Yazar "Ocalan, Kadir" seçeneğine göre listele

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    Accurate prediction of the ??* distribution for the forward Z boson production in pp collisions through NNLO+N3LL
    (Korean Physical Soc, 2021) Ocalan, Kadir
    This paper presents a phenomenological study for the differential cross section of the forward Z boson production in leptonic decay channels as a function of the angular variable phi(eta)* in proton-proton collisions. The phi(eta)* distribution is predicted for the forward pseudorapidity region 2.0 <.. l < 4.5 of the decay leptons at center-of-mass energies of 8, 13, and 14 TeV. Accurate prediction of the phi(eta)* distribution is achieved by means of state-of-the-art calculations including fixed-order perturbative QCD and large logarithmic corrections. The predicted distributions are obtained by employing the resummation either at next-to-next-to-leading logarithmic (NNLL) or next-to- NNLL (N 3LL) accuracy which is matched to the perturbative QCD calculation at next- to-next-to-leading order ( NNLO) accuracy, that is at NNLO+NNLL and NNLO+N 3LL, respectively. The Z boson phi(eta)* variable is experimentally preferable as it has been measured more precisely than the Z boson transverse momentum, though both variables probe the same physics; therefore, an accurate description of the phi(eta)* variable is required using theoretical predictions at both NNLO+NNLL and NNLO+N-3 LL accuracies. The matched predictions are compared with the available 8-TeV and 13-TeV measurements by the LHCb experiment at the LHC and found to be in good agreement. The 14-TeV predicted distributions at both NNLO+NNLL and NNLO+N-3 LL are also reported. In all the predicted results, the NNLO+N-3 LL provides more improved accuracy for the reliable description of the phi(eta)* distribution throughout its entire phase space region.
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    Accurate prediction of the Drell-Yan ??* distribution in wide dilepton mass and rapidity ranges in pp collisions through NNLO+N3LL
    (Iop Publishing Ltd, 2021) Ocalan, Kadir
    This paper presents high-accuracy predictions for the differential cross ss as a function of the key observable phi(eta)* of the neutral-current Drell-Yan (DY) dilepton production in proton-proton (pp) collisions. The differential distributions for the phi(eta)* are presented by using the state-of-the-art predictions from the combined calculations of fixed-order perturbative quantum chromodynamics (QCD) corrections at next-to-next-to-leading order (NNLO) accuracy and resummation of large logarithmic terms at next-to-next-to-leading logarithmic (NNLL) and next-to-NNLL ((NLL)-L-3) accuracies, i.e., NNLO+NNLL and NNLO+(NLL)-L-3, respectively. The predicted distributions are reported for a thorough set of the DY dilepton invariant mass m(ll )ranges, spanning a wide kinematic region of 50 < m(ll ) < 1000 GeV both near and away from the Z-boson mass peak, and rapidity y(ll) ranges in the central detector acceptance region of vertical bar y(ll)vertical bar < 2.4. The differential phi(eta)* distributions in the wide m(ll) and y(ll) ranges offer stringent tests to assess the reliability of the predictions, where the m(ll )and y(ll) are closely correlated with the parton distribution functions (PDFs) of the incoming partons. The matched predictions through NNLO+(NLL)-L-3 are observed to provide good description of the 13 TeV pp collision data for the phi(eta)* (including the dilepton transverse momentum p(T)(ll) as well) distributions in almost the entire m(ll) and y(ll) ranges, apart from the intermediate- to high-phi(eta)* region in the lowest mass range 50-76 GeV which is assessed to constitute a challenge for the presented predictions. The predictions at NNLO+(NLL)-L-3 are also reported at 14 TeV for the upcoming high-luminosity running era of the Large Hadron Collider (LHC), in which increasing amount of data is expected to require more accurate and precise theoretical description. The most recent PDF models MSHT20 and CT18, in addition to the NNPDF3.1, are tested for the first time for the matched predictions of the phi(eta)* distribution. The differential distributions by the combined predictions through NNLO QCD+NLO EW are finally provided to enable assessment of the impact of the EW corrections for the phi(eta)*.
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    EW radiative corrections to theory predictions of charge asymmetry for W-boson hadroproduction
    (Iop Publishing Ltd, 2022) Ocalan, Kadir
    The higher-order predictions of the lepton charge asymmetry A eta l (the W-boson charge asymmetry A(yw)) for the leptonic final state of the W-boson hadroproduction in proton-proton (pp) collisions are presented. The predictions from the state-of-the-art computations are reported for achieving adequate description of the A(eta l) by including next-to-leading order (NLO) electroweak (EW) radiative corrections in combination with next-to-NLO (NNLO) quantum chromodynamics (QCD) radiative corrections. The combined predictions NNLO QCD+NLO EW and NNLO QCD x NLO EW, based on standard additive and factorised combination prescriptions in turn, are provided in the fiducial phase space of the pseudorapidity of the decay lepton (of the rapidity of the W-boson), comprising both central and forward detector acceptance regions as eta(l) <= 4.5 (y(W) <= 4.5). The inclusion of the NLO EW effects for the A(eta l) (A(yw)) constitutes additional input for the relative u- and d-quark densities in the proton, which is also of high importance in the domain of the high-precision studies. The predicted A(eta l) (A(yw)) distributions are compared with the actual measurements by CERN Large Hadron Collider (LHC) experiments at 8 TeV pp collisions energies. The combined predictions for the A(eta l) (A(yw)) distributions are also provided in comparisons with the NNLO QCD predictions at both 13 TeV and 14 TeV energies. The impact of the NLO EW corrections for the A(eta l) (A(yw)) distributions is extensively assessed by means of relative correction factor analysis with respect to the NNLO QCD predictions, in addition to a detailed K-factor analysis with respect to the leading order (LO) accuracy. The predicted results show that the NLO EW effects have larger impact in the forward eta l region of the A(eta l) contrary to the central eta l region, and is sizable in some of the y(W) ranges of the A(yw). The paper suggests inclusion of the presented EW corrections at NLO to have explicit accounting for the EW effects for the A(eta l) (A(yw)) in phenomenological studies.
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    Higher-order differential cross section calculation for the associated production of a W boson and jets in the electron decay channel at a center-of-mass energy of 13 TeV in proton-proton collisions
    (Tubitak Scientific & Technological Research Council Turkey, 2019) Ocalan, Kadir
    Higher-order cross sections for the production of a W boson in association with jets in the electron decay channel are presented in this study. Cross sections were calculated in a fully differential way using a computational framework based on proton-proton collisions at a center-of-mass energy of 13 TeV. The differential cross section predictions in the fiducial phase-space were compared at next-to-leading order (NLO) and next-to-NLO (NNLO) in perturbative quantum chromodynamics (pQCD). The differential results are reported for the variables including the jet multiplicity, the invariant mass of the W boson, transverse momentum, the jet rapidity, and the electron pseudorapidity that are sensitive to higher-order corrections in pQCD. The presented differential cross sections were generally improved in precision in the NNLO calculation. The total cross sections at NLO and NNLO are also reported in the fiducial phase-space. More accurate results were obtained in the calculation of the total production rates at NNLO. The results in all the calculations are given in the W+ and the W (-) boson decay channels separately to better assess the impact of the inclusion of higher-order corrections in those processes.
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    Impact of lepton pT threshold on charge asymmetry predictions for inclusive W boson production in pp collisions at 13 TeV
    (Iop Publishing Ltd, 2021) Ocalan, Kadir
    This paper presents the impact of the lepton transverse momentum threshold on the boson charge asymmetry predictions in perturbative QCD for the inclusive production in proton-proton () collisions. The predictions are obtained at various low- thresholds 20, 25, 30, and 40 GeV in a fiducial region encompassing both the central and forward detector acceptances in terms of the lepton pseudorapidity. The predicted distributions for the lepton charge asymmetry, which is defined by (), at the nextto-next-to-leading order (NNLO) accuracy are compared with the CMS and LHCb data at 8 TeV center-of-mass collision energy. The 8 TeV predictions reproduce the data fairly well within the quoted uncertainties. The predictions from the CT14 parton distribution function (PDF) model are in a slightly better agreement with the data over the other PDF sets that are tested. The 13 TeV predictions using various thresholds are reported for and the charge asymmetries that are defined in terms of the differential cross sections in bins of the boson rapidity () and transverse momentum (). The NNLO predictions for the,, and distributions are assessed to be in close correlation with the value. The and distributions are particularly shown to be more correlated at a higher threshold. The distributions are also reported from the merged predictions with improved accuracy by the inclusion of the next-to-next-to-next-to-leading logarithm (N3LL) corrections, i.e., at NNLO+N3LL. The predicted distributions from various thresholds represent a finer probe in terms of the capability to provide more constraints on the ratio of and quark distribution functions in the parton momentum fraction range. Keywords: high energy physics phenomenology, perturbative QCD calculations, W bosons, W boson charge asymmetries, lepton transverse momentum threshold
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    NNLO QCD predictions of electron charge asymmetry for inclusive pp ? W plus X production in forward region at 13 and 14 TeV
    (Iop Publishing Ltd, 2021) Ocalan, Kadir
    This paper presents perturbative QCD predictions of the electron charge asymmetry for inclusive W-+/- + X -> e(+/-)nu + X production in proton-proton (pp) collisions. Perturbative QCD calculations are performed at nextto-next-to-leading order (NNLO) accuracy using different parton distribution function (PDF) models at 8, 13, and 14 TeV center-of-mass energies of CERN LHC pp collisions. NNLO calculations are performed for electrons with transverse momenta above 20 GeV in the forward electron pseudorapidity region 2.0 <= eta(e) <= 4.25. NNLO predictions are first compared at 8 TeV with the measurements of the LHCb experiment at the LHC for the W+/W- cross section ratio and charge asymmetry distributions. The 8 TeV predictions using NNPDF3.1, CT14, and MMHT2014 PDF sets are reported to be in good agreement with the LHCb data for the entire eta(e) region, justifying the extension of the calculations to 13 and 14 TeV energies. The charge asymmetry predictions at NNLO accuracy are reported in the forward eta(e) bins at 13 and 14 TeV and compared among NNPDF3.1, CT14, and MMHT2014 PDF sets. Overall, the predicted W-+/- differential cross-section and charge asymmetry distributions based on different PDF sets are found to be consistent with each other for the entire eta(e) region. The charge asymmetry distributions are shown to be more sensitive to discriminate among different PDF models in terms of the 14 TeV predictions.
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    Precise calculation of differential cross sections for the Z boson plus jets production in proton-proton collisions at a center-of-mass energy of 13 TeV
    (Tubitak Scientific & Technological Research Council Turkey, 2019) Ocalan, Kadir
    The differential cross section predictions for the associated production of a Z boson and jets are presented in proton-proton collisions at a center-of-mass energy of 13 TeV. The differential cross sections are calculated by using a computational framework for the dielectron decay mode of the Z boson. Higher-order differential cross section predictions are obtained in the fiducial phase space and are compared at next-to-leading order (NLO) and next-to-NLO (NNLO) in perturbative quantum chromodynamics (pQCD). The predicted results are reported as functions of the variables including the jet multiplicity, the invariant mass of the Z boson, and transverse momenta of the Z boson and of the decay products. The predicted results are also reported for the angular correlation variables for the final state decay products. The differential results are generally improved in precision upon inclusion of the NNLO corrections. The total cross sections are calculated in the fiducial phase space at different orders in pQCD up to NNLO. The total production rates are predicted more accurately by the NNLO calculation.
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    Vector boson production in association with jets at CMS
    (Elsevier Science Bv, 2018) Yalvac, Metin; Ocalan, Kadir
    The production cross section of highly boosted vector bosons (V = W, Z or gamma) recoiling against jets is studied, with CMS data, differentially as function of the transverse momentum and angular correlations of the final state particles. The measurements are confronted with different state-of-the-art theory predictions that include next-to-leading order calculations and matrix-element plus parton shower event simulations.
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    Z/W plus jets production at 8/13 TeV in CMS
    (E D P Sciences, 2016) Ocalan, Kadir
    The production of vector bosons (Z and W) in association with jets provides a stringent test of perturbative QCD and is a background process in searches for new physics. Differential cross section measurements of vector bosons produced in association with jets and heavy flavour quarks in proton-proton collisions at center of mass energies of 8 TeV and 13 TeV in the CMS experiment at the LHC are presented. The measurements are compared to next-to-leading order calculations and event simulations that devise matrix element calculations interfaced with parton showers.