Beauty Cross Sections Research Articles

Phenomenological investigation of the beauty content of a proton in the framework of kt -factorization using Kimber-Martin-Ryskin and Martin-Ryskin-Watt unintegrated parton distributions

In this paper, we address the reduced beauty cross section [σredbb¯(x,Q2)] and the beauty structure function [F2bb¯(x,Q2)], to study the beauty content of a proton. We calculate σredbb¯ and F2bb¯ in the kt-factorization formalism by using the integral form of the Kimber-Martin-Ryskin and Martin-Ryskin-Watt unintegrated parton distribution function (KMR and MRW-UPDF) with the angular ordering constraint (AOC) and the MMHT2014 PDF set as the input. Recently Guiot and van Hameren demonstrated that the upper limit, kmax, of the transverse-momentum integration performed in the kt-factorization formalism should be almost equal to Q, where Q is the hard scale, otherwise it leads to an overestimation of the proton structure function [F2(x,Q2)]. In the present work, we show that kmax cannot be equal to Q at low and moderate energy region, and also by considering the gluon and quark contributions to the same perturbative order and a physical gauge for the gluon, i.e., Aμqμ′=0 in the calculation of F2bb¯ in the kt-factorization formalism, we do not encounter any overestimation of the theoretical predictions due to different choices of kmax>Q. Finally, the resulted σredbb¯ and F2bb¯ are compared to the experimental data and the theoretical predictions. In general, the extracted σredbb¯ and F2bb¯ based on the KMR and MRW approaches are in perfect agreement with the experimental data and theoretical predictions at high energies, but at low and moderate energies, the one developed from the KMR approach has better consistency than that of the MRW approach. Published by the American Physical Society 2024

Recent heavy-flavour measurements with ALICE

In this contribution, an overview on the latest results of the ALICE Collaboration on the production of heavy-flavour hadrons in pp and Pb–Pb collision systems will be presented. Due to their large masses, heavy quarks are produced on shorter time scales than the typical QGP formation time, thus they participate to the system evolution and interact with the medium constituents making the heavy-flavour quarks a perfect probe to investigate the QGP properties. Heavy-flavour production measurements in pp collisions are a needed reference for Pb–Pb studies, to study the hadronization mechanisms in small colliding systems and to test perturbative QCD calculations at the LHC energies. The results presented report charm and beauty cross section measurements with an unprecedented precision down to very low momentum. In addition, results on heavy-flavour production highlight the non-universality of heavy-quark fragmentation fractions among different collision systems and energy scales.

Dielectron production in proton-proton and proton-lead collisions at sNN=5.02TeV

The first measurements of dielectron production at midrapidity ($|\eta_{c}|<0.8$) in proton-proton and proton-lead collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV at the LHC are presented. The dielectron cross section is measured with the ALICE detector as a function of the invariant mass $m_{\rm{ee}}$ and the pair transverse momentum $p_{\rm{T,ee}}$ in the ranges $m_{\rm{ee}}$ < 3.5 GeV/$c^{2}$ and $p_{\rm{T,ee}}$ < 8.0 GeV/$c^{2}$, in both collision systems. In proton-proton collisions, the charm and beauty cross sections are determined at midrapidity from a fit to the data with two different event generators. This complements the existing dielectron measurements performed at $\sqrt{s}$ = 7 and 13 TeV. The slope of the $\sqrt{s}$ dependence of the three measurements is described by FONLL calculations. The dielectron cross section measured in proton-lead collisions is in agreement, within the current precision, with the expected dielectron production without any nuclear matter effects for $\rm{e}^{+}\rm{e}^{-}$ pairs from open heavy-flavor hadron decays. For the first time at LHC energies, the dielectron production in proton-lead and proton-proton collisions are directly compared at the same $\sqrt{s_{\rm{NN}}}$ via the dielectron nuclear modification factor $R_{\rm{pPb}}$. The measurements are compared to model calculations including cold nuclear matter effects, or additional sources of dielectrons from thermal radiation.

Dielectron and heavy-quark production in inelastic and high-multiplicity proton–proton collisions at [formula omitted

The measurement of dielectron production is presented as a function of invariant mass and transverse momentum (pT) at midrapidity (|ye|<0.8) in proton–proton (pp) collisions at a centre-of-mass energy of s=13 TeV. The contributions from light-hadron decays are calculated from their measured cross sections in pp collisions at s=7 TeV or 13 TeV. The remaining continuum stems from correlated semileptonic decays of heavy-flavour hadrons. Fitting the data with templates from two different MC event generators, PYTHIA and POWHEG, the charm and beauty cross sections at midrapidity are extracted for the first time at this collision energy: dσcc¯/dy|y=0=974±138(stat.)±140(syst.)±214(BR)μb and dσbb¯/dy|y=0=79±14(stat.)±11(syst.)±5(BR)μb using PYTHIA simulations and dσcc¯/dy|y=0=1417±184(stat.)±204(syst.)±312(BR)μb and dσbb¯/dy|y=0=48±14(stat.)±7(syst.)±3(BR)μb for POWHEG. These values, whose uncertainties are fully correlated between the two generators, are consistent with extrapolations from lower energies. The different results obtained with POWHEG and PYTHIA imply different kinematic correlations of the heavy-quark pairs in these two generators. Furthermore, comparisons of dielectron spectra in inelastic events and in events collected with a trigger on high charged-particle multiplicities are presented in various pT intervals. The differences are consistent with the already measured scaling of light-hadron and open-charm production at high charged-particle multiplicity as a function of pT. Upper limits for the contribution of virtual direct photons are extracted at 90% confidence level and found to be in agreement with pQCD calculations.

Impact of beauty and charm H1-ZEUS combined measurements on PDFs and determination of the strong coupling

In this QCD analysis, we investigate the impact of recent measurements of heavy-flavor charm and beauty cross sections data sets on the simultaneous determination of Parton Distribution Functions (PDFs) and the strong coupling, $\alpha_s(M^2_Z)$. We perform three different fits based on Variable-Flavour Number Scheme (VFNS) at the Leading Order (LO) and Next-to-Leading Order (NLO) and choose the full HERA run I and II combined data as a new measurement of inclusive Deep Inelastic Scattering (DIS) cross sections for our base data set. We show that including charm and beauty cross sections data reduces the uncertainty of gluon distribution and improves the fit quality up to 4.1\% from leading order to next-to-leading order and up to 1.7\% for only NLO without and with beauty and charm data contributions.

Precision QCD measurements in DIS at HERA

New and recent results on QCD measurements from the H1 and ZEUS experiments at the HERA ep collider are reviewed. The final results on the combined deep-inelastic neutral and charged current cross-sections are presented and their role in the extractions of parton distribution functions (PDFs) is studied. The PDF fits give insight into the compatibility of QCD evolution and heavy flavor schemes with the data as a function of kinematic variables such as the scale Q2. Measurements of jet production cross-sections in ep collisions provide direct proves of QCD and extractions of the strong coupling constants are performed. Charm and beauty cross-section measurements are used for the determination of the heavy quark masses. Their role in PDF fits is investigated. In the regime of diffractive DIS and photoproduction, dijet and prompt photon production cross-sections provide insights into the process of factorization and the nature of the diffractive exchange.

Charm and beauty production in DIS at HERA

Analyses based on the heavy quark data collected by the H1 and ZEUS experiments at the HERA ep collider in the deep inelastic scattering regime are presented. Charm and beauty cross sections are measured and the corresponding heavy quark masses extracted from the data. The running of the charm quark mass can be established using only the HERA data and tested against the predictions of pQCD.

Heavy flavour production at HERA

In this brief review, recent experimental results from the H1 and ZEUS collaborations on heavy flavour production in deep inelastic scattering and photoproduction regimes are summarized. The results cover charm fragmentation fractions, charm and beauty cross sections, F 2 cc and F 2 bb proton structure functions and the running charm- and beauty-quark masses.

Heavy-flavor measurements by the PHENIX experiment at RHIC

In recent years, PHENIX has studied many important observables related to heavy-flavor physics through their leptonic decay measurements including the invariant yield of electrons from nonphotonic sources, and prompt single muons, both of which are dominated by D and B mesons. Charm and beauty cross-sections were measured and compared through single lepton, and lepton–hadron correlations in p + p collisions at GeV. Observables for quarkonia production such as invariant yield and polarization were also measured in p + p collisions. In Au+Au collisions, preliminary results for the RAA for single electrons and a 90% CL upper limit for the suppression of ϒs were produced. And in d+Au collisions, a preliminary RCP study for J/ψ production in different centrality ranges was extracted.

10.1007/s11448-008-1003-y

Inclusive beauty quark production in photon-photon collisions at CERN LEP2 is considered in the framework of the k T -factorization approach. Both direct and resolved photon contributions are taken into account. The unintegrated gluon distributions in a photon are either obtained from the full Catani-Ciafoloni-Fioyani-Marchesini (CCFM) evolution equation or from the Kimber-Martin-Ryskin prescription. The predicted beauty cross section reasonably agrees with recent experimental data taken by the ALEPH collaboration. It is shown that theoretical and experimental studies of the azimuthal correlations in heavy quark production at high energies can serve as a crucial probe of the unintegrated gluon densities.

Measurement of the charm and beauty structure functions using the H1 vertex detector at HERA

Inclusive charm and beauty cross sections are measured in e-p and e+p neutral current collisions at HERA in the kinematic region of photon virtuality 5<Q^2<2000 GeV^2 and Bjorken scaling variable 0.0002<x<0.05. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb^-1. The numbers of charm and beauty events are determined using variables reconstructed by the H1 vertex detector including the impact parameter of tracks to the primary vertex and the position of the secondary vertex. The measurements are combined with previous data and compared to QCD predictions.

Measurement of beauty production from dimuon events at HERA

Beauty production in events containing two muons in the final state has been measured with the ZEUS detector at HERA using an integrated luminosity of 114 pb(-1). A low transverse-momentum threshold for muon identification, in combination with the large rapidity coverage of the ZEUS muon system, gives access to almost the full phase space for beauty production. The total cross section for beauty production in e p collisions at root s = 318 GeV has been measured to be sigma(tot)(ep -> b (b) over barX) = 13.9 +/- 1.5(stat.)(-4.3)(+4.0)(syst.) nb. Differential cross sections and a measurement of b (b) over bar correlations are also obtained, and compared to other beauty cross-section measurements, Monte Carlo models and next-to-leading-order QCD predictions.

Beauty production at HERA using the HI detector

Recent measurements on beauty production at HERA using the HI experiment are presented. The cross section for beauty dijets in photoproduction and the contribution of the inclusive beauty cross section in deep-inelastic scattering (DIS) are shown. The results are based on a method using the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the HI vertex detector. The measurements are compared with the predictions of next-to-leading order (NLO) QCD.

Study of the ALICE performance for the measurement of beauty production

The ALICE experiment is being installed at LHC, where colliding beams with a centre-of-mass energy per nucleon pair of 5.5 TeV in Pb–Pb and 14 TeV in p–p will allow one to test QCD, and in particular to study accurately the characteristics of the quark–gluon plasma. A consequence of the higher energy available with respect to RHIC is the predicted abundant production of heavy quarks (c, b). ALICE will benefit from this to improve our understanding of such collisions thanks to beauty probes. In this paper, we outline the main approaches developed to detect beauty hadrons: several methods are expected to provide complementary measurements of the beauty cross-section up to transverse momenta of about 20 GeV/c.

Beauty production in two-photon interactions at LEP2: k T factorization versus data

Inclusive beauty quark production in photon-photon collisions at CERN LEP2 is considered in the framework of the k T -factorization approach. Both direct and resolved photon contributions are taken into account. The unintegrated gluon distributions in a photon are either obtained from the full Catani-Ciafoloni-Fioyani-Marchesini (CCFM) evolution equation or from the Kimber-Martin-Ryskin prescription. The predicted beauty cross section reasonably agrees with recent experimental data taken by the ALEPH collaboration. It is shown that theoretical and experimental studies of the azimuthal correlations in heavy quark production at high energies can serve as a crucial probe of the unintegrated gluon densities.

Comparison of inclusive charm and beauty cross sections in deep-inelastic scattering at HERA with theoretical predictions

The measurements of inclusive charm and beauty cross sections in deep-inelastic scattering ep collisions at HERA are compared with the predictions of perturbative quantum chromodynamics from the CTEQ and MRST fitting groups, employing a range of theoretical schemes. The differences in the theoretical predictions are discussed and the theoretical uncertainties investigated.

Measurement of $F_2^{c\bar{c}}$ and $F_2^{b\bar{b}}$ at low Q2 and x * using the H1 vertex detector at HERA

Measurements are presented of inclusive charm and beauty cross sections in e^+p collisions at HERA for values of photon virtuality 12 \le Q^2 \le 60 GeV^2 and of the Bjorken scaling variable 0.0002 \le x \le 0.005. The fractions of events containing charm and beauty quarks are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 vertex detector. Values for the structure functions F_2^{c\bar{c}} and F_2^{b\bar{b}} are obtained. This is the first measurement of F_2^{b\bar{b}} in this kinematic range. The results are found to be compatible with the predictions of perturbative quantum chromodynamics and withprevious measurements of F_2^{c\bar{c}}.

Measurement of charm and beauty photoproduction at HERA using [formula omitted] correlations

A measurement of charm and beauty photoproduction at the electron proton collider HERA is presented based on the simultaneous detection of a D*± meson and a muon. The correlation between the D* meson and the muon serves to separate the charm and beauty contributions and the analysis provides comparable sensitivity to both. The total and differential experimental cross sections are compared to LO and NLO QCD calculations. The measured charm cross section is in good agreement with QCD predictions including higher order effects while the beauty cross section is higher.

MSSM Higgs bosons at a future linear collider. Heavy quark production at HERA

We study the potential of the future e + e- linear collider operated at a center-of-mass energy of 500 to 1000 GeV for the measurement of the neutral Higgs boson properties within the framework of the MSSM. The process of associated Higgs boson production with subsequent decays of Higgs bosons into b-quarks is considered. An integrated luminosity of 500 fb -1 is assumed at each energy. The Higgs boson masses and production cross sections are measured by reconstructing the \(\mathrm{b\bar{b}b\bar{b}}\) final state. The precision of these measurements, depending on the Higgs boson masses, is evaluated. Under the assumed experimental conditions, a statistical accuracy ranging from 0.1 to 1.0 GeV is achievable on the Higgs boson mass. The topological cross section \(\mathrm{\sigma(e^ + e^- \rightarrow HA\rightarrow b\bar{b}b\bar{b})}\) can be determined with the relative precision of 1.5-6.6 %. The 5\(\sigma\) discovery limit corresponds to the Higgs mass of around 385 GeV for the degenerate Higgs boson masses in the \(\mathrm{HA\to b\bar{b}b\bar{b}}\) channel at \(\sqrt{s}\) = 800 GeV with integrated luminosity of 500 fb-1. The potential of the Higgs mass determination for the benchmark point SPS 1a for the process \(\mathrm{HA\to b\bar{b}b\bar{b}}\) at \(\sqrt{s}\) = 1 TeV and luminosity 1000 fb-1 is investigated. The possibility of parameter measurements in a CP-violating MSSM scenario is shown. In the second part the inclusive method of charm and beauty cross section measurements in e + p collisions at H1 experiment for values of Q2 > 12 GeV2 is explained. Preliminary plots are shown.

Measurement of $F_2^{c\bar{c}}$ and $F_2^{b\bar{b}}$ at high Q 2 using the H1 vertex detector at HERA

Measurements are presented of inclusive charm and beauty cross sections in e^+p collisions at HERA for values of photon virtuality Q^2 > 150 GeV^2 and of inelasticity 0.1 < y < 0.7. The charm and beauty fractions are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 vertex detector. The data are divided into four regions in Q^2 and Bjorken x, and values for the structure functions F_2^{c\bar{c}} and F_2^{b\bar{b}} are obtained. The results are found to be compatible with the predictions of perturbative quantum chromodynamics.