Hadron Production in Heavy Ion Collisions

Measurements of the nuclear modification factor and elliptic flow of leptons from heavy-flavour hadron decays in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 and 5.02 TeV with ALICE

We present the ALICE results on the nuclear modification factor and elliptic flow of electrons and muons from open heavy-flavour hadron decays at mid-rapidity and forward rapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 and 5.02 TeV for different centrality intervals. The results are compared to model calculations that include interactions of heavy quarks with the medium.

Correlations of Electrons from Heavy Flavor Decay with Hadrons in Au+Au and p+p Collisions

Measurements of electrons from the decay of open-heavy flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled p+p collisions. These measurements indicate that charm and bottom quarks interact with the hot-dense matter produced in heavy-ion collisions much more than expected. Here we extend these studies to two-particle correlations where one particle is an electron from the decay of a heavy-flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide…

Open heavy-flavour production from small to large collision systems with ALICE at the LHC

Heavy quarks are effective probes of the hot and dense nuclear matter, the quark-gluon plasma, produced in ultra-relativistic heavy-ion collisions. Due to the short time scale characterising their production, heavy quarks experience the whole evolution of the system. In particular, measurements of heavy-flavour hadron production in Pb-Pb collisions at LHC energies give insight into the mechanisms of heavy-quark transport in the deconfined matter. In small hadronic systems, pp and p-Pb collisions, heavy-flavour measurements provide the baseline for observations of hot-medium effects in heavy-io…

Azimuthal angular correlations between heavy-flavour decay particles and charged hadrons in pp collisions in ALICE

Heavy quarks produced in pp and heavy ion collisions are studied using heavy-flavour decay electrons and heavy-flavour mesons. Detailed understanding of the production processes and fragmentation of heavy quarks can be obtained by studying the azimuthal angular correlation of heavy-flavour hadrons. The azimuthal angular correlations of heavy-flavour mesons and charged hadrons can be used to disentangle charm and beauty-hadrons in pp collisions. In this contribution the fraction of electrons from beauty-hadron decays in the heavy-flavour decay electron yield is shown as well as the beauty produ…

Measurements of the correlation between electrons from heavy-flavour hadron decays and light hadrons with ALICE at the LHC

In relativistic heavy-ion physics two-particle correlations provide a very useful tool to investigate the Quark-Gluon Plasma (QGP). This observable is sensitive to several of the properties of the QGP such as resonances, interaction of partons with the medium and collective effects (e. g. elliptic flow). In the present work, the correlation function between electrons from heavy-flavour hadron decays and light hadrons was measured in pp and Pb-Pb collisions (central and semi-central). Furthermore, in pp collisions the relative beauty contribution to the total cross section of electrons from hea…

Energy loss, hadronization and hadronic interactions of heavy flavors in relativistic heavy-ion collisions

We construct a theoretical framework to describe the evolution of heavy flavors produced in relativistic heavy-ion collisions. The in-medium energy loss of heavy quarks is described using our modified Langevin equation that incorporates both quasi-elastic scatterings and the medium-induced gluon radiation. The space-time profiles of the fireball is described by a (2+1)-dimensional hydrodynamics simulation. A hybrid model of fragmentation and coalescence is utilized for heavy quark hadronization, after which the produced heavy mesons together with the soft hadrons produced from the bulk QGP are…

Heavy-flavour hadron production

The conventional description of heavy-flavour hadron production in pp collisions is based on a factorisation approach, assuming universal fragmentation functions among collision systems. Recent results on heavy-flavour baryon measurements from the LHC experiments show tensions with model calculations based on this approach and employing fragmentation functions constrained from $\rm e^+e^-$ and $\rm e^-p$ collision experiments. In this contribution, the most recent results from ALICE, ATLAS, CMS and LHCb experiments on the heavy-flavour hadron production in pp collisions at the TeV scale are re…

Measurements of electrons from heavy-flavour hadron decays in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC

Heavy-flavour hadrons, i. e. hadrons carrying charm or beauty quarks, are a well-suited probe to study the Quark-Gluon Plasma (QGP) in relativistic heavy-ion collisions. For this reason, measurements of electrons from heavy-flavour hadron decays have been performed in pp, p-Pb and Pb-Pb collisions at the LHC with the ALICE detector. Results for the nuclear modification factors ($R_{\rm{pA}}$ and $R_{\rm{AA}}$) support a final-state energy loss of heavy quarks in central Pb-Pb collisions and, in semi-central collisions a positive elliptic flow coefficient $v_{2}$ of electrons from heavy-flavour…

Azimuthal angular correlations between heavy-flavour decay electrons and charged hadrons in pp collisions at $\sqrt{s} = 2.76$ TeV in ALICE

In ultra-relativistic heavy-ion collisions heavy quarks (charm and beauty) are produced in hard scattering processes and thus carry relevant information on the properties of the created hot and dense medium. Heavy-flavour hadrons can be measured using electrons from their semileptonic decay channels. The relative contribution of charm and beauty hadrons can be estimated from the study of the near side azimuthal angular correlations between these electrons and charged hadrons. We present the measurement of azimuthal angular correlations between electrons and charged hadrons in pp collisions at …

Heavy Flavor Dynamics in QGP and Hadron Gas

We study heavy flavor evolution in the quark-gluon plasma matter and the subsequent hadron gas created in ultrarelativistic heavy-ion collisions. The motion of heavy quarks inside the QGP is described using our modified Langevin framework that incorporates both collisional and radiative energy loss mechanisms; and the scatterings between heavy mesons and the hadron gas are simulated with the UrQMD model. We find that the hadronic interaction further suppresses the $D$ meson $R_\mathrm{AA}$ at high $p_\mathrm{T}$ and enhances its $v_2$. And our calculations provide good descriptions of experime…

强子化机制（通过重味强子）：实验

Hadronization mechanisms (via heavy-flavour hadrons): Experiment

本文综述了利用不同碰撞系统（e⁺e⁻、pp、pA、AA）中重味强子测量探究强子化机制的最新实验结果，重点展示开放重味测量并与模型预言进行比较。

Angular correlations of heavy-flavour hadron decay electrons and charged particles in pp collisions at $\sqrt{s}$ = 5.02 TeV with ALICE at the LHC

Two-particle azimuthal correlations of electrons from heavy-flavour hadron decays with charged particles can give insight into the properties of heavy-quark production and hadronization into heavy-flavour jets.\\ In this contribution, the ALICE results measured in pp collisions at 5.02 TeV, collected in the LHC Run 2, are presented. The yields of charged particles in the near and away-side correlation peaks and the peak width are compared with PYTHIA calculations.

Probing the incompressibility of dense hadronic matter near QCD phase transition in relativistic heavy-ion collisions

Based on the extended hadronic transport model of relativistic heavy-ion collisions, the incompressibility of dense hadronic matter created in relativistic Au+Au heavy-ion collisions at $\sqrt{s_{NN}} = 3$ GeV is studied. By comparing experimental proton directed flow, productions of strange hadrons $ϕ$, $K^{-}$ as well as their ratio $ϕ/K^{-}$, proton high-order cumulants to the model calculations, a large incompressibility of dense hadronic matter is obtained from nucleon observabels while a rather small incompressibility is needed to fit the data of strange hadrons. This may indicate hadron…

利用重、轻反应系统中粒子发射比探索重离子碰撞中的强子-夸克相变

Exploring hadron-quark phase transition in heavy-ion collisions using particle emission ratios in heavy and light reaction systems

基于AMPT模型研究不同重、轻反应系统中的粒子发射比，发现奇异粒子发射比对强子-夸克相变高度敏感，为重离子碰撞相变探测提供新途径。

Measurement of electrons from heavy-flavour hadron decays in pp and p-Pb collisions with ALICE

ALICE measured electrons from inclusive heavy-flavour hadron decays and beauty-hadron decays at mid-rapidity in pp collisions at \sqrt{s} = 7 TeV and 2.76 TeV and p-Pb collisions at \sqrt{s_{NN}} = 5.02 TeV. For both pp collision energies, p_T-differential electron production cross sections are presented and compared to pQCD predictions. For p-Pb collisions, the p_T-dependent nuclear modification factor of electrons from inclusive heavy-flavour hadron decays is presented.

Multiplicity dependence of heavy-flavour correlations with charged particle and collective effects in p--Pb collisions at $\sqrt{s_\mathrm{NN}}$= 5.02 TeV with ALICE at LHC

Azimuthal correlation studies of heavy-flavour particles with charged particles in p--Pb collisions can give an insight into the cold nuclear matter effects \cite{Andronic:2015wma} on heavy-quark production and hadronization into heavy-flavour jets. Multiplicity-dependent measurements of angular correlations of heavy-flavour particles with charged hadrons allow us to investigate the collective behavior of the system and the initial state effects on heavy flavour hadron production. In addition, they can reveal possible modifications of the heavy-quark fragmentation and hadronization at differen…

Studying Exotic Hadrons in Heavy Ion Collisions

We investigate the possibilities of using measurements in present and future experiments on heavy ion collisions to answer some longstanding problems in hadronic physics, namely identifying hadronic molecular states and exotic hadrons with multiquark components. The yields of a selected set of exotic hadron candidates in relativistic heavy ion collisions are discussed in the coalescence model in comparison with the statistical model. We find that the yield of a hadron is typically an order of magnitude smaller when it is a compact multiquark state, compared to that of an excited hadronic state…

Particle Production in s_NN = 2.76 TeV Heavy Ion Collisions

We obtain within the statistical hadronization model the hadron yields $dh/dy$ in heavy ion reactions at $\sqrt{s_{NN}} = 2.76$ TeV. We discuss the dependence both on hadronization temperature $T$, and on critical hadronization pressure $P$. We consider observables distinguishing the hadronization models and conditions.

Influence of hadronic bound states above $T_c$ on heavy-quark observables in Pb+Pb collisions at at the CERN Large Hadron Collider

We investigate how the possible existence of hadronic bound states above the deconfinement transition temperature $T_c$ affects heavy-quark observables like the nuclear modification factor, the elliptic flow and azimuthal correlations. Lattice QCD calculations suggest that above $T_c$ the effective degrees of freedom might not be exclusively partonic but that a certain fraction of hadronic degrees of freedom might already form at higher temperatures. This is an interesting questions by itself but also has a strong influence on other probes of the strongly interacting matter produced in ultrare…

Production of multi-charmed hadrons by recombination in heavy ion collisions

We study the production of multi-charmed hadrons by recombination in heavy ion collisions by focusing on the production of $Ξ_{cc}$, $Ξ_{cc}^*$, $Ω_{scc}$, $Ω_{scc}^*$, $Ω_{ccc}$ baryons and X(3872) mesons. Starting from the estimation of yields for those hadrons at chemical freeze-out in both the statistical and coalescence model, we evaluate their transverse momentum distributions at mid-rapidity in the coalescence model. We show that yields of multi-charmed hadrons in heavy ion collisions at RHIC and LHC are large enough, and thereby not only multi-charmed hadrons observed so far, e.g., the…

Event engineering studies for heavy flavor production and hadronization in high multiplicity hadron-hadron and hadron-nucleus collisions

Heavy flavor measurements in high multiplicity proton-proton and proton-nucleus collisions at collider energies enable unique insights into their production and hadronization mechanism because experimental and theoretical uncertainties cancel in ratios of their cross-sections relative to minimum bias events. We explore such event engineering using the Color Glass Condensate (CGC) effective field theory to compute short distance charmonium cross-sections. The CGC is combined with heavy-quark fragmentation functions to compute $D$-meson cross-sections; for the $J/ψ$, hadronization is described e…

Simulations on the Heavy Hadron Transport at RHIC

Based on the hadron transport frames, detailed simulations are carried out to discuss $ϕ$, $Ω$ productions and the significant enhancements in the very low $p_T$ region for some of the soft spectra in RHIC. Elastic interactions are introduced in the simulations. The elastic cross sections vary from different hadrons and energy scales, which can qualitatively explain the different collective motions of various hadrons.

Propagation of heavy baryons in heavy-ion collisions

The drag and diffusion coefficients of heavy baryons ($Λ_c$ and $Λ_b$) in the hadronic phase created in the latter stage of the heavy-ion collisions at RHIC and LHC energies have been evaluated recently. In this work we compute some experimental observables, such as the nuclear suppression factor $R_{AA}$ and the elliptic flow $v_2$ of heavy baryons at RHIC and LHC energies, highlighting the role of the hadronic phase contribution to these observables, which are going to be measured at Run 3 of LHC. For the time evolution of the heavy quarks in the QGP and heavy baryons in the hadronic phase w…

Heavy quark production in photon - Pomeron interactions at hadronic colliders

The diffractive heavy quark cross sections are estimated considering photon-Pomeron ($γ\pom$) interactions in hadron - hadron at RHIC, Tevatron, and CERN LHC energies. We assume the validity of the hard diffractive factorization and calculate the charm and bottom total cross sections and rapidity distributions using the diffractive parton distribution functions of the Pomeron obtained by the H1 Collaboration at DESY-HERA. Moreover, we compare our predictions with those obtained using the dipole model. We verify that this process is a good test of the different mechanisms for diffractive heavy …

Multi-quark hadrons from Heavy Ion Collisions

Identifying hadronic molecular states and/or hadrons with multi-quark components either with or without exotic quantum numbers is a long standing challenge in hadronic physics. We suggest that studying the production of these hadrons in relativistic heavy ion collisions offer a promising resolution to this problem as yields of exotic hadrons are expected to be strongly affected by their structures. Using the coalescence model for hadron production, we find that compared to the case of a non-exotic hadron with normal quark numbers, the yield of an exotic hadron is typically an order of magnitud…

Hadronization and Charm-Hadron Ratios in Heavy-Ion Collisions

Understanding the hadronization of the quark-gluon plasma (QGP) remains a challenging problem in the study of strong-interaction matter as produced in ultrarelativistic heavy-ion collisions (URHICs). The large mass of heavy quarks renders them excellent tracers of the color neutralization process of the QGP when they convert into various heavy-flavor (HF) hadrons. We develop a 4-momentum conserving recombination model for HF mesons and baryons that recovers the thermal and chemical equilibrium limits and accounts for space-momentum correlations (SMCs) of heavy quarks with partons of the hydrod…

MARTINI for heavy quarks: initialization, parton evolution, and hadronization with event generation

We present additions to the MARTINI event generator for examining heavy quarks and quarkonia in heavy-ion collisions. All stages of a heavy-ion collision affect the observables associated with heavy quarks: the initial phase space of the heavy quarks are sampled with PYTHIA8.1, the heavy quarks are evolved using Langevin dynamics and a 3+1-dimensional hydrodynamical description of the heavy-ion collision, and are fragmented and hadronized using a modified version of the color evaporation model that takes into account non-trivial evolution in position space, as well as the possibility of recomb…

Hadronization Approach for a Quark-Gluon Plasma Formed in Relativistic Heavy Ion Collisions

A transport model is developed to describe hadron emission from a strongly coupled quark-gluon plasma formed in relativistic heavy ion collisions. The quark-gluon plasma is controlled by ideal hydrodynamics, and the hadron motion is characterized by a transport equation with loss and gain terms. The two sets of equations are coupled to each other, and the hadronization hypersurface is determined by both the hydrodynamic evolution and the hadron emission. The model is applied to calculate the transverse momentum distributions of mesons and baryons, and most of the results agree well with the ex…

Hadron Resonances and Phase Threshold in Heavy Ion Collisions

We show that a measurement of the reaction energy dependence of relative hadron resonance yields in heavy ion collisions can be used to study the phase structure of the dense QCD matter created in these collisions, and investigate the origin of the trends observed in the excitation functions of certain soft hadronic observables. We show that presence of chemical nonequilibrium in light quark abundance imparts a characteristic signature on the energy dependence of resonance yields, that differs considerably from what is expected in the equilibrium picture.

Explanation of hadron transverse-momentum spectra in heavy-ion collisions at sqrt(sNN) = 2.76 TeV within chemical non-equilibrium statistical hadronization model

Chemical non-equilibrium version of the statistical hadronization model combined with a single-freeze-out scenario is used to analyze the transverse-momentum spectra of pions, kaons and protons produced in heavy-ion collisions at sqrt(sNN) = 2.76 TeV. With the statistical parameters found in earlier studies of hadronic ratios and two new geometric parameters determined by the absolute normalization and slopes of the spectra, we obtain a very good agreement between the data and the model predictions. In particular, the enhancement of pions observed at the very low transverse-momenta is very wel…

Quenching of hadron and photon spectra in heavy-ion collisions from RHIC to LHC

The generic features of parton energy loss effects on the quenching of single hadron spectra in heavy-ion collisions are discussed, paying attention to the expected differences from RHIC to LHC. The need for precise baseline measurements in p-Pb collisions at the LHC is also emphasized. Finally I briefly mention the production of prompt photons in heavy-ion collisions as well as some open questions.

从pp到AA碰撞的重味强子化机制：理论视角

Heavy-flavor hadronization mechanism from pp to AA collisions: a theoretical perspective

本文从理论视角系统梳理了从pp到AA碰撞中重味强子化机制，强调其对提取夸克-胶子等离子体输运系数的重要性，并展示特定模型可自洽描述多个重味强子观测量。

Heavy Flavor and Jet Studies for the Future Electron-Ion Collider to Explore the Hadronization Process

Heavy flavor production at the future Electron-Ion Collider (EIC) will allow us to precisely determine the quark/gluon fragmentation processes in vacuum and the nuclear medium especially within the poorly constrained kinematic region. Heavy flavor hadron and jet reconstruction with the recent EIC detector design have been studies in simulation. Results of corresponding physics projections such as the flavor dependent hadron nuclear modification factor $R_{eA}$ in electron+nucleus collisions will be shown. The statistical precision obtained by these proposed heavy flavor measurements for the fu…