We study the inclusive hadroproduction of D0, D+, D*+, and D(s)+ mesons at next-to-leading order in the parton model of quantum chromodynamics endowed with universal nonperturbative fragmentation ...functions fitted to e+e- annihilation data from CERN LEP1. Working in the general-mass variable-flavor-number scheme, we resum the large logarithms through the evolution of the fragmentation functions and, at the same time, retain the full dependence on the charm-quark mass without additional theoretical assumptions. In this way, the cross section distributions in transverse momentum recently measured by the CDF Collaboration in run II at the Fermilab Tevatron are described within errors.
We present new sets of next-to-leading order fragmentation functions describing the production of charged pions, kaons and protons from the gluon and from each of the quarks, obtained by fitting to ...all relevant data sets from
e
+
e
−
annihilation. The individual light quark flavour fragmentation functions are obtained phenomenologically for the first time by including in the data the light quark tagging probabilities obtained by the OPAL Collaboration.
We present new sets of fragmentation functions for charged pions, charged kaons, and protons, both at the leading and next-to-leading orders. They are fitted to the scaled-momentum distributions of ...these hadrons measured in
e
+
e
− annihilation on the
Z-boson resonance at CERN LEP1 and SLAC SLC. These data partly come as light-, charm-, bottom-quark-enriched and gluon-jet samples, which allows us to treat all partons independently, after imposing the SU(2) flavour symmetry relations. In order to gain sensitivity to the scaling violation in fragmentation, we also include data from SLAC PEP, with center-of-mass energy
s
=29
GeV, in our fits. This allows us to also determine the strong-coupling constant, with a competitive error. LEP1 data on the longitudinal cross section as well as DESY DORIS and PETRA data at lower energies nicely agree with theoretical predictions based on our fragmentation functions.
The hadroproduction of the radially excited heavy-quarkonium states ψ(2S) and ϒ(3S) at high energies is studied in the parton Reggeization approach and the factorization formalism of nonrelativistic ...QCD at lowest order in the strong-coupling constant αs and the relative heavy-quark velocity v. A satisfactory description of the ψ(2S) transverse-momentum (pT) distributions measured by ATLAS, CMS, and LHCb at center-of-mass energy S=7 TeV is obtained using the color-octet long-distance matrix elements (LDMEs) extracted from CDF data at S=1.96 TeV. The importance of the fragmentation mechanism and the scale evolution of the fragmentation functions in the upper pT range, beyond 30 GeV, is demonstrated. The ϒ(3S) pT distributions measured by CDF at S=1.8 TeV and by LHCb at S=7 TeV and forward rapidities are well described using LDMEs fitted to ATLAS data at S=7 TeV. Comparisons of polarization measurements by CDF and CMS at large pT values with our predictions consolidate the familiar problem in the ψ(2S) case, but yield reasonable agreement in the ϒ(3S) case.
We present a detailed discussion of the collinear subtraction terms needed to establish a massive variable-flavor-number scheme for the one-particle inclusive production of heavy quarks in hadronic ...collisions. The subtraction terms are computed by convoluting appropriate partonic cross sections with perturbative parton distribution and fragmentation functions relying on the method of mass factorization. We find (with one minor exception) complete agreement with the subtraction terms obtained in a previous publication by comparing the zero-mass limit of a fixed-order calculation with the genuine massless results in the \({\overline{\mathrm{MS}}}\) scheme. This presentation will be useful for extending the massive variable-flavor-number scheme to other processes.
We study the cross sections for the inclusive production of ψ(2S) and X(3872) hadrons in p p collisions at the LHC at two different center-of-mass energies and compare them with experimental data ...obtained by the ATLAS, CMS, and LHCb Collaborations.
We consider two-loop two-, three-, and four-point diagrams with elliptic subgraphs involving two different masses, m and M. Such diagrams generally arise in matching procedures within nonrelativistic ...QCD and QED and are relevant, e.g., for top-quark pair production at threshold and parapositronium decay. We present the obtained results in several different representations: series solution with binomial coefficients, integral representation, and representation in terms of generalized hypergeometric functions. The results are valid up to terms of O(ε) in d=4−2ε space-time dimensions. In the limit of equal masses, m=M, the obtained results are written in terms of elliptic constants with explicit series representations.
The Spin Physics Detector (SPD) is a future multipurpose experiment foreseen to run at the NICA collider, which is currently under construction at the Joint Institute for Nuclear Research (JINR, ...Dubna, Russia). The physics program of the experiment is based on collisions of longitudinally and transversely polarized protons and deuterons at s up to 27 GeV and luminosity up to 1032 cm−2 s−1. SPD will operate as a universal facility for the comprehensive study of the unpolarized and polarized gluon content of the nucleon, using complementary probes such as: charmonia, open-charm, and prompt-photon production processes.
The aim of this work is to provide a thorough review of the physics objectives that can potentially be addressed at SPD, underlining related theoretical aspects and discussing relevant experimental results when available. Among different pertinent phenomena particular attention is drawn to the study of the gluon helicity, gluon Sivers and Boer-Mulders functions in the nucleon, as well as the gluon transversity distribution in the deuteron, via the measurement of single and double spin asymmetries.
On the b-quark running mass in QCD and the SM Bednyakov, A.V.; Kniehl, B.A.; Pikelner, A.F. ...
Nuclear physics. B,
March 2017, 2017-03-00, 2017-03-01, Letnik:
916, Številka:
C
Journal Article
Recenzirano
Odprti dostop
We consider electroweak corrections to the relation between the running MS‾ mass mb of the b quark in the five-flavor QCD×QED effective theory and its counterpart in the Standard Model (SM). As a ...bridge between the two parameters, we use the pole mass Mb of the b quark, which can be calculated in both models. The running mass is not a fundamental parameter of the SM Lagrangian, but the product of the running Yukawa coupling yb and the Higgs vacuum expectation value. Since there exist different prescriptions to define the latter, the relations considered in the paper involve a certain amount of freedom. All the definitions can be related to each other in perturbation theory. Nevertheless, we argue in favour of a certain gauge-independent prescription and provide a relation which can be directly used to deduce the value of the Yukawa coupling of the b quark at the electroweak scale from its effective QCD running mass. This approach allows one to resum large logarithms ln(mb/Mt) systematically. Numerical analysis shows that, indeed, the corrections to the proposed relation are much smaller than those between yb and Mb.
We study inclusive Λc±-baryon production in p p collisions in the general-mass variable-flavor-number scheme and compare with data from the LHCb, ALICE, and CMS collaborations. We perform a new fit ...of the c → Λc+ fragmentation function combining e+ e− data from OPAL and Belle. The agreement with LHC data is slightly worse compared with a calculation using an older fragmentation function, and the tension between different determinations of Λc± production cross sections from the LHC experimental collaborations is not resolved. The ratio of data for Λc+-baryon and D0-meson production seems to violate the universality of c-quark to c-hadron fragmentation.
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