The Chiral Magnetic Effect (CME) is predicted for mid-peripheral Au-Au collisions $\sqrt{s_{NN}}$=200 GeV at RHIC. However many backgrounds can give signals that make the measurement hard to interpret. The STAR experiment has made a measurement that makes it possible to separate out the background from the signal. An event shape analysis is the key for controlling the effects of Transverse Momentum Conservation (TMC) in the Au-Au collisions. LHC Pb-Pb collision $\sqrt{s_{NN}}$=2.76 TeV has made event plane measurements from which we calculate the CME and make predictions about what the event shape analysis should give.
The charge density distribution with respect to the velocity of matter produced in peripheral heavy ion reactions around Fermi energy is investigated. The experimental finding of enhancement of mid-rapidity matter shows the necessity to include correlations beyond BUU which was performed in the framework of nonlocal kinetic theory. Different theoretical improvements are discussed. While the in-medium cross section changes the number of collisions, it leaves the transferred energy almost unchanged. In contrast the nonlocal scenario changes the energy transferred during collisions and leads to a…
High energy ultra-peripheral collisions (UPC) of heavy-ions generate strong electromagnetic fields which open the possibility to study gamma-gamma and gamma-nucleus processes in a kinematic regime so far unexplored. We report on preliminary PHENIX results of J/Psi and high-mass e+e- photoproduction at mid-rapidity in coherent electromagnetic Au+Au interactions at sqrt(s_NN) = 200 GeV tagged with forward neutron emission from the Au* dissociation.
In this paper we will show that one can summarize the major two particle reaction plane azimuthal correlations for Au + Au mid-central collisions at $\sqrt{s_{NN}} =$ 200 GeV by defining a 2D azimuthal space which is a summary of the event by event average.
There exist several proposals to use Weizsäcker-Williams photons generated by ultrarelativistic heavy ions to produce exotic particles in $γγ$ fusion reactions. To estimate the background conditions for such reactions we analyze various mechanisms of meson production in very peripheral collisions of ultrarelativistic heavy ions at RHIC and LHC energies. Besides $γγ$ fusion they include also electromagnetic $γA$ interactions and strong nucleon-nucleon interactions in grazing $AA$ collisions. All these processes are characterised by low multiplicities of produced particles. $γA$ and $AA$ events …
We have developed a relativistic kinetic transport approach that incorporates initial state fluctuations allowing to study the build up of elliptic flow $v_2$ and high order harmonics $v_3$, $v_4$ and $v_5$ for a fluid at fixed $η/s(T)$. We study the effect of the $η/s$ ratio and its T dependence on the build up of the $v_n(p_T)$ for two different beam energies: RHIC for Au+Au at $\sqrt{s}=200 \,GeV$ and LHC for $Pb+Pb$ at $\sqrt{s}=2.76 \,TeV$. We find that for the two different beam energies considered the suppression of the $v_n(p_T)$ due to the viscosity of the medium have different contri…
We present a detailed study of isospin dynamics in peripheral collisions at Fermi energies. We consider symmetric and mixed collisions of (124,112)Sn isotopes at 35 and 50 AMeV to study the isospin transport between the different reaction components (residues, gas and possibly intermediate mass fragments) and, in particular, the charge equilibration in the mixed system. We evaluate the effects of drift terms due to asymmetry and density gradients, which are directly related to the poorly known value and slope of the symmetry energy below saturation density. We verify the importance of an isosc…
In this paper, we use a multi-phase transport model to simulate the parton evolution time-dependent transverse asymmetry in peripheral Pb-Pb (b=14-15 fm) and p-Pb (b=0-1 fm) collisions at $\sqrt{s_{NN}}$= 5.02 TeV, respectively. The simulated results showed that the initial spatial asymmetry depends on the collision system, while both the initial momentum asymmetry and final momentum asymmetry are independent on the collision system. It is also shown that the final momentum asymmetry is similar to the initial momentum asymmetry. Furthermore, the averaged transverse shape asymmetry, which inclu…
The transverse momentum distribution of produced charged particles is investigated for gold-gold collisions at $\sqrt{s_{NN}}=200$ GeV. A simple parameterization is suggested for the particle distribution based on the nuclear stopping effect. The model can fit very well both the transverse momentum distributions at different pseudo-rapidities and the pseudo-rapidity distributions at different centralities. The ratio of rapidity distributions for peripheral and central collisions is calculated and compared with the data.
The dynamical development of collective flow is studied in a (3+1)D fluid dynamical model, with globally symmetric, peripheral initial conditions, which take into account the shear flow caused by the forward motion on the projectile side and the backward motion on the target side. While at $\sqrt{s_{NN}} = 2.76A$\,TeV semi-peripheral Pb+Pb collisions the earlier predicted rotation effect is visible, at more peripheral collisions, with high resolution and low numerical viscosity the initial development of a Kelvin-Helmholtz instability is observed, which alters the flow pattern considerably. Th…
We provide the first calculation of two-gluon production at mid-rapidity in ultra-peripheral collisions in the Color Glass Condensate framework. To estimate systematic uncertainty associated with poor understanding of the wave function of the nearly real photon, we consider two diametrically different models: the dilute quark-antiquark dipole approximation and a vector meson, in which color charge density is approximated by McLerran-Venugopalan model. In the experimentally relevant range, the target nucleus can be faithfully approximated by a highly saturated state. This simplification enables…
We calculate the centrality dependence of direct photons produced in Au+Au collisions at sqrt{s}=200GeV and their transverse momentum spectra within the Parton-Hadron-String Dynamics (PHSD) transport approach. As sources for 'direct' photons, we incorporate the interactions of quarks and gluons as well as hadronic interactions (pi+pi->rho+gamma, rho+pi->pi+gamma, meson-meson bremsstrahlung m+m->m+m+gamma, meson-baryon bremsstrahlung m+B->m+B+gamma), the decays of phi and a_1 mesons and the photons produced in the initial hard collisions ('pQCD'). We find that the pT spectra of the 'thermal' ph…
We investigate the squeezed back-to-back correlations (BBC) of $K^+$$K^-$, caused by the mass modification of the particle in the dense medium formed in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV and Au+Au collisions at $\sqrt{s_{NN}}=62.4$ GeV. Considering some kaons may be not affected by the medium, we further study the BBC functions of $K^+$$K^-$ when parts of all kaons have a mass-shift. Our results indicate that the BBC functions of $K^+$$K^-$ can be observed when only about 10$\%$ of all kaons have a mass-shift in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV and the peripheral collisions …
Transverse momentum spectra of different types of particles produced in mid-rapidity interval in central and peripheral gold-gold (Au-Au) collisions, central and peripheral deuteron-gold ($d$-Au) collisions, and inelastic (INEL) or non-single-diffractive (NSD) proton-proton ($pp$) collisions at the Relativistic Heavy Ion Collider (RHIC), as well as in central and peripheral lead-lead (Pb-Pb) collisions, central and peripheral proton-lead ($p$-Pb) collisions, and INEL or NSD $pp$ collisions at the Large Hadron Collider (LHC) are analyzed by the blast-wave model with Boltzmann-Gibbs statistics. …
We have studied the centrality dependence of charged particle forward-backward multiplicity correlation strength in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV with a parton and hadron cascade model, PACIAE, based on PYTHIA. The calculated results are compared with the STAR data. The experimentally observed correlation strength characters: (1) the approximately flat pseudorapidity dependence in central collisions and (2) the monotonous decrease with decreasing centrality are well reproduced. However the theoretical results are bigger than the STAR data for the peripheral collisions. A discussi…
The impact parameter dependence of \rpi ratio is examined in heavy-ion collisions at 400MeV/nucleon within a transport model. It is shown that the sensitivity of \rpi ratio on symmetry energy shows a transition from central to peripheral collisions, i.e., the stiffer symmetry energy leads to a larger \rpi ratio in peripheral collisions while the softer symmetry energy always leads this ratio to be larger in central collisions. After checking the kinematic energy distribution of \rpi ratio, we found this transition of sensitivity of \rpi ratio to symmetry energy is mainly from less energetic pi…
Centrality dependence of charged particles multiplicity, transverse momentum spectra, integrated and differential elliptic flow, in $\sqrt{s}_{NN}$=200 GeV Au+Au collisions are analyzed using event by event ideal hydrodynamics. Monte-Carlo Glauber model of initial condition, constrained to reproduce experimental charged particle's multiplicity in 0-10% Au+Au collisions, reasonably well reproduces all the experimental observables, e.g. centrality dependence of charged particles multiplicity, integrated and differential elliptic flow. Model predictions for higher flow harmonics, $v_3$, $v_4$ how…
We study the effect of spatially homogeneous and inhomogeneous shadowing on $J/ψ$ production in deuterium-nucleus collisions. We discuss how the shadowing and its spatial dependence may be measured by comparing central and peripheral $dA$ collisions. These event classes may be selected by using gray protons from heavy ion breakup and events where the proton or neutron in the deuterium does not interact. We find that inhomogenous shadowing has a significant effect on central $dA$ collisions, larger than is observed in central $AA$ collisions. The inhomogeneity may be measured by comparing the r…
Using a multi-phase transport (AMPT) model that includes the implementation of deformed Uranium nuclei, we have studied the centrality dependence of the charged particle multiplicity, <pT>, eccentricity (e2), triangularity (e3), their fluctuations, elliptic flow (v2) and triangular flow (v3) for different configurations of U+U collisions at midrapidity for \sqrt(s_NN)=200 GeV. The results are compared to the corresponding observations from Au+Au collisions. We find that for the U+U collisions the dNch/dηat midrapidity is enhanced by about 15-40% depending on the collision and model configurati…
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 photon-photon interaction in ultra-relativistic heavy-ion collision is a source of the $(e^+,e^-)$ pairs. The photon-photon fusion leads the lepton creation in the broad configuration space around "collision" point. Those created close to heavy nuclei may undergo strong interaction with them. The impact parameter space distribution of electrons and positrons are calculated within the b-space EPA model of such collisions. The evolution due to the electromagnetic interaction of $(e^+,e^-)$ with nuclei is studied, and the distortion of rapidity and transverse momentum distributions are shown.…
We calculate total and differential cross sections for $J/ψ$ photoproduction in ultrarelativistic lead-lead collisions at the LHC energy $\sqrt{s_{NN}}=2.76$ TeV. In the present approach we use a simple model based on vector dominance picture and multiple scattering of the hadronic ($c \bar c$) state in a cold nucleus as an example. In our analysis we use both the classical mechanics and quantum (Glauber) formulae for calculating $σ_{tot}(J/ψPb)$ which is a building block of our model. We compare our UPC results with ALICE and CMS data. For semi-central collisions ($b<R_A+R_B$) a modification …
Ultra-peripheral collisions (UPCs) of relativistic ions are an important tool for studying photoproduction at high energies. Vector meson photoproduction is an important tool for nuclear structure measurements and other applications. A future electron-ion collider (EIC) will allow additional studies, using virtual photons with a wide range of $Q^2$. We propose a significant expansion of the UPC and EIC photoproduction physics programs to include charged final states which may be produced via Reggeon exchange. We consider two examples: $a_2^+(1320)$, which is a conventional $q\overline q$ meson…
Effects of Geometric configuration in relativistic isobaric collisions at $\sqrt{s_{NN}}=200$ GeV
PDPM Indian Institute of Information Technology Design & Manufacturing（印度信息理工学院设计与制造学院）；Institute of Science, Banaras Hindu University (BHU)（贝拿勒斯印度教大学理学院）
Momentum correlation functions of light (anti)nuclei formed by the coalescence mechanism of (anti)nucleons are calculated for several central heavy-ion collision systems, namely $_{5}^{10}\textrm{B}+_{5}^{10}\textrm{B}$, $_{8}^{16}\textrm{O}+_{8}^{16}\textrm{O}$, $_{20}^{40}\textrm{Ca}+_{20}^{40}\textrm{Ca}$ as well as $_{79}^{197}\textrm{Au}+_{79}^{197}\textrm{Au}$ in different centralities at center of mass energy $\sqrt{s_{NN}}$ = 39 GeV within the framework of A Multi-Phase Transport (AMPT) model complemented by the Lednick$\acute{y}$ and Lyuboshitz analytical method. Momentum correlation …
We show that the data of $p_{T}$ spectra of $Ω^{-}$ and $ϕ$ at midrapidity in inelastic events in $pp$ collisions at $\sqrt{s}=$ 13 TeV exhibit a constituent quark number scaling property, which is a clear signal of quark combination mechanism at hadronization. We use a quark combination model under equal velocity combination approximation to systematically study the production of identified hadrons in $pp$ collisions at $\sqrt{s}$= 13 TeV. The midrapidity data of $p_{T}$ spectra of proton, $Λ$, $Ξ^{-}$, $Ω^{-}$, $ϕ$ and $K^{*}$ in inelastic events are simultaneously well fitted by the model. …
A simple power-law growth of charged-particle multiplicities near midrapidity in central Au+Au collisions at $\sqrt{s_{NN}}=56$ and 130 GeV, recently measured at RHIC, is derived. We give predictions for the central particle densities up to $\sqrt{s_{NN}}=1800$ GeV. A strong growth of the Au+Au densities above those for $\ol{p}(p)-p$ collisions is predicted.
We investigate the dependence of elliptic flows $v_2$ on transverse momentum $P_T$ for charged hadrons produced in nucleus-nucleus collisions at high energy by using a multi-source ideal gas model which includes the interaction contribution of the emission sources. Our calculated results are approximately in agreement with the experimental data over a wider $P_T$ range from the STAR and ALICE Collaborations. It is found that the expansion factor increases linearly with the impact parameter from most central (0-5%) to mid-peripheral (35-40%) collisions.
