11th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions

Heavy quarks are produced in the early stage of heavy ion collisions due to their large mass, and experience the entire evolution of the QCD medium. The baryon-to-meson ratio, in particular, the $\Lambda_c^+$/$D^0$ ratio, provides valuable information on charm hadronization mechanisms, testing the role of coalescence in the Quark-Gluon Plasma created in PbPb collisions. In $p$Pb collisions,...

We consider the problem of including a finite number of scattering centers in dynamical energy loss and classical DGLV formalism. Previously, either one or an infinite number of scattering centers were considered in energy loss calculations, while attempts to relax such approximations were largely inconclusive or incomplete. In reality, however, the number of scattering centers is 4-5 at RHIC...

A nonperturbative charm production contribution, known as intrinsic charm, has long been speculated. While it has yet to be satisfactorily proven, there have been recent tantalizing hints. Several experiments, either taking data or
planned, could proivde definitive evidence in the next few years. Experiments that have taken $J/\psi$ and $D$ meson data include SeaQuest at Fermilab and SMOG...

The Low's theorem is applied to the soft gluon emission from heavy quark scattering in quark-gluon plasma (QGP). The QGP is described by the DQPM (Dynamical QuasiParticle Model) which reproduces the EoS from lQCD at finite temperature and chemical potential. We show that if the emitted gluon is soft and of long wavelength, the scattering amplitude can be factorized into the scattering part and...

Charmonia production in RHIC is one of the best probes of the QGP state of matter which is created in those collisions. However, the genuine origin of such charmonia is under debate: statistical hadronisation (SH) model considers them as formed at the freeze out while transport models contain 2 components : the primordial charmonia, produced early and subject to decay rate as well as the...

Quarkonia are excellent probes of deconfinement in heavy-ion collisions. For J/$\psi$, a bound state of ${c}\bar{c}$ quarks, its production yield is sensitive to color screening and dissociation in the medium. However, at LHC energies, the charmonium regeneration is expected to be significantly larger than at RHIC and SPS energies, since the density of uncorrelated charm-anticharm ($c\bar{c}$)...

The second-order Fourier coefficients ($v_{2}$) of $\Upsilon$(1S) and J/$\psi$ mesons in high-multiplicity pPb collisions is studied using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy 8.16 TeV. The dimuons used to reconstruct the heavy quarkonium states are correlated with charged hadrons using long-range two-particle correlation techniques. The measurement...

The second- and third-order Fourier coefficients of charmonium states are measured in PbPb collisions with CMS. With this new analysis, extending to a higher $p_\mathrm{T}$ region, we investigate further the high-$p_\mathrm{T}$ J/$\psi$ $v_{2}$ in heavy ion collisions. The nonprompt J/$\psi$ $v_{2}$ probes the different behavior of charm and bottom quarks induced by interactions with the QGP...

Suppression of open heavy flavors and quarkonia in heavy-ion collisions is among the most informative probes of the quark-gluon plasma. Interpreting the full wealth of data obtained from the collision events requires a precise understanding of the evolution of heavy quarks and quarkonia as they propagate through the nearly thermal and strongly coupled plasma. Only in the past few years,...

Measurements of bottomonium states in heavy-ion collisions provide a powerful tool to study both initial-state effects on heavy-quark production and final-state interactions between heavy quarks and the quark-gluon plasma (QGP). The ATLAS experiment at LHC has measured the production of bottomonium states $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S), in Pb+Pb and $pp$ collisions at a...

We present the first study of coherent exclusive quarkonium (J/psi, Upsilon) photoproduction in ultraperipheral nucleus-nucleus collisions (UPCs) at the LHC in the framework of collinear factorization and next-to-leading order (NLO) perturbative QCD. We make predictions for the J/psi and Upsilon rapidity distributions for the cases of lead (Pb) and oxygen (O) beams and quantify their...

We extend a previously constructed T-matrix approach for heavy quarks in the quark-gluon plasma (QGP) to include inverse-mass (1/M) corrections, i.e. the spin-orbit, spin-spin and tensor forces, between partons. Based on the vacuum Cornell potential as the interaction kernel for the T-matrix equation, we first confirm that the experimental charmonium and bottomonium spectroscopy in vacuum are...

The LHCb spectrometer has the unique capability to function as a fixed-target experiment by injecting gas into the LHC beampipe while proton or ion beams are circulating. The resulting beam+gas collisions cover an unexplored energy range that is above previous fixed-target experiments, but below the top RHIC energy for AA collisions. Here we present new results on open charm, $J/\psi$, and...

Heavy quarks (i.e. charm and beauty) are powerful tools to characterize the quark-gluon plasma (QGP) produced in heavy-ion collisions. Although they are initially produced out of kinetic equilibrium via hard partonic scattering processes, recent measurements of anisotropic flow of charmed hadrons [1] pose the question regarding the possible thermalization of heavy quarks in the medium. Our...

Bottomonia, the heaviest known mesons, represent major probes of strongly interacting matter properties. In the context of nuclear collisions, the binding energies separating the $\Upsilon$(nS) states (n=1, 2, or 3) offer an experimental handle to characterize the medium formed. In this talk, we study the modification of the production of the three $\Upsilon$ mesons in both pPb and PbPb...

The hadronization process is a well-known non-perturbative process, which is happening in both elementary collisions such as $p+p$, $e^++e^-$ collisions, and also the relativistic heavy ion collisions. Studying the hadronization mechanism is crucial for understanding the QCD in low-energy regions.
In elementary collisions, the hadronization process is usually described by the fragmentation...

In this contribution, we present the new measurements of non-prompt $\mathrm{D}^+$ and $\mathrm{D_s}$ in pp collisions at $\sqrt{s}$ = 13 TeV. Together with the final measurements of non-prompt $\mathrm{D}^0$ and $\Lambda_\mathrm{c}^+$, they are crucial to study the beauty quark hadronisation in proton-proton (pp) collisions and their difference with respect to $\mathrm{e^+e^-}$ collisions. In...

The total rate of heavy quark production can be calculated with perturbative QCD techniques. However, the fraction of heavy quarks that pair with a light quark (forming mesons) versus the fractions combine with two other quarks (baryons) baryons or 3 or more other quarks (exotic states) is sensitive to the nonperturbative hadronization process. LHCb is uniquely well suited to study such...

The surprising collectivity signal emerging in small hadronic systems for light and heavy quarks raises the question whether a quark-gluon plasma is created in those systems too. The conjectured QGP formation could also enhance baryon production because of coalescence processes. Moreover, strangeness enhancement signals have been observed. Recent measurements show charm baryon-to-meson ratios...

In this contribution, new results for beauty measurements with ALICE are presented. The production of beauty hadrons can be accessed with measurements of leptons from beauty- and charm-hadron decays as well as the reconstruction of non-prompt charmed hadrons.
We show the nuclear modification factor of electrons from beauty hadron decays in Pb-Pb collisions at $\sqrt{s_{\rm \scriptscriptstyle...

While perturbative QCD is sufficient for understanding parton energy loss at large transverse momentum ($p_\mathrm{T}$) in heavy-ion collisions, a simultaneous description of the heavy flavor nuclear modification factor ($R_\mathrm{AA}$) and elliptic flow coefficient ($v_2$) at low to intermediate $p_\mathrm{T}$ still remains challenging due to non-perturbative interactions between heavy...

We present a novel approach to nonperturbatively estimate the heavy quark momentum diffusion coefficient, which is a key input for the theoretical description of heavy quarkonium production in heavy ion collisions, and is important for the understanding of the elliptic flow and nuclear suppression factor of heavy flavor hadrons. In the heavy quark limit, this coefficient is encoded in the...

The understanding of the charm-quark hadronisation in high-energy hadronic collisions has recently improved. The production of D mesons relative to each other is compatible with those measured in $\mathrm{e^{+}e^{-}}$ collisions. The charm baryon-to-meson yield ratios show an enhancement from those measured at lepton colliders. This modification depends on the charged-particle multiplicity....

It has been a challenge to understand the experimental data on both the nuclear modification factor and elliptic flow of $D^0$ mesons in $p−Pb$ collisions at LHC energies. In this $\rm{work^{[1]}}$, we study these observables with an improved multi-phase transport model. After including the Cronin effect (or transverse momentum broadening) and independent fragmentation for charm quarks, we...

In recent years, a significant theoretical effort has been made towards a dynamical description of quarkonia inside the Quark-Gluon Plasma (QGP), using the open quantum systems formalism. In this framework, one can get a real-time description of a quantum system (here the quarkonium) in interaction with a thermal bath (the QGP) by integrating out the bath degrees of freedom and studying the...

High-multiplicity measurements in pp and p-Pb collisions have revealed the presence of phenomena typically attributed to the creation of a quark-gluon plasma (QGP). Events with multiple parton-parton interactions (MPIs) have been proposed as one possible explanation of this observation. MPIs play a significant role in describing the soft component of the hadronic interactions, and at LHC...

Quarkonia production in hadronic collisions is an important experimental observable that sheds light on the heavy quark interaction with the nuclear medium. While the bound quarkonium states undergo dissociation and recombination in PbPb collisions, in $p$Pb collisions they can suffer from a combination of initial and final state effects such as shadowing and comover breakup. The exotic...

We show that the same QCD formalism that accounts for the suppression of high-$p_T$ hadron and jet spectra in heavy-ion collisions predicts medium-enhanced production of $c\bar{c}$ pairs in jets. Using the formalism of Baier-Dokshitzer-Mueller-Peigné-Schiff and Zakharov we compute the medium-modifications of the gluon splitting into a quark–anti-quark pair and reveal two phenomena: a...

The interaction of heavy quarks with the quark-gluon plasma (QGP) affects their azimuthal distribution and $p_{\rm{T}}$ spectrum, hence measurement of azimuthal anisotropy coefficients ($v_n$) and nuclear modification factors ($R_{\rm{AA}}$) of heavy flavor hadrons turns out to be an important probe of the QGP. However, simultaneous modeling of $v_n$ and $R_{\rm{AA}}$ is still challenging....

We compute the heavy quark momentum diffusion coefficient using effective kinetic theory for a system going through bottom-up isotropization until approximate hydrodynamization. We find that when matching the nonthermal diffusion coefficient to the thermal one for the same energy density, the observed deviations throughout the whole evolution are withing 30% from the thermal value. When...

One of the most prominent features of the quark gluon plasma is its near-perfect fluid behavior. An important outstanding question is establishing the degree to which heavy flavor particles flow with the bulk system. Measurements of the Fourier coefficient v2 of light and heavy flavor hadrons and quarkonia can provide insight into the properties of the medium. At low transverse momentum (pT)...

We present predictions for the suppression of D and B-mesons at $\sqrt{s}=5.5$ TeV at the LHC in Pb+Pb collisions. We assume that the QGP is strongly coupled, and show the centrality and momentum dependence of the nuclear modification factor at midrapidity. We quantify the systematic theoretical uncertainties associated with the mapping of parameters in $N=4$ SYM theory to QCD, as well as the...

Shower development dynamics for a jet traveling through the quark-gluon plasma (QGP) is a multi-scale process, where the heavy flavor mass is an important scale. During the high virtuality portion of the jet evolution in the QGP, emission of gluons from a heavy flavor is modified owing to heavy quark mass. In-medium stimulated radiation of heavy flavor is sensitive to microscopic processes...

The high-intensity beams provided by the CERN SPS in a wide energy interval offer a unique opportunity to investigate the region of the QCD phase diagram at high baryochemical potential.
The NA60+ experiment, proposed for taking data with heavy-ion collisions at the SPS in the next years, has a strong potential of providing new insights into the QCD phase diagram via measurements of rare...

Polarization measurements represent an important tool for the understanding of particle production mechanisms occurring in proton–proton collisions. When considering heavy-ion collisions, quarkonium polarization could also be used to investigate the characteristics of the hot and dense medium, the quark-gluon plasma (QGP) created at LHC energies. It has been hypothesized that quarkonium states...

We show for the first time that heavy flavor quenching and flow can be utilized to probe the equation of state (EoS) of quark-gluon plasma (QGP) produced in relativistic heavy-ion collisions. Based on our quasi-particle linear Boltzmann transport (QLBT) model that is coupled to a (3+1)-dimensional viscous hydrodynamic simulation of the QGP and a hybrid fragmentation-coalescence approach for...

Charmonium production is a probe sensitive to deconfinement in nucleus-nucleus collisions. The production of J/$\psi$ via regeneration within the QGP or at the phase boundary has been identified as an important ingredient for the description of the observed J/$\psi$ nuclear modification factor at the LHC. The $\psi$(2S) production relative to J/$\psi$ is a possible discriminator between the...

J/$\psi$ is an important probe to study the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. Measurements of J/$\psi$ yield suppression in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV suggest that J/$\psi$ production in heavy-ion collisions is affected by the interplay of several effects, such as dissociation, regeneration in the QGP, and the cold nuclear...

Heavy quarks are one of the most important probes to study the properties of quark-gluon plasma (QGP). We present new results on nuclear modification factors of $\rm{B}_{\rm{s}}^{0}$ and $\rm{B}^{+}$ mesons in pp and PbPb collisions at 5.02 TeV, using data recorded with the CMS detector in 2017 and 2018. The reported B meson nuclear modification factors over an extended transverse momentum...