Speaker
Description
Heavy quarks (charm and beauty) are produced at the initial stages of the relativistic hadronic collisions in hard scattering processes. The study of heavy-flavor production provides a stringent test to perturbative Quantum Chromo-Dynamics (pQCD) calculations in proton-proton (pp) collisions and can help in disentangling cold nuclear matter (CNM) effects in proton-lead (p--Pb) collisions. Analysis of charm production as a function of charged-particle multiplicity lets us investigate the role of multi-parton interactions (MPI) in particle production, color-reconnection (CR) mechanisms in hadronization, and the interplay between the hard and soft particle production in pp and p--Pb collisions. Heavy-flavor production measurements in high multiplicity pp and p--Pb collisions indicate possible modification of the particle spectra compared to minimum bias measurements. These results raise questions about the collective nature of the QCD matter produced in small systems, which are typically observed in Pb--Pb collisions.
In this contribution, measurements of open heavy-flavor production as a function of multiplicity, via the study of the $\mathrm{D}$-meson and heavy-flavor decay leptons using self-normalized yields in pp collisions at the center-of-mass energy of $\sqrt{s} = 13$ TeV are discussed. The self normalised yields increase stronger than linearly with increasing charged-particle multiplicity and tend to have a steeper trend with increasing $p_{\rm{T}}$. Comparisons are made with similar measurements of J$/\psi$ at $\sqrt{s} = 13$ TeV and D-mesons at $\sqrt{s} = 7$ TeV and various model predictions. The $\Lambda_{\rm{c}}^{+}/\rm{D}^{0}$ and $\rm{D^{+}_{s}/D^0}$ ratio measurements in different multiplicity intervals in pp collisions at $\sqrt{s} = 13$ TeV are also shown. Enhancement of $\Lambda_{\rm{c}}^{+}/\rm{D}^{0}$ is observed when compared to $\rm{e^+e^-}$ collisions and with increasing multiplicity, whereas no such behaviour is seen for $\rm{D^{+}_{s}/D^0}$. Finally, the nuclear modification factor calculations are shown for open charm hadrons at $\sqrt{s} = 5.02$ TeV in p--Pb collisions. Measurement of D-meson $Q_{\rm{cp}}$ and elliptic flow of heavy-flavor decay leptons in similar systems are presented. Both these measurements hint towards a possible collective behaviour of the QCD matter forming in high multiplicity p--Pb collisions.
| Preferred track | Hadronic Issues in Heavy-Flavour Physics |
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