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Register a new userCharmed hadron chemistry in relativistic heavy-ion collisions
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We develop for charmed hadron production in relativistic heavy-ion collisions a comprehensive coalescence model that includes an extensive set of $s$ and $p$-wave hadronic states as well as the strict energy-momentum conservation, which ensures the boost invariance of the coalescence probability and the thermal limit of the produced hadron spectrum. By combining our hadronization scheme with an advanced Langevin-hydrodynamics model that incorporates both elastic and inelastic energy loss of heavy quarks inside the dynamical quark-gluon plasma, we obtain a successful description of the $p_mathrm{T}$-integrated and differential $Lambda_c/D^0$ and $D_s/D^0$ ratios measured at RHIC and the LHC. We find that including the effect of radial flow of the medium is essential for describing the enhanced $Lambda_c/D^0$ ratio observed in relativistic heavy-ion collisions. We also find that the puzzling larger $Lambda_c/D^0$ ratio observed in Au+Au collisions at RHIC than in Pb+Pb collisions at the LHC is due to the interplay between the effects of the QGP radial flow and the charm quark transverse momentum spectrum at hadronization. Our study further suggests that charmed hadrons have larger sizes in medium than in vacuum.
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We investigate the $LambdaLambda$ and $K^-p$ intensity correlations in high-energy heavy-ion collisions. First, we examine the dependence of the $LambdaLambda$ correlation on the $LambdaLambda$ interaction and the $LambdaLambda$ pair purity probability $lambda$. For small $lambda$, the correlation function needs to be suppressed by the $LambdaLambda$ interaction in order to explain the recently measured $LambdaLambda$ correlation data. By comparison, when we adopt the $lambda$ value evaluated from the experimentally measured $Sigma^0/Lambda$ ratio, the correlation function needs to be enhanced by the interaction. We demonstrate that these two cases correspond to the two analyses which gave opposite signs of the $LambdaLambda$ scattering length. Next, we discuss the $K^-p$ correlation function. By using the local $bar{K}N$ potential which reproduces the kaonic hydrogen data by SIDDHARTA, we obtain the $K^-p$ correlation function. We find that the $K^-p$ correlation can provide a complementary information with the $K^{-}p$ elastic scattering amplitude.
Based on a generalized side-jump formalism for massless chiral fermions, which naturally takes into account the spin-orbit coupling in the scattering of two chiral fermions and the chiral vortical effect in a rotating chiral fermion matter, we have developed a covariant and total angular momentum conserved chiral transport model to study both the global and local polarizations of this matter. For a system of massless quarks of random spin orientations and finite vorticity in a box, we have demonstrated that the model can exactly conserve the total angular momentum of the system and dynamically generate the quark spin polarization expected from a thermally equilibrated quark matter. Using this model to study the spin polarization in relativistic heavy-ion collision, we have found that the local quark spin polarizations depend strongly on the reference frame where they are evaluated as a result of the nontrivial axial charge distribution caused by the chiral vortical effect. We have further shown that because of the anomalous orbital or side-jump contribution to the quark spin polarization, the local quark polarizations calculated in the medium rest frame are qualitatively consistent with the local polarizations of Lambda hyperons measured in experiments.
We study the production of multi-charmed hadrons by recombination in heavy ion collisions by focusing on the production of $Xi_{cc}$, $Xi_{cc}^*$, $Omega_{scc}$, $Omega_{scc}^*$, $Omega_{ccc}$ 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 $Xi_{cc}$ but also those which have not been observed yet, can be discovered sufficiently in heavy ion collisions. We also find that the transverse momentum distribution ratio between various multi-charmed hadrons sensitively reflects the interplay between quark contents of corresponding hadrons as well as the transverse momentum distribution of charm quarks at the hadronization point, and therefore we insist that studying both the transverse momentum distributions of multi-charmed hadrons themselves and transverse momentum distribution ratios between various multi-charmed hadrons provide us with useful information on hadron production mechanism involving charm quarks 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 hydrodynamically expanding QGP, thereby resolving a long-standing problem in quark coalescence models. The SMCs enhance the recombination of fast-moving heavy quarks with high-flow thermal quarks in the outer regions of the fireball. We also improve the hadro-chemistry with missing charm-baryon states, previously found to describe the large $Lambda_c/D^0$ ratio observed in proton-proton collisions. Both SMCs and hadro-chemistry, as part of our HF hydro-Langevin-recombination model for the strongly coupled QGP, importantly figure in the description of recent data for the $Lambda_c/D^0$ ratio and $D$-meson elliptic flow in URHICs.
We develop a combined hydro-kinetic approach which incorporates a hydrodynamical expansion of the systems formed in textit{A}+textit{A} collisions and their dynamical decoupling described by escape probabilities. The method corresponds to a generalized relaxation time ($tau_{text{rel}}$) approximation for the Boltzmann equation applied to inhomogeneous expanding systems; at small $tau_{text{rel}}$ it also allows one to catch the viscous effects in hadronic component - hadron-resonance gas. We demonstrate how the approximation of sudden freeze-out can be obtained within this dynamical picture of continuous emission and find that hypersurfaces, corresponding to a sharp freeze-out limit, are momentum dependent. The pion $m_{T}$ spectra are computed in the developed hydro-kinetic model, and compared with those obtained from ideal hydrodynamics with the Cooper-Frye isothermal prescription. Our results indicate that there does not exist a universal freeze-out temperature for pions with different momenta, and support an earlier decoupling of higher $p_{T}$ particles. By performing numerical simulations for various initial conditions and equations of state we identify several characteristic features of the bulk QCD matter evolution preferred in view of the current analysis of heavy ion collisions at RHIC energies.
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