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Register a new userQuark number scaling of $p_{T}$ spectra for $Omega$ and $phi$ in relativistic heavy-ion collisions
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We show that the experimental data of transverse momentum ($p_{T}$) spectra of $Omega$ baryon and $phi$ meson at mid-rapidity in heavy-ion collisions exhibit the constituent quark number scaling in a wide energy range from RHIC to LHC. Such a scaling behavior is a direct consequence of quark combination mechanism via equal velocity combination and provides a very convenient way to extract the $p_{T}$ spectrum of strange quarks at hadronization. We present the results of strange quarks obtained from the available data and study the properties in particular the energy dependence of the averaged transverse momentum $langle p_{T}rangle$ and the transverse radial flow velocity $langlebetarangle$ with a hydrodynamics-motivated blast-wave model.
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We have studied elliptic flow ($v_{2}$) of $phi$-mesons in the framework of a multi phase transport (AMPT) model at LHC energy. In the realms of AMPT model we observe $phi$-mesons at intermediate transverse momentum ($p_{T}$) deviate from the previously observed (at RHIC) particle type grouping of $v_{2}$ according to the number of quark content i.e, baryons and mesons. Recent results from the ALICE Collaboration have shown that $phi$-meson and proton $v_{2}$ has a similar trend, possibly indicating that particle type grouping might be due to the mass of the particles and not the quark content. A stronger radial boost at LHC compared to RHIC seems to offer a consistent explanation to such observation. However, recalling that $phi$-mesons decouple from the hadronic medium before additional radial flow is build-up in the hadronic phase, similar pattern in $phi$-meson and proton $v_{2}$ may not be due to radial flow alone. Our study reveals that models incorporating $phi$-meson production from $Kbar{K}$ fusion in the hadronic rescattering phase also predict a comparable magnitude of $phi$-meson and proton $v_{2}$ particularly in the intermediate region of $p_{T}$. Whereas, $v_{2}$ of $phi$-mesons created in the partonic phase is in agreement with quark-coalescence motivated baryon-meson grouping of hadron $v_{2}$. This observation seems to provide a plausible alternative interpretation for the apparent mass-like behaviour of $phi$-meson $v_{2}$. We have also observed a violation of hydrodynamical mass ordering between proton and $phi$-meson $v_{2}$ further supporting that $phi$-mesons are negligibly affected by the collective radial flow in the hadronic phase due to the small in-medium hadronic interaction cross sections.
The $Delta$-scaling method has been applied to the total multiplicity distribution of the relativistic ion collisions of p+p, C+C and Pb+Pb which were simulated by a Monte Carlo package, LUCIAE 3.0. It is found that the $Delta$-scaling parameter decreases with the increasing of the system size. Moreover, the heat capacities of different mesons and baryons have been extracted from the event-by-event temperature fluctuation in the region of low transverse mass and they show the dropping trend with the increasing of impact parameter.
A systematic analysis of correlations between different orders of $p_T$-differential flow is presented, including mode coupling effects in flow vectors, correlations between flow angles (a.k.a. event-plane correlations), and correlations between flow magnitudes, all of which were previously studied with integrated flows. We find that the mode coupling effects among differential flows largely mirror those among the corresponding integrated flows, except at small transverse momenta where mode coupling contributions are small. For the fourth- and fifth-order flow vectors $V_4$ and $V_5$ we argue that the event plane correlations can be understood as the ratio between the mode coupling contributions to these flows and and the flow magnitudes. We also find that for $V_4$ and $V_5$ the linear response contribution scales linearly with the corresponding cumulant-defined eccentricities but not with the standard eccentricities.
A QCD phase transition may reflect in a inhomogeneous decoupling surface of hadrons produced in relativistic heavy-ion collisions. We show that due to the non-linear dependence of the particle densities on the temperature and baryon-chemical potential such inhomogeneities should be visible even in the integrated, inclusive abundances. We analyze experimental data from Pb+Pb collisions at CERN-SPS and Au+Au collisions at BNL-RHIC to determine the amplitude of inhomogeneities.
We study the single electron spectra from $D-$ and $B-$meson semileptonic decays in Au+Au collisions at $sqrt{s_{rm NN}}=$200, 62.4, and 19.2 GeV by employing the parton-hadron-string dynamics (PHSD) transport approach that has been shown to reasonably describe the charm dynamics at RHIC and LHC energies on a microscopic level. In this approach the initial heavy quarks are produced by using the PYTHIA which is tuned to reproduce the FONLL calculations. The produced heavy quarks interact with off-shell massive partons in QGP with scattering cross sections which are calculated in the dynamical quasi-particle model (DQPM). At energy densities close to the critical energy density the heavy quarks are hadronized into heavy mesons through either coalescence or fragmentation. After hadronization the heavy mesons interact with the light hadrons by employing the scattering cross sections from an effective Lagrangian. The final heavy mesons then produce single electrons through semileptonic decay. We find that the PHSD approach well describes the nuclear modification factor $R_{rm AA}$ and elliptic flow $v_2$ of single electrons in d+Au and Au+Au collisions at $sqrt{s_{rm NN}}=$ 200 GeV and the elliptic flow in Au+Au reactions at $sqrt{s_{rm NN}}=$ 62.4 GeV from the PHENIX collaboration, however, the large $R_{rm AA}$ at $sqrt{s_{rm NN}}=$ 62.4 GeV is not described at all. Furthermore, we make predictions for the $R_{rm AA}$ of $D-$mesons and of single electrons at the lower energy of $sqrt{s_{rm NN}}=$ 19.2 GeV. Additionally, the medium modification of the azimuthal angle $phi$ between a heavy quark and a heavy antiquark is studied. We find that the transverse flow enhances the azimuthal angular distributions close to $phi=$ 0 because the heavy flavors strongly interact with nuclear medium in relativistic heavy-ion collisions and almost flow with the bulk matter.
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