We study the production of $ΛΛ$ and $\overline{Λ\text{n}}$ exotic states in central Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV at LHC via both hadron and quark coalescence within a covariant coalescence model with a blast-wave-like parametrization for the phase-space configurations of constituent particles at freezeout. In the hadron coalescence, the two states are considered as molecular states while they are considered as six-quark states in the quark coalescence.For $\overline{Λ\text{n}}$, we find that the yields of both molecular and six-quark states are much larger than the experimental upper-limits. For $ΛΛ$, while the molecule-state yield is much larger than the experimental upper-limits, the six-quark-state yield could be lower than the upper-limits. The higher molecule-state yields are mainly due to the large contribution of short-lived strong resonance decays into (anti-)nucleons and (anti-)$Λ$ which can significantly enhance the molecule-state yields of $ΛΛ$ and $\overline{Λ\text{n}}$ via hadron coalescence. Our results suggest that the current experimental measurement at LHC cannot exclude the existence of the $ΛΛ$ as an exotic six-quark state, and if $ΛΛ$ is a six-quark state, it is then on the brink of being discovered.
Using a covariant quark coalescence model combined with a blast-wave-like analytical parametrization for (anti-)strange quark phase-space freeze-out configuration, we extract information on strange quark freeze-out dynamics in Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV by fitting the measured transverse momentum spectra and elliptic flows ($v_2$) of $ϕ$ mesons and $Ω$ baryons. We find that although both the measured and calculated $v_2$ of $ϕ$ and $Ω$ satisfy the number-of-constituent-quark (NCQ) scaling, the NCQ-scaled $v_2$ is significantly smaller than the $v_2$ of strange quarks, implyin…
Elliptic flow of hadrons observed at relativistic heavy-ion collision experiments at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC), provides us an important signature of possible de-confinement transition from hadronic phase to partonic phase. However, hadronization processes of de-confined partons back into final hadrons are found to play a vital role in the observed hadronic flow. In the present work, we use coalescence mechanism also known as Recombination (ReCo) to combine quarks into hadrons. To get there, we have used Boltzmann transport equation in relaxation ti…
We investigate the role of partonic degrees of freedom in high multiplicity p-Pb collisions at $\sqrt{s_{NN}}=$ 5.02 TeV carried out at the Large Hadron Collider (LHC) by studying the production and collective flow of identified hadrons at intermediate $p_T$ via the coalescence of soft and hard partons generated from viscous hydrodynamics (VISH2+1) and the energy loss model (LBT), respectively. We find that combining the intermediate $p_T$ hadrons from the coalescence with the low $p_T$ hadrons from hydrodynamics and high $p_T$ hadrons from the jet fragmentation, our Hydro-Coal-Frag model prov…
We briefly summarize our recent study on the number of constituent quark (NCQ) scaling of hadron elliptic flows in high multiplicity p-Pb collisions at $\sqrt{s_{NN}}=$ 5.02 TeV. With the inclusion of hadron production via the quark coalescence model at intermediate $p_T$, the viscous hydrodynamics at low $p_T$, and jet fragmentation at high $p_T$, our $Hydro-Coal-Frag$ model provides a nice description of the $p_T$-spectra and differential elliptic flow $v_2(p_T)$ of pions, kaons and protons over the $p_T$ range from 0 to 6 GeV. Our results demonstrate that including the quark coalescence is …
Based on a covariant coalescence model with a blast-wave-like parametrization for the phase-space configuration of constituent particles at freeze-out, we derive an approximate analytical formula for the yields of clusters produced in relativistic heavy-ion collisions. Compared to previous existing formulae, the present work additionally considers the contributions from the longitudinal dimension in momentum space, the relativistic corrections and the finite size effects of the produced clusters relative to the spatial distribution of constituent particles at freeze-out. The new analytical coa…
A study of elliptic flow of open charm mesons, $D^0$ and $D_S ^\pm$ using quark coalescence as a mechanism of hadronization of heavy quarks implemented in conjunction with A Multi Phase Transport (AMPT) model has been presented. We have studied the transverse momentum dependence of the elliptic flow parameter at mid-rapidity ($|y|$ $<$ 1.0) for Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV (RHIC) and Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV (LHC) for different values of partonic interaction cross-section and QCD coupling constant. We have compared our calculations with the experimentally…
Using the coalescence model based on the phase-space distribution of nucleons from an extended blast-wave model that includes the space-momentum correlation of high momentum nucleons, we study the transverse momentum spectra and elliptic flows of deuteron and helium-3 in Pb+Pb collisions at the energy $\sqrt{s_{NN}}=2.76$ TeV. We find that the measured elliptic flows of deuteron can be satisfactorily described if nucleons of large transverse momenta are more spread in space when their momenta are more aligned along the reaction plane.
The string melting version of a multi-phase transport model is often applied to high-energy heavy-ion collisions since the dense matter thus formed is expected to be in parton degrees of freedom. In this work we improve its quark coalescence component, which describes the hadronization of the partonic matter to a hadronic matter. We removed the previous constraint that forced the numbers of mesons, baryons, and antibaryons in an event to be separately conserved through the quark coalescence process. A quark now could form either a meson or a baryon depending on the distance to its coalescence …
Technical University of Munich（慕尼黑工业大学）；Thomas Jefferson National Accelerator Facility（托马斯·杰斐逊国家加速器设施）；INFN Pisa（意大利国家核物理研究所比萨分部）；Università di Bologna（博洛尼亚大学）；Università di Pisa（比萨大学）
We introduce additional coalescence factors for the production of strange baryons in a multiphase transport (AMPT) model in order to describe the enhanced production of multistrange hadrons observed in Pb-Pb collisions at $\rm \sqrt{s_{NN}}$ = 2.76 TeV at the Large hadron Collider (LHC) and Au+Au collisions at $\rm \sqrt{s_{NN}}$ = 200 GeV at Relativistic Heavy-Ion Collider (RHIC).This extended AMPT model is found to also give a reasonable description of the multiplicity dependence of the strangeness enhancement observed in high multiplicity events in $pp$ collisions at $\rm \sqrt{s}$ = 7 TeV …
We extend our earlier study on two-particle angular correlations in $pp$ collisions at low transverse momentum ($p_T$) to $p$-Pb, Pb-Pb and Au-Au collisions at RHIC and LHC energies. We mainly use the string melting version of a multiphase transport model with improved quark coalescence for this study. We start from the analysis of $π^{\pm}$, $K^{\pm}$ and $p$($\bar{p}$) $p_T$ and rapidity distributions at different centralities. We then focus on two-particle angular correlations in $p$-Pb collisions at $\mathrm{\sqrt{s_{NN}} = 5.02}$ TeV and Pb-Pb collisions at $\mathrm{\sqrt{s_{NN}}= 2.76}$ …
Coalescence has long been used to describe the production of light (anti-)nuclei in heavy ion collisions. The same underlying mechanism may also exist in jets when a proton and a neutron are close enough in phase space to form a deuteron. We model deuteron production in jets by applying an afterburner to protons and neutrons produced in PYTHIA for $p$+$p$ collisions at a center of mass energy $\sqrt{s} =$ 7 TeV. PYTHIA provides a reasonable description of the proton spectra and the shape of the deuteron spectrum predicted by the afterburner is in agreement with the data. We show that the rise …
We study the $J/ψ$ production based on coalescence model at $\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV Pb-Pb collisions. With the colliding energy increasing from 2.76 TeV to 5.02 TeV, the number of charm pairs is enhanced by more than 50%. However, the ratio of $J/ψ$ inclusive nuclear modification factors $R^{5.02TeV}_{AA}/R^{2.76TeV}_{AA}$ is only about 1.1 $\sim$ 1.2. We find that the regeneration of $J/ψ$ is proportional to the densities of charm and anti-charm quarks, instead of their total numbers. The charm quark density is diluted by the strong expansion of quark gluon plasma, which suppresse…
Studies of beauty hadron and non-prompt charm hadron production in pp collisions at $\sqrt{s}$=13 TeV within a transport model approach
School of Mathematics and Physics, China University of Geosciences (Wuhan)（中国地质大学（武汉）数学与统计学院）；Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University（华中师范大学夸克与轻子物理教育部重点实验室及粒子物理研究所）；Shanghai Research Center for Theoretical Nuclear Physics, NSFC and Fudan University（复旦大学理论核物理上海研究中心）
We resolve the difference in the yield ratio $\rm S_3$ = $\rm \frac{N_{^3_ΛH}/N_Λ}{N_{^3He}/N_p}$ measured in Au+Au collisions at $\rm \sqrt{s_{NN}}$ = 200 GeV and in Pb-Pb collisions at $\rm \sqrt{s_{NN}}$ = 2.76 TeV by adopting a different treatment of the weak decay contribution to the proton yield in Au+Au collisions at $\rm \sqrt{s_{NN}}$ = 200 GeV. We then use the coalescence model to extract information on the $Λ$ and nucleon density fluctuations at the kinetic freeze-out of heavy ion collisions. We also show from available experimental data that the yield ratio $\rm S_2$ = $\rm \frac{N…
Production of light (anti-)nuclei and (anti-)hypertriton within midrapidity ($|y|<0.5$) and $p_T<3.0$ GeV/c in $pp$ interactions at $\sqrt{s}$ = 0.90, 2.76 and 7 TeV is investigated by the dynamically constrained phase space coalescence model (DCPC), combined with {\footnotesize{PACIAE}} model. The ALICE data for yields, ratios, as well as transverse momentum distributions of $\overline{d}$ and $d$ are well reproduced by the model simulations, meanwhile the three basic characters of $\rm^3{\overline{He}}$, $\rm^3{He}$, $\rm{{^3_{\overline Λ}\overline H}}$, and $\rm{^3_ΛH}$ are also predicted. …
In this paper, we study and predict the charged-particle pseudorapidity multiplicity density ($\frac{dN_{ch}}{dη}$), transverse momentum spectra of identified particles and their ratios in relativistic heavy ion collisions at the Large Hadron Collider (LHC), using the string-melting version of a multi-phase transport (AMPT) model with improved quark coalescence method. Results of the charged-particle pseudorapidity multiplicity density from AMPT model calculations for Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are compared with the experimental data. Good agreements are generally found betwe…
Macroscopic study of $ϕ$-mesic nuclei in $pp$ collisions at $\sqrt{s}$ = 7 TeV with the PACIAE model
Central China Normal University（华中师范大学）；Wuhan Textile University（武汉纺织大学）；Guizhou Normal University（贵州师范大学）；Shaanxi Normal University（陕西师范大学）；Sichuan University（四川大学）；China Institute of Atomic Energy（中国原子能科学研究院）；Nanjing University of Aeronautics and Astronautics（南京航空航天大学）
We study the $B_c^+$ production in Pb-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. In the quark-gluon plasma (QGP) produced in heavy-ion collisions, heavy quarks make random motions with the energy loss. We employ the Langevin equations to study the non-equilibrium distributions of heavy quarks and the Instantaneous Coalescence Model (ICM) to study the hadronization process. Due to abundant charm and bottom quarks in the QGP, their coalescence probability is significantly enhanced compared with the situations in proton-proton collisions. We find that the final production of $B_c^+$ is increased …
Xe+Xe collisions at relativistic energies provide us with an opportunity to study a possible system with deconfined quarks and gluons, whose size is in between those produced by p+p and Pb+Pb collisions. In the present work, we have used AMPT transport model with nuclear deformation to study the identified particle production such as ($π^{+}+π^{-}$), (K$^{+}$+K$^{-}$), $\rm{K}_{s}^0$, (p+$\bar{\rm{p}}$), $ϕ$ and ($Λ+ \barΛ$) in Xe+Xe collisions at $\sqrt{s_{\rm NN}}$=5.44 TeV. We study the $p\rm{_T}$-spectra, integrated yield, $p\rm{_T}$-differential and $p\rm{_T}$-integrated particle ratios t…
Even though lots of $Λ$-hypernuclei have been found and measured, multi-strangeness hypernuclei consisting of $Ω$ are not yet discovered. The studies of multi-strangeness hypernuclei help us further understand the interaction between hyperons and nucleons. Recently the $ΩN$ and $ΩΩ$ interactions as well as binding energies were calculated by the HAL-QCD's lattice Quantum Chromo-Dynamics (LQCD) simulations and production rates of $Ω$-dibaryon in Au + Au collisions at RHIC and Pb + Pb collisions at LHC energies were estimated by a coalescence model. The present work discusses the production of m…
We apply a multi-phase transport (AMPT) model to study two-particle angular correlations in $pp$ collisions at $\sqrt{s}= 7$ TeV. Besides being able to describe the angular correlation functions of meson-meson pairs, a large improvement for the angular correlations of baryon-baryon and antibaryon-antibaryon is achieved. We further find that the AMPT model with new quark coalescence provides an even better description on the anti-correlation feature of baryon-baryon correlations observed in the experiments. We also extend the study to p-Pb collisions at $\sqrt{s}= 5.02$ TeV and obtained similar…
The nuclear modification factors ($R_{AA}$) of $π^{\pm}, p(\bar p)$, and $d(\bar d)$ with $|y|<0.5, p_T<20.0$~GeV/c in peripheral (40-60\%) and central (0-5\%) Pb-Pb collisions at $\sqrt {s_{NN}}=2.76$ TeV have been studied using the parton and hadron cascade ({\footnotesize PACIAE}) model plus the dynamically constrained phase space coalescence ({\footnotesize DCPC}) model. It is found that the $R_{AA}$ of light (anti)nuclei ($d, \bar d$) is similar to that of hadrons ($π^\pm, p, \bar p$), and the $R_{AA}$ of antiparticles is the same as that of particles. The suppression of $R_{AA}$ at high-…
The deuteron binding energy is only 2.2 MeV. At the same time, its yield in Pb+Pb collisions at $\sqrt{s_{NN}} = $2.76 TeV corresponds to a thermal yield at the temperature around 155 MeV, which is too hot to keep deuterons bound. This puzzle is not completely resolved yet. In general, the mechanism of light nuclei production in ultra-high energy heavy ion collisions remains under debate. In a previous work [1] we suggest a microscopic explanation of the deuteron production in central ultra-relativistic Pb+Pb collisions, the main mechanism being $πpn \leftrightarrow πd$ reactions in the hadron…
Anisotropic Flow of light (anti-)(hyper-)nuclei in Pb+Pb Collision at $\sqrt{s_{NN}}=5.36$ TeV
Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Fudan University（复旦大学现代物理研究所）；Shanghai Research Center for Theoretical Nuclear Physics, NSFC and Fudan University（复旦大学理论核物理上海研究中心）；School of Nuclear Science and Technology, University of Chinese Academy of Sciences（中国科学院大学核科学与技术学院）；Heavy lon Science and Technology Key Laboratory, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所重离子科学和技术重点实验室）；Cyclotron Institute and Department of Physics and Astronomy, Texas A&M University（德州农工大学回旋加速器研究所及物理与天文学系）；School of Physics, East China Normal University（华东师范大学物理系）
The mass ordering of $v_{2}^{hadron}$ is regarded as one of the key signatures of collective behaviour in ultra relativistic heavy ion collisions. This observation has been found to be in compliance with the hydrodynamical response of a strongly interacting system to the initial spatial anisotropy. Flow co-efficients measured with identified particles in p-Pb/d-Au collisions have shown similar mass-splitting of $v_{2}^{hadron}$ indicating towards the presence of collective dynamics in small collision systems. Arguably, small size in the overlap geometry of such colliding systems may not be sui…
We show that the measured yield ratio $^3_Λ$H/$^3$He ($^3_{\overlineΛ}\overline{\text{H}}$/$^3\overline{\text{He}}$) in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV and in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV can be understood within a covariant coalescence model if (anti-)$Λ$ particles freeze out earlier than (anti-)nucleons but their relative freezeout time is closer at $\sqrt{s_{NN}}=2.76$ TeV than at $\sqrt{s_{NN}}=200$ GeV. The earlier (anti-)$Λ$ freezeout can significantly enhance the yield of (anti)hypernucleus $^4_Λ$H ($^4_{\overlineΛ}\overline{\text{H}}$), leading to that $^4_{…
A Linearized Boltzmann Transport (LBT) model coupled with hydrodynamical background is established to describe the evolution of jet shower partons and medium excitations in high energy heavy-ion collisions. We extend the LBT model to include both elastic and inelastic processes for light and heavy partons in the quark-gluon plasma. A hybrid model of fragmentation and coalescence is developed for the hadronization of heavy quarks. Within this framework, we investigate how heavy flavor observables depend on various ingredients, such as different energy loss and hadronization mechanisms, the mome…
Within the ultra-relativistic quantum molecular dynamics (UrQMD) model, in which the Lorentz-covariant treatment of nuclear mean-field potential is considered, the fluctuations of net-baryon, net-charge and deuterons multiplicity distributions in Au+Au head-on collisions at $\sqrt{s_{NN}}=3.0-5.0$ GeV are calculated. The results show that the nuclear mean-field potential can significantly enhance the magnitude of baryon number fluctuations in narrow rapidity windows, and this enhancement rapidly weakens with increasing beam energy. However, for proton and net-charge number fluctuations, the me…
Within the framework of the coalescence model based on the phase-space distributions of protons and neutrons generated from the {\tt iEBE-VISHNU} hybrid model with {\tt AMPT} initial conditions, we study the spectra and elliptic flow of deuterons and helium-3 in relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Larger Hadron Collider (LHC). Results from our model calculations for Au + Au collisions at $\sqrt{s_{NN}}=200$ GeV at RHIC and Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV at the LHC are compared with available experimental data. Good agreements ar…
Using the nucleon coalescence model based on kinetic freeze-out nucleons from the 3D MUSIC+UrQMD and the 2D VISHNU hybrid model with a crossover equation of state, we study the multiplicity dependence of deuteron ($d$) and triton ($t$) production from central to peripheral Au+Au collisions at $\sqrt{s_\mathrm{NN}}=$ 7.7, 14.5, 19.6, 27, 39, 62.4 and 200 GeV and Pb+Pb at $\sqrt{s_\mathrm{NN}}=2.76$ TeV, respectively. It is found that the ratio $N_t N_p/N_d^2$ of the proton yield $N_p$, deuteron yield $N_d$ and triton yield $N_t$ exhibits a scaling behavior in its multiplicity dependence, i.e., …
We investigate the effects of (2+1)d event-by-event fluctuating hydrodynamic backgrounds on the nuclear modification factor and momentum anisotropies of heavy-flavor mesons. Using the state-of-the-art D and B mesons modular simulation code (the so-called DAB-mod), updated recently with heavy-light quark coalescence, we perform a systematic comparison of different transport equations, including two energy loss models and a relativistic Langevin model with two drag parametrizations. We present the resulting D$^0$ meson $R_{AA}$, $v_2$ and $v_3$, using the multiparticle cumulant method, in Pb-Pb …
