) Aad, G.; Işıldak, Bora; The ATLAS Collaboration; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4ℓ decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is mH=125.09±0.21 (stat)±0.11 (syst) GeV.
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Combined search for anomalous pseudoscalar HVV couplings in VH(H→bb‾) production and H → VV decay
(Elsevier, 2016-08-10) Khachatryan, V.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
A search for anomalous pseudoscalar couplings of the Higgs boson H to electroweak vector bosons V (=W or Z) in a sample of proton–proton collision events corresponding to an integrated luminosity of 18.9 fb−1 at a center-of-mass energy of 8 TeV is presented. Events consistent with the topology of associated VH production, where the Higgs boson decays to a pair of bottom quarks and the vector boson decays leptonically, are analyzed. The consistency of data with a potential pseudoscalar contribution to the HVV interaction, expressed by the effective pseudoscalar cross section fractions fa3, is assessed by means of profile likelihood scans. Results are given for the VH channels alone and for a combined analysis of the VH and previously published H→VV channels. Under certain assumptions, View the MathML source is excluded at 95% confidence level in the combination. Scenarios in which these assumptions are relaxed are also considered.
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Combined search for the quarks of a sequential fourth generation
(American Physical Society, 2012-12-01) Chatrchyan, S.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 fb(-1) recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.
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Comparison of the Z/γ ∗ + jets to γ + jets cross sections in pp collisions at = 8 TeV
(Springer International Publishing, 2015-10) Khachatryan, V.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
A comparison of the differential cross sections for the processes Z/γ * + jets and photon (γ)+jets is presented. The measurements are based on data collected with the CMS detector at s√=8s=8 TeV corresponding to an integrated luminosity of 19.7 fb−1. The differential cross sections and their ratios are presented as functions of p T. The measurements are also shown as functions of the jet multiplicity. Differential cross sections are obtained as functions of the ratio of the Z/γ * p T to the sum of all jet transverse momenta and of the ratio of the Z/γ * p T to the leading jet transverse momentum. The data are corrected for detector effects and are compared to simulations based on several QCD calculations.
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Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs
(Elsevier, 2014-07-09) Chatrchyan, S.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
Constraints are presented on the total width of the recently discovered Higgs boson, Gamma(H), using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1 fb(-1) at a center-of-mass energy root s = 7 TeV and 19.7 fb(-1) at root s = 8 TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of Gamma(H) < 22 MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of m(H) = 125.6 GeV.
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Determination of the top-quark pole mass and strong coupling constant from the tt production cross section in pp collisions at root s=7 TeV
(Elsevier, 2014-01-20) Chatrchyan, S.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The inclusive cross section for top-quark pair production measured by the CMS experiment in proton–proton collisions at a center-of-mass energy of 7 TeV is compared to the QCD prediction at next-to-next-to-leading order with various parton distribution functions to determine the top-quark pole mass, View the MathML source, or the strong coupling constant, αS. With the parton distribution function set NNPDF2.3, a pole mass of View the MathML source is obtained when constraining αS at the scale of the Z boson mass, mZ, to the current world average. Alternatively, by constraining View the MathML source to the latest average from direct mass measurements, a value of View the MathML source is extracted. This is the first determination of αS using events from top-quark production.
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Differential cross section measurements for the production of a W boson in association with jets in proton-proton collisions at s = 7 TeV
(Elsevier, 2015-02-04) Khachatryan, V.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb−1. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.
Open Access
Discrete-time average-cost mean-field games on Polish spaces
(TÜBİTAK, 2020) Saldı, Naci; Natural and Mathematical Sciences; SALDI, Naci
In stochastic dynamic games, when the number of players is sufficiently large and the interactions between agents depend on empirical state distribution, one way to approximate the original game is to introduce infinite-population limit of the problem. In the infinite population limit, a generic agent is faced with a so-called mean-field game. In this paper, we study discrete-time mean-field games with average-cost criteria. Using average cost optimality equation and Kakutani's fixed point theorem, we establish the existence of Nash equilibria for mean-field games under drift and minorization conditions on the dynamics of each agent. Then, we show that the equilibrium policy in the mean-field game, when adopted by each agent, is an approximate Nash equilibrium for the corresponding finite-agent game with sufficiently many agents.
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Electromagnetic properties of doubly charmed baryons in Lattice QCD
(Elsevier, 2013-11-04) Can, K. Utku; Erkol, Güray; Işıldak, Bora; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray; IŞILDAK, Bora; Can, K. Utku
We compute the electromagnetic properties of Ξcc baryons in (2+1)-flavor Lattice QCD. By measuring the electric charge and magnetic form factors of Ξcc baryons, we extract the magnetic moments, charge and magnetic radii as well as the ΞccΞccρ coupling constant, which provide important information to understand the size, shape and couplings of the doubly charmed baryons. We find that the two heavy charm quarks drive the charge radii and the magnetic moment of Ξcc to smaller values as compared to those of, e.g., the proton.
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Electromagnetic structure of charmed baryons in Lattice QCD
(Springer Science+Business Media, 2014-05) Can, Kadir Utku; Erkol, Güray; Işıldak, Bora; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray; IŞILDAK, Bora; Can, Kadir Utku
As a continuation of our recent work on the electromagnetic properties of the doubly charmed (sic)(cc) baryon, we compute the charge radii and the magnetic moments of the singly charmed Sigma(c), Omega(c) and the doubly charmed Omega(cc) baryons in 2+1 flavor Lattice QCD. In general, the charmed baryons are found to be compact as compared to the proton. The charm quark acts to decrease the size of the baryons to smaller values. We discuss the mechanism behind the dependence of the charge radii on the light valence- and sea-quark masses. The magnetic moments are found to be almost stable with respect to changing quark mass. We investigate the individual quark sector contributions to the charge radii and the magnetic moments. The magnetic moments of the singly charmed baryons are found to be dominantly determined by the light quark and the role of the charm quark is significantly enhanced for the doubly charmed baryons.
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Electromagnetic structure of charmed hadrons
(IOP Publishing, 2014) Erkol, Güray; Can, K. U.; Işıldak, Bora; Oka, M.; Ozpineci, A.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray; IŞILDAK, Bora
We compute the electromagnetic structures of D and D* mesons, the singly charmed Σc, Ωc and the doubly charmed Ξcc, Ωcc baryons in 2+1 flavor Lattice QCD. We extract the charge radii and the magnetic moments of these hadrons. In general, charmed hadrons are found to be more compact as compared to light hadrons. The magnetic moments of the singly charmed baryons are found to be dominantly determined by the light quark and the role of the charm quark is significantly enhanced when it is doubly represented.
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Energy calibration and resolution of the CMS electromagnetic calorimeter in pp collisions at √s = 7 TeV
(2013-09) Chatrchyan, S.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The energy calibration and resolution of the electromagnetic calorimeter (ECAL) of the CMS detector have been determined using proton-proton collision data from LHC operation in 2010 and 2011 at a centre-of-mass energy of √s = 7 TeV with integrated luminosities of about 5\fbinv. Crucial aspects of detector operation, such as the environmental stability, alignment, and synchronization, are presented. The in-situ calibration procedures are discussed in detail and include the maintenance of the calibration in the challenging radiation environment inside the CMS detector. The energy resolution for electrons from Z-boson decays is better than 2% in the central region of the ECAL barrel (for pseudorapidity |η| < 0.8) and is 2–5% elsewhere. The derived energy resolution for photons from 125 GeV Higgs boson decays varies across the barrel from 1.1% to 2.6% and from 2.2% to 5% in the endcaps. The calibration of the absolute energy is determined from Z→e+e− decays to a precision of 0.4% in the barrel and 0.8% in the endcaps.

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