Charm Quark Research Articles

Heavy-flavor transport and hadronization in a small fireball

We study heavy-flavor hadron production in high-energy pp collisions, assuming the formation of a small, deconfined and expanding fireball where charm quarks can undergo rescattering and hadronization. We adopt the same in-medium hadronization mechanism developed for heavy-ion collisions, which involves Local Color-Neutralization (LCN) through recombination of charm quarks with nearby opposite color charges from the background fireball. Diquark excitations in the hot medium favor the formation of charmed baryons. The recombination process, involving closely aligned partons from the same fluid cell, effectively transfers the collective flow of the system to the final charmed hadrons. This framework can qualitatively reproduce the observed experimental findings in heavy-flavor particle-yield ratios, pT -spectra and ellipticflow coefficients. Our results provide new, complementary support to the idea that the collective phenomena observed in small systems have the same origin as those observed in heavy-ion collisions.

Experimental overview on open-heavy flavours

Heavy flavours, i.e. charm and beauty quarks, are recognised as excellent probes of the colour-deconfined medium created in ultrarelativistic heavy–ion collisions, the quark–gluon plasma (QGP). In this document, the most recent measurements of heavy-flavour hadrons in heavy-ion collisions are summarised. Measurements of nuclear modification factors and angular anisotropies of open charm and beauty hadrons are reported to investigate the properties of the heavy-quark interactions in the QGP. A particular focus is given to the measurement of heavy-flavour baryons and hadrons with strangequark content for the study of the hadronisation mechanisms in both heavy–ion and proton–proton collisions. Finally, the polarisation of the charm vector mesons D*+ and J/ψ in heavy–ion collisions is presented.

Recent charmonium measurements in Pb–Pb collisions with ALICE

Charmonia have long been recognized as a valuable probe of the nuclear matter in extreme conditions, the strongly interacting medium created in heavy-ion collisions known as quark-gluon plasma (QGP). At LHC energies, the (re-)generation process due to the abundantly produced charm quarks, was found to considerably affect measured charmonium observables. Comprehensive production measurements of charmonia, including both ground and excited states, are crucial to discriminate among different (re-)generation scenarios assumed in theoretical calculations. In addition, the spin-alignment of charmonia can be affected by the strong magnetic field and the large angular momentum of the medium in non-central heavy-ion collisions. Finally, the non-prompt charmonium, grants a direct insight into the nuclear modification factor of beauty hadrons, which is expected to be sensitive to the energy loss experienced by the ancestor beauty quarks inside the QGP. In this contribution, newly published results of inclusive, prompt and non-prompt J/ψ production, obtained in Pb–Pb collisions at √SNN = 5.02 TeV, are presented. Recently published results of J/ψ polarization with respect to the event plane at forward rapidity in Pb–Pb collisions at √SNN = 5.02 TeV are also discussed. Results are compared to available model calculations.

Fluid dynamics of charm quarks in the quark-gluon plasma

Fluid dynamics of charm quarks in the quark-gluon plasma

Low-energy matrix elements of heavy-quark currents

In QCD at energies well below a heavy-quark threshold, the heavy-quark vector current can be represented via local operators made of the lighter quarks and of the gluon fields. We extract the leading perturbative matching coefficients for the two most important sets of operators from known results. As an application, we analytically determine the O(αs3)mc2/mb2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{O}(\\alpha _s^3)m_c^2/m_b^2$$\\end{document} effect of the bottom quark current on the R(s) ratio below the bottom but above the charm threshold. For the low-energy representation of the charm quark current, the two most important operators are given by the total divergence of dimension-six gluonic operators. We argue that the charm magnetic moment of the nucleon is effectively measuring the forward matrix elements of these gluonic operators and predict the corresponding bottom magnetic moment. Similarly, the contribution of the charm current to R(s≈1GeV2)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R(s\\approx 1\\,\ extrm{GeV}^2)$$\\end{document}, which is associated with quark-disconnected diagrams, is dominantly determined by the decay constants of the ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\omega $$\\end{document} and ϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi $$\\end{document} mesons with respect to the two gluonic operators.

Charm production and fragmentation fractions at midrapidity in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{\ extrm{s}} $$\\end{document} = 13 TeV

Measurements of the production cross sections of prompt D0, D+, D*+, Ds+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\ extrm{D}}_{\ extrm{s}}^{+} $$\\end{document}, Λc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Lambda}_{\ extrm{c}}^{+} $$\\end{document}, and Ξc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Xi}_{\ extrm{c}}^{+} $$\\end{document} charm hadrons at midrapidity in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV with the ALICE detector are presented. The D-meson cross sections as a function of transverse momentum (pT) are provided with improved precision and granularity. The ratios of pT-differential meson production cross sections based on this publication and on measurements at different rapidity and collision energy provide a constraint on gluon parton distribution functions at low values of Bjorken-x (10−5–10−4). The measurements of Λc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Lambda}_{\ extrm{c}}^{+} $$\\end{document} (Ξc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Xi}_{\ extrm{c}}^{+} $$\\end{document}) baryon production extend the measured pT intervals down to pT = 0(3) GeV/c. These measurements are used to determine the charm-quark fragmentation fractions and the cc¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ extrm{c}\\overline{\ extrm{c}} $$\\end{document} production cross section at midrapidity (|y| < 0.5) based on the sum of the cross sections of the weakly-decaying ground-state charm hadrons D0, D+, Ds+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\ extrm{D}}_{\ extrm{s}}^{+} $$\\end{document}, Λc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Lambda}_{\ extrm{c}}^{+} $$\\end{document}, Ξc0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Xi}_{\ extrm{c}}^0 $$\\end{document} and, for the first time, Ξc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Xi}_{\ extrm{c}}^{+} $$\\end{document}, and of the strongly-decaying J/ψ mesons. The first measurements of Ξc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Xi}_{\ extrm{c}}^{+} $$\\end{document} and Σc0,++\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\Sigma}_{\ extrm{c}}^{0,++} $$\\end{document} fragmentation fractions at midrapidity are also reported. A significantly larger fraction of charm quarks hadronising to baryons is found compared to e+e− and ep collisions. The cc¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ extrm{c}\\overline{\ extrm{c}} $$\\end{document} production cross section at midrapidity is found to be at the upper bound of state-of-the-art perturbative QCD calculations.

A review on anisotropic flow in heavy-ion collisions

We present a review of published experimental measurements on anisotropic flow in heavy-ion collisions. Flow coefficients [Formula: see text] are presented for charged and identified hadrons at various beam energies ranging from [Formula: see text][Formula: see text]GeV to 200[Formula: see text]GeV at the Relativistic Heavy Ion Collider (RHIC) and [Formula: see text][Formula: see text]GeV at the Large Hadron Collider (LHC). We present [Formula: see text] and its slope [Formula: see text] and discuss possible first-order Quantum chromodynamics (QCD) phase transition. [Formula: see text] of particles containing heavy quarks (Charm quarks) is also discussed to illustrate the effect of the magnetic field produced in relativistic heavy-ion collisions. We also present flow harmonics ([Formula: see text], [Formula: see text] and [Formula: see text]) for inclusive charged and identified hadrons. We compare the charged particle [Formula: see text] coefficients with hydrodynamics to study and constrain initial conditions in the transport models. The results of identified particle [Formula: see text] from ideal and viscous hydrodynamics are discussed to understand the dynamics and mechanism of particle production in high-energy nuclear collisions.

Viscous QCD medium effects on the bottom quark transport coefficients

The bottom quark transport coefficients, i.e., drag and diffusion coefficients, have been studied for the collisional and soft gluon radiative processes within the viscous QCD medium. The thermal medium effects are incorporated using the effective fugacity quasiparticle model (EQPM). Both the shear and bulk viscous effects at leading order are embedded through the near-equilibrium distribution functions of the quark–gluon plasma (QGP) constituent quasiparticles. The transport coefficients’ dependence on the bottom quark’s initial momentum and QGP temperature have been investigated. The relative dominance of the radiative over the collisional process for the bottom quark seems to occur at a higher initial momentum compared to that of the charm quark. In contrast, the effect of the viscous corrections seems to be more for the charm quark. Furthermore, we also investigate the validity of the Einstein fluctuation–dissipation theorem for our analysis.

Review of Flavor Anomalies

Lepton flavor universality exists in the Standard Model, and hence any observation of the violation of this universality will be a hint for new physics. Recent experimental searches for processes violating this symmetry have attracted much attention among theorists and experimentalists alike. In recent years, such hints have been observed in flavor changing neutral current weak processes such as b→sll and charged current weak processes such as b→clν processes by collider experiments like Belle, Belle II, BaBar, LHCb, ATLAS, and CMS collaborations, where b,s,c are the bottom, strange, and charm quarks, respectively, and l,ν stand for lepton and the corresponding lepton neutrino, respectively. This article is a review of some of the interesting anomalies observed in the B-sector and includes decays of Bs mesons.

Complementary constraints on Zbb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ Zb\\overline{b} $$\\end{document} couplings at the LHC

We propose a new strategy to probe the Z boson couplings to bottom and charm quarks at the LHC. In this work we mainly focus on the case of bottom quarks. Here, the Z boson is produced in association with two b-jets and decays to electrons or muons. In this final state, tagging the charge of the b-jets allows us to measure the charge asymmetry and thus to directly probe the Zbb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ Zb\\overline{b} $$\\end{document} couplings. The leptonic final state not only allows us to cleanly reconstruct the Z boson but also to mitigate the otherwise overwhelming backgrounds. Furthermore, while LEP could only scan a limited range of dilepton invariant masses, there is no such limitation at the LHC. Consequently, this allows us to make full use of the interference between the amplitudes mediated by a Z boson and a photon. Using the full high-luminosity LHC dataset of 3 ab−1 and with the current flavor and charge-tagging capabilities would allow us to reject the wrong-sign right-handed coupling solution by 4σ. Further improving the charge-tagging efficiency would disfavor it by 6σ.

Measurement of the non-prompt D-meson fraction as a function of multiplicity in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV

The fractions of non-prompt (i.e. originating from beauty-hadron decays) D0 and D+ mesons with respect to the inclusive yield are measured as a function of the charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV with the ALICE detector at the LHC. The results are reported in intervals of transverse momentum (pT) and integrated in the range 1 < pT< 24 GeV/c. The fraction of non-prompt D0 and D+ mesons is found to increase slightly as a function of pT in all the measured multiplicity intervals, while no significant dependence on the charged-particle multiplicity is observed. In order to investigate the production and hadronisation mechanisms of charm and beauty quarks, the results are compared to PYTHIA 8 as well as EPOS 3 and EPOS 4 Monte Carlo simulations, and to calculations based on the colour glass condensate including three-pomeron fusion.

Resolving the RpA and v2 puzzle of D0 mesons in p−Pb collisions at the LHC

It has been a challenge to understand the experimental data on both the nuclear modification factor and elliptic flow of D0 mesons in p−Pb collisions at LHC energies. In this work, we study these collisions with an improved multi-phase transport model. By including the independent fragmentation and a significant Cronin effect (i.e., transverse momentum broadening) for charm quarks, we provide the first simultaneous description of the D0 meson RpA and v2 data at pT≤8 GeV/c. The model also reasonably describes the D0 meson pT spectra and the low-pT charged hadron spectra, RpA and v2. Our results show that both parton interactions and the Cronin effect are important for the D0 meson RpA, while parton interactions are mostly responsible for the D0 meson v2. It is thus essential to include the Cronin effect for the simultaneous description of the D0 meson RpA and v2. This work implies that the Cronin effect could also be important for heavy hadrons in large systems.

Kaon theory: 50 years later

Abstract We summarize the status of the kaon theory 50 years after the seminal paper of Kobayashi and Maskawa [Prog. Theor. Phys. 49, 652 (1973)], who pointed out that six quarks are necessary to have CP violation in the Standard Model (SM) and presented a parametrization of a 3 × 3 unitary matrix that, after the discovery of the charm quark in 1974 and the b quark in 1977, dominated the field of flavor-changing processes. One of the main goals of flavor physics since then has been the determination of the four parameters of this matrix, which we will choose here to be |Vus|, |Vcb|, and the two angles of the unitarity triangle, β and γ, with |Vus| introduced by Cabibbo in 1963. I will summarize the recent strategy for determination of these parameters without new physics (NP) infection. It is based on the conjecture of the absence of relevant NP contributions to ΔF = 2 processes that indeed can be demonstrated by a negative rapid test: the |Vcb|–γ plot. This in turn allows one to obtain SM predictions for rare K and B decays that are the most precise to date. We present strategies for the explanation of the anticipated anomaly in the ratio ε′/ε and the observed anomalies in b → sμ+μ− transitions that are consistent with our ΔF = 2 conjecture. In particular, the absence of NP in the parameter εK still allows for significant NP effects in ε′/ε and in rare kaon decays, moreover, in a correlated manner. Similarly, the absence of NP in ΔMs combined with anomalies in b → sμ+μ− transitions hints at the presence of right-handed quark currents. We also discuss how the nature of neutrinos, Dirac vs. Majorana ones, can be probed in $K\rightarrow \pi \nu \bar{\nu }$ and $B\rightarrow K(K^{*})\nu \bar{\nu }$ decays. The present status of the ΔI = 1/2 rule and ε′/ε is summarized.

Transverse momentum and multiplicity dependence of varLambda _{c}^{+}/D^{0} ratio in pp collisions at sqrt{s}=13 TeV

We apply an equal-velocity quark combination model to study the varLambda _{c}^{+}/D^{0} ratio in the range p_{T}lesssim 10 GeV/c in pp collisions at sqrt{s}=13 TeV. We decompose the ratio into four parts which are related to quark numbers, light-flavor quark p_{T} spectrum, charm quark p_{T} spectrum, momentum correlation between light and charm quarks, respectively. Their influence on varLambda _{c}^{+}/D^{0} ratio is individually studied. The curvature property of light-flavor quark p_{T} spectrum is the main reason of the non-monotonic p_{T} dependence of varLambda _{c}^{+}/D^{0} ratio exhibited in high multiplicity events. Moreover, the multiplicity dependence of varLambda _{c}^{+}/D^{0} ratio as the function of p_{T} is mainly because of the multiplicity dependence of light-flavor quark p_{T} spectrum. Using the light-flavor quark p_{T} spectrum obtained from experimental data of light-flavor hadrons and charm quark p_{T} spectrum obtained from FONLL and/or PYTHIA calculations, the p_{T} dependence of experimental data of varLambda _{c}^{+}/D^{0} ratio in high multiplicity events and that in low multiplicity events in pp collisions at sqrt{s}=13 TeV are reasonably understood.

Heavy flavor production in p–p collisions as a function of multiplicity using different modes of Pythia 8

The production of mesons containing charm quarks in p–p collisions at TeV has been explored as a function of multiplicity using Pythia 8 event generator. The effects of various processes at the partonic level such as different modes of color reconnection and rope hadronization have been studied. The comparison of relative yields (Yield/⟨Yield⟩) of D-mesons and J/ψ as a function of charged-particle multiplicity for various transverse momentum (p T) ranges, measured by the ALICE experiment with the estimations of the Pythia 8 model is performed. The results are in reasonable agreement within the framework of microscopic processes. The relative yields of B-mesons have also been predicted for various pT intervals (1 <pT< 20 GeV/c) with Pythia 8 in p–p collisions at TeV.

Search for a light charged Higgs boson in t → H±b decays, with H± → cb, in the lepton+jets final state in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV with the ATLAS detector

A search for a charged Higgs boson, H±, produced in top-quark decays, t → H±b, is presented. The search targets H± decays into a bottom and a charm quark, H± → cb. The analysis focuses on a selection enriched in top-quark pair production, where one top quark decays into a leptonically decaying W boson and a bottom quark, and the other top quark decays into a charged Higgs boson and a bottom quark. This topology leads to a lepton-plus-jets final state, characterised by an isolated electron or muon and at least four jets. The search exploits the high multiplicity of jets containing b-hadrons, and deploys a neural network classifier that uses the kinematic differences between the signal and the background. The search uses a dataset of proton-proton collisions collected at a centre-of-mass energy s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV between 2015 and 2018 with the ATLAS detector at CERN’s Large Hadron Collider, amounting to an integrated luminosity of 139 fb−1. Observed (expected) 95% confidence-level upper limits between 0.15% (0.09%) and 0.42% (0.25%) are derived for the product of branching fractions B\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{B} $$\\end{document}(t → H±b) × B(H± → cb) for charged Higgs boson masses between 60 and 160 GeV, assuming the SM production of the top-quark pairs.

Selected lattice QCD results on hadron structure

We present recent results on hadron structure using lattice QCD simulations with physical values of the light, strange and charm quark masses. We overview progress on quantities that probe the three-dimensional structure of the nucleon focusing on recent results on Mellin moments and the direct computation of the x-dependence of parton distribution functions employing mainly the quasi-parton distribution approach within the large momentum effective theory.

Production cross section of heavy quarks in e−p interaction at the NLO approximation

We present the production cross section of heavy quarks σcc¯, σbb¯ and σtt¯ at the next-to-leading order in the electron-proton interaction by using the quarks and gluon distribution functions at the initial scale Q02. To do this, we use a fitted form of the heavy quark coefficient functions for deep-inelastic lepton-hadron scattering to obtain the structure functions of heavy quarks. Then, we calculate the reduced cross section of heavy quarks by using the structure functions and subsequently present the single differential and the integrated cross section of heavy quarks at the center-of-mass energies of s=319GeV, 1.3TeV and 3.5TeV in the electron-proton collision. The obtained numerical results of the cross section of the charm and beauty quarks are compared with the HERA data, which is a combination from the results of the H1 and ZEUS detectors. Furthermore, we present the production cross section of top quark as a direct prediction from our calculations.

First-principle calculation of the [formula omitted] decay width from lattice QCD

We perform a lattice QCD calculation of the ηc→2γ decay width using a model-independent method that requires no momentum extrapolation of the off-shell form factors. This method also provides a straightforward and simple way to examine the finite-volume effects. The calculation is accomplished using Nf=2 twisted mass fermion ensembles. The statistically significant excited-state effects are observed and eliminated using a multi-state fit. The impact of fine-tuning the charm quark mass is also examined and confirmed to be well-controlled. Finally, using three lattice spacings for the continuum extrapolation, we obtain the decay width Γηcγγ=6.67(16)stat(6)syst keV, which differs significantly from the Particle Data Group’s reported value of Γηcγγ=5.4(4) keV (2.9σ tension). We provide insight into the comparison between our findings, previous theoretical predictions, and experimental measurements.

NLO + parton-shower generator for varvec{Wc} production in the POWHEG BOX RES

We present the implementation of a next-to-leading-order plus parton-shower event generator for the hadronic production of a heavy charm quark accompanied by a leptonically-decaying W boson in the POWHEG BOX RES framework. We consider both signatures, i.e. pprightarrow c, ell ^- {bar{nu }}_{ell } and pprightarrow {bar{c}} ,ell ^+ {nu }_{ell }, and we include exactly off-shell and spin-correlation effects, as well as off-diagonal Cabibbo–Kobayashi–Maskawa contributions. We present particle-level results, obtained interfacing our code with the Herwig7.2 and Pythia8.3 shower Monte Carlo event generators, including hadronization and underlying-event effects, and compare them against the data collected by the CMS Collaboration at sqrt{s}=13 TeV.