Diffusion of heavy quarks in the early stage of high-energy nuclear collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider
J. H. Liu, S. Plumari, S. K. Das, V. Greco, M. Ruggieri
备注：
12 pages, 8+1 figures. Discussion on the scaling of parameters from three to two colors added in Appendix. Matches published version. arXiv admin note: text overlap with arXiv:1805.09617
We study the diffusion of charm and beauty in the early stage of high energy nuclear collisions at RHIC and LHC energies, considering the interaction of these heavy quarks with the evolving Glasma by means of the Wong equations. In comparison with previous works, we add the longitudinal expansion as well as we estimate the effect of energy loss due to gluon radiation. We find that heavy quarks diffuse in the strong transverse color fields in the very early stage (0.2-0.3 fm/c) and this leads to a suppression at low $p_T$ and enhancement at intermediate low $p_T$. The shape of the observed nuclear suppression factor obtained within our calculations is in qualitative agreement with the experimental results of the same quantity for $D-$mesons in proton-nucleus collisions. We compute the nuclear suppression factor in nucleus-nucleus collisions as well, for both charm and beauty, finding a substantial impact of the evolving Glasma phase on these, suggesting that initialization of heavy quarks spectra in the quark-gluon plasma phase should not neglect the early evolution in the strong gluon fields.
We use an event-by-event hydrodynamical description of the heavy-ion collision process with Glauber initial conditions to calculate the thermal emission of photons. The photon rates in the hadronic phase follow from a spectral function approach and a density expansion, while in the partonic phase they follow from the AMY perturbative rates. The calculated photon elliptic flows are lower than those reported recently by both the ALICE and PHENIX collaborations.
The complete understanding of the basic constituents of hadrons and the hadronic dynamics at high energies are two of the main challenges for the theory of strong interactions. In particular, the existence of intrinsic heavy quark components in the hadron wave function must be confirmed (or disproved). In this paper we propose a new mechanism for the production of $D$-mesons at forward rapidities based on the Color Glass Condensate (CGC) formalism and demonstrate that the resulting transverse momentum spectra are strongly dependent on the behavior of the charm distribution at large Bjorken $x$…
It is shown that the chemical freeze-out parameters obtained at CERN/SPS, BNL/AGS and GSI/SIS energies all correspond to a unique value of 1 GeV for the average energy per hadron.
We find that collective flow model which can successfully analyze charged particle distributions at AGS and lower SPS (less than 20Gev/n). but fails to analyze that of at RHIC. The tails of distribution of charged particle at RHIC has a jump from the collective flow model calculation as the energy increases. Thermalization Component Model is presented based on collective flow to study the multiplicity distributions at RHIC in this paper. It is realized that the region of phase space of collective flow can reflect that of thermalization region. By comparing the contributions of particle product…
We compute v4/(v2)^2 in ideal and viscous hydrodynamics. We investigate its sensitivity to details of the hydrodynamic model and compare the results to experimental data from RHIC. Whereas v2 has a significant sensitivity only to initial eccentricity and viscosity while being insensitive to freeze out temperature, we find that v4/(v2)^2 is quite insensitive to initial eccentricity. On the other hand, it can still be sensitive to shear viscosity in addition to freeze out temperature, although viscous effects do not universally increase v4/(v2)^2 as originally predicted. Consistent with data, we…
Hadronic resonances, having very short lifetime, like $\rm{K}^{*0}$, can act as useful probes to understand and estimate lifetime of hadronic phase in ultra-relativistic proton-proton, p--Pb and heavy-ion collisions. Resonances with relatively longer lifetime, like $ϕ$ meson, can serve as a tool to locate the QGP phase boundary. We estimate a lower limit of hadronic phase lifetime in Cu--Cu and Au--Au collisions at RHIC, and in pp, p--Pb and Pb--Pb collisions at different LHC collision energies. Also, we obtain the effective temperature of $ϕ$ meson using Boltzmann-Gibbs Blast-Wave function, w…
We present a modified colour screening model for $J/ψ$ suppression in the Quark-Gluon Plasma (QGP) using quasi-particle model (QPM) as equation of state (EOS). Other theoretical ingredients incorporated in the model are feed-down from higher resonances namely, $χ_c$, and $ψ^{'}$, dilated formation time for quarkonia and viscous effects of the QGP medium. Assuming further that the QGP is expanding with Bjorken's hydrodynamical expansion, the present model is used to analyze the centrality dependence of the $J/ψ$ suppression in mid-rapidity region and compare it with the data obtained from SPS, …
Widths of the rapidity distributions of various identified hadrons generated with the UrQMD-3.4 event generator at all the Super Proton Synchrotron (SPS) energies have been presented and compared with the existing experimental results. An increase in the width of the rapidity distribution of $Λ$ could be seen with both Monte Carlo (MC) and experimental data for the studied energies. Using MC data, the study has been extended to Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. A similar jump, as observed in the plot of rapidity width versus rest mass at Alternati…
Following the Boz$\dot{\textrm{e}}$k-Wyskiel parametrization tilted initial condition, an alternative way to construct a longitudinal tilted fireball based on the Glauber collision geometry is presented. This longitudinal tilted initial condition combined with the Ideal-CLVisc (3 + 1)D hydrodynamic model, a nonvanishing directed flow coefficient $v_{1}$ in a wide rapidity range is observed. After comparing the model's results with experimentally observed data of directed flow coefficient $v_{1}(η)$ from $\sqrt{s_{NN}}$ = 200 GeV Cu + Cu, Au + Au collisions at RHIC energy to $\sqrt{s_{NN}}$ = 2…
The charged particles produced in nucleus-nucleus collisions are divided into two parts. One is from the hot and dense matter created in collisions. The other is from leading particles. The hot and dense matter is assumed to expand according to unified hydrodynamics and freezes out into charged particles from a space-like hypersurface with a fixed proper time of Tau_FO.The leading particles are conventionally taken as the particles which inherit the quantum numbers of colliding nucleons and carry off most of incident energy. The rapidity distributions of the charged particles from these two pa…
We propose the development and construction of a novel muon-ion collider (MuIC) at Brookhaven National Laboratory (BNL) in the USA as an upgrade to succeed the electron-ion collider (EIC) that is scheduled to commence in the early 2030s, by a joint effort of the nuclear and particle physics communities. The BNL facility could accommodate a muon storage beam with an energy up to about 1~TeV with existing magnet technology. When collided with a 275~GeV hadron beam, the MuIC center-of-mass energy of about 1~TeV will extend the kinematic coverage of deep inelastic scattering physics at the EIC (wi…
It was proposed that the electric fields may lead to chiral separation in QGP, which is called the chiral electric separation effect. The strong electromagnetic field and the QCD vacuum can both completely be produced in the off-central nuclear-nuclear collision. We used the Wood-Saxon nucleon distribution to calculate the electric field distributions of the off-central collisions. The chiral electro field spatial distribution at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) energy regions are systematically studied in this paper. Compared with magnetic field spatial d…
We investigate the form of the viscous correction to the equilibrium distribution function in the context of a Cooper-Frye freeze out prescription for viscous hydrodynamic simulations of relativistic heavy ion collisions. The standard quadratic ansatz used by all groups for the case of shear viscosity is found to be disfavored by experimental data for v4/(v2)^2 at the Relativistic Heavy Ion Collider, and is unlikely to be correct for the hadron resonance gas present at freeze out. Instead, data for v2(pt) along with v4/(v2)^2 favor a momentum dependence between linear and quadratic.
We analyze the transverse momentum distribution of $J/ψ$ mesons produced in Au + Au collisions at the top RHIC energy within a blast-wave model that accounts for a possible inhomogeneity of the charmonium distribution and/or flow fluctuations. The results imply that the transverse momentum spectra of$J/ψ$, $ϕ$ and $Ω$ hadrons measured at the RHIC can be described well if kinetic freeze-out takes place just after chemical freeze-out for these particles.
In very high energy collisions nuclei are practically transparent to each other but produce very hot, nearly baryon-free, matter in the so-called central rapidity region. The energy in the central rapidity region comes from the kinetic energy of the colliding nuclei. We calculate the energy and rapidity loss of the nuclei using the color glass condensate model. This model also predicts the excitation energy of the nuclear fragments. Using a space-time picture of the collision we calculate the baryon and energy densities of the receding baryonic fireballs. For central collisions of gold nuclei …
The recent net-proton fluctuation results of the STAR (Solenoidal Tracker At RHIC) experiment from beam energy scan (BES) program at the BNL Relativistic Heavy Ion Collider (RHIC) have drawn much attention to exploring the QCD critical point and the nature of deconfinement phase transition. There has been much speculation that the non-monotonic behavior of $κσ^{2}$ of the produced protons around $\sqrt{s_{\rm NN}}$ = 19.6 GeV in the STAR results may be due to the existence of QCD critical point. However, the experimentally measured proton distributions contain protons from heavy resonance deca…
Using event-by-event fluctuations, we study the diffusion parameters of net-charge, net-pion, net-kaon, and net-proton in the heavy-ion jet interaction generator (HIJING), and ultra-relativistic quantum molecular dynamics (UrQMD) models at different collision energies \sqsn available at BNL Relativistic Heavy Ion Collider (RHIC). The diffusion parameter ($σ$) of net-charge and identified particles are estimated in rapidity space at various \sqsn. It is observed that, the $σ$ values are independent of collision energies but emphasises the particle-species dependence of diffusion coefficient in …
Three-particle azimuthal correlation measurements with a high transverse momentum trigger particle are reported for pp, d+Au, and Au+Au collisions at 200 GeV by the STAR experiment. Dijet structures are observed in pp, d+Au and peripheral Au+Au collisions. An additional structure is observed in central Au+Au data, signaling conical emission of correlated charged hadrons. The conical emission angle is found to be 1.37 +- 0.02(stat) +0.06-0.07(syst), independent of pt.
Within the framework of intermittency analysis, a search for critical fluctuations is ongoing to locate the possible critical point in the quantum chromodynamics phase diagram. In this study, self-similar critical fluctuations from a critical Monte Carlo (CMC) model have been incorporated into the cascade ultrarelativistic quantum molecular dynamics (UrQMD) model. This hybrid UrQMD+CMC model exhibits a clear power-law behavior of scaled factorial moment for charged particles in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7-200 GeV. By comparing the UrQMD+CMC model results with those from th…
We study the nuclear modification of angular and momentum correlations between heavy quark pairs in ultrarelativistic heavy-ion collisions. The evolution of heavy quarks inside the thermalized medium is described via a modified Langevin approach that incorporates both elastic and inelastic interactions with the medium constituents. The spacetime evolution of the fireball is obtained from a (2+1)-dimensional viscous hydrodynamics simulation. The hadronization of heavy quarks is performed utilizing a hybrid model of fragmentation and coalescence. Our results show that the nuclear modification of…
We suggest that the "new form of matter" found just above $T_c$ by RHIC is made up of tightly bound quark-antiquark pairs, essentially 32 chirally restored (more precisely, nearly massless) mesons of the quantum numbers of $π$, $σ$, $ρ$ and $a_1$. Taking the results of lattice gauge simulations (LGS) for the color Coulomb potential from the work of the Bielefeld group and feeding this into a relativistic two-body code, after modifying the heavy-quark lattice results so as to include the velocity-velocity interaction, all ground-state eigenvalues of the 32 mesons go to zero at $T_c$ just as the…
Based on the recent RHIC and LHC experimental results, the $\langle p_T\rangle$ dependence of identified light flavour charged hadrons on $\sqrt{(\frac{dN}{dy})/S_{\perp}}$, relevant scale in gluon saturation picture, is studied from $\sqrt{s_{NN}}$=7.7 GeV up to 5.02 TeV. This study is extended to the slopes of the $\langle p_T\rangle$ dependence on the particle mass and the $\langleβ_T\rangle$ parameter from Boltzmann-Gibbs Blast Wave (BGBW) fits of the $p_T$ spectra. A systematic decrease of the slope of the $\langle p_T\rangle$ dependence on $\sqrt{(\frac{dN}{dy})/S_{\perp}}$ from BES to t…
Local density fluctuations near the QCD critical point has been suggested to exhibit a power-law behavior which can be probed by an intermittency analysis on scaled factorial moment (SFM) in relativistic heavy-ion collisions. The collision energy and centrality dependence of the second-order SFMs are systematically investigated in Au $+$ Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV within the UrQMD model. We estimate the noncritical background in the measurement of intermittency and propose a cumulative variable method to effectively remove the background contr…
We study the fluctuations of net-charge, net-pion, net-kaon and net-proton using $D$-measure and $ν_{dyn}$ variables in heavy-ion jet interaction generator (HIJING), ultra-relativistic quantum molecular dynamics (UrQMD), and hadron resonance gas (HRG) model at different collision energies \sqsn. It has been observed that, the values of $D$ strongly dependent on $Δη$ in HIJING and UrQMD models and independent in HRG model. The diffusion coefficients ($σ$) of identified particles are estimated at various \sqsn. It is observed that, the $σ$ values are independent of collision energies but emphasi…
The revised Landau hydrodynamic model is used to discuss the pseudorapidity distributions of the produced charged particles in Au+Au and Cu+Cu collisions at energies of sqrt(s_NN)= 19.6 and 22.4 GeV correspondingly on the BNL Relativistic Heavy Ion Collider. It is found that the revised Landau hydrodynamic model alone can give a good description to the experimental measurements. This is different from that in the same collisions but at the maximum energy of sqrt(s_NN)= 200 GeV. Where, in addition to the revised Landau hydrodynamic model, the effects of leading particles have to be taken into a…
Different orientations of $α$-clustered carbon nuclei colliding with heavy ions can result in a large variation in the value of anisotropic flow. Thus, photon flow observables from clustered ${\rm^{12}C}$ and ${\rm^{197}Au}$ collisions could be a potential probe to study the `direct photon puzzle'. We calculate the transverse momentum spectra and anisotropic flow coefficients ($v_n$) of thermal photons from collisions of triangular $α$-clustered carbon and gold at $\sqrt{s_{\rm NN}}=200$ GeV at RHIC using a hydrodynamic model framework and compare the results with those obtained from uncluster…
We argue that measurements of identified-particle elliptic flow in a wide energy range could shed light on the possible phase change in high-energy heavy ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC). When the hadronization process is dominated by quark coalescence, the number-of-constituent-quark (NCQ) scaling for the identified-particle elliptic flow can serve as a probe for studying the strong interacting partonic matter. In the upcoming RHIC low-energy runs, the NCQ scaling behavior may be broken because of the change of the effective degrees of freedom of the hot dense …
We investigate the energy losses of $b$ and $c$ quarks at hard collisions with gluons and light quarks in quark-gluon plasma produced in central $Au + Au$ collisions at RHIC energy($\sqrt{s_{NN}} = 200$ GeV). As the coupling constant at hard collision in the perturbative QCD is limited by Landau pole at momenta $Q^{2} = Λ^{2}$, we use the analytic models of QCD, where the Landau pole is absent. We calculate the energy losses of $b$ and $c$ quarks in analytic model of QCD at $Q^{2} \ge Λ^{2}$. At calculations we use the effective quasiparticle model. We use at calculations of total nuclear modi…
The meson production cross sections are estimated considering photon-photon interactions in hadron - hadron collisions at CERN LHC energies. We consider a large number of mesons with photon-photon partial decay width well constrained by the experiment and some mesons which are currently considered as hadronic molecule and glueball candidates. Our results demonstrate that the experimental analysis of these states is feasible at CERN - LHC.
We study in details the space-time dependence of the production of muonic, pionic, and other exotic atoms by the coherent photon exchange between nuclei at the Large Hadron Collider at CERN. We show that a multipole expansion of the electromagnetic interaction yields an useful insight of the bound-free production mechanism which has not been explored in the literature. Predictions for the spatial, temporal, and angular distribution, as well as the total cross sections, for the production of exotic atoms are also included.
Proton-proton (pp) collisions have been traditionally used as a baseline measurement in the search for a deconfined state of matter in heavy-ion collisions at ultrarelativistic energies. The unprecedented collision energies that are available at the Large Hadron Collider (LHC) at the European Laboratory for Nuclear Research (CERN) have illuminated new challenges in understanding the possible formation of droplets of this deconfined matter of partonic degrees of freedom in hadronic collisions, especially in high-multiplicity events. Enhancement of multi-strange particles compared to pions, degr…
We investigate with a transport approach the cold and hot nuclear matter effects on the charmonium transverse momentum distributions in relativistic heavy ion collisions. The newly defined nuclear modification factor $r_{AA}=\langle p_{T}^2\rangle_{AA}/\langle p_{T}^2\rangle_{pp}$ and elliptic flow $v_2$ for $J/ψ$ are sensitive to the nature of the hot medium and the thermalization of heavy quarks. From SPS through RHIC to LHC colliding energies, we observe dramatic changes in the centrality dependence of $r_{AA}$. We find that at LHC energy, the finally observed charmonia are dominated by the…
We review current results on physics with photons at the LHC and discuss realistic perspectives of photon physics at future colliders. In particular, we focus on Standard Model (SM) measurements with photons at the upcoming high-luminosity and a possible high-energy LHC as well as jet measurements at an Electron-Ion Collider (EIC) to be constructed either at BNL or at JLAB and their potential to constrain nuclear parton densities. We also discuss future searches for physics beyond the SM with photons in the high-luminosity phase of the LHC.
We study the momentum dependence of the production of light nuclei in high energy collisions in the nucleon coalescence/recombination mechanism. We derive formulas of the momentum distributions of deuterons ($d$) and helions ($^3$He). We obtain the analytic expressions of the coalescence factor $B_A$'s ($B_2$ for $d$ and $B_3$ for $^3$He) as functions of the collision system size and the momentum. We apply the deduced results to p-p, p-Pb and Pb-Pb collisions to naturally explain the interesting behaviors of $B_A$ observed in experiments at the CERN Large Hadron Collider.
The features of net baryon productions and collective flow in relativistic heavy-ion collisions at energies reached at the CERN Large Hadron Collider (LHC), BNL Relativistic Heavy Ion Collider (RHIC), CERN Super Proton Synchrotron (SPS) and BNL Alternating Gradient Synchrotron (AGS) with the model of Non-Uniform Flow Model(NUFM) are systematically studied in this paper. Especially we predict the feature of net baryon productions and collective flow at LHC $\sqrt{s_{NN}}$=5500 GeV basing on the detailed study of that at RHIC $\sqrt{s_{NN}}$=62.4 and 200GeV. The dependencies of the features of b…
Photoproduction of heavy quarks in ultraperipheral collisions can help elucidate important features of the physics of heavy quarks in Quantum Chromodynamics (QCD). Due to the dependence on parton distributions it can also potentially offer some constraining ability in the determination of nuclear parton distributions. In the present study we consider next-to-leading order (NLO) photoproduction of heavy quarks in ultraperipheral proton-proton (pp), proton-nucleus (pA), and nucleus-nucleus (AA) collisions at the CERN Large Hadron Collider (LHC). Total cross sections and rapidity distributions ar…
We study in details the space-time dependence of the production of muonic, pionic, and other exotic atoms by the coherent photon exchange between nuclei at the Large Hadron Collider (LHC) at CERN. We show that a multipole expansion of the electromagnetic interaction yields an useful insight of the bound-free production mechanism which has not been explored in the literature. Predictions for the spatial, temporal, and angular distribution, as well as the total cross sections, for the production of exotic atoms are also included.
With the HIJING/BBbar v2.0 heavy ion event generator, we explore the phenomenological consequences of several high parton density dynamical effects predicted in central Pb+Pb collisions at the Large Hadron Collider (LHC) energies. These include (1) jet quenching due to parton energy loss (dE/dx), (2) strangeness and hyperon enhancement due to strong longitudinal color field (SCF), and (3) enhancement of baryon-to-meson ratios due to baryon-anti-baryon junctions (JJbar) loops and SCF effects. The saturation/minijet cutoff scale p0(s)and effective string tension kappa(s,A) are constrained by our…
The hydrokinetic approach, that incorporates hydrodynamic expansion of the systems formed in A+A collisions and their dynamical decoupling, is applied to restore the initial conditions and space-time picture of the matter evolution in central Au+Au collisions at the top RHIC energy. The analysis is based on the detailed reproduction of the pion and kaon momentum spectra and femtoscopic data in whole interval of the transverse momenta studied by both STAR and PHENIX collaborations. The fitting procedure utilizes the two parameters: the maximal energy density at supposed thermalization time 1 fm…
Highlights of the results from ultrarelativistic heavy ion collisions at CERN-SPS are reviewed. In particular, I discuss how the experimental results indicate that a collective strongly interacting system has been produced, and what are the implications towards the Quark Gluon Plasma. The physical ideas behind measuring certain observables are introduced. The future program of high energy nuclear collisions at BNL-RHIC and CERN-LHC/ALICE is also briefly discussed.
A simultaneous blast-wave fit to particle yields and elliptic flow ($v_{2}$) measured as a function of transverse momentum in Pb-Pb collisions at LHC energies is presented. A compact formula for the calculation of $v_2(p_T)$ for an elliptic freeze-out surface is used which follows from the Cooper-Frye ansatz without further assumptions. Over the full available $p_T$ range, the $Υ$ elliptic flow data is described by the prediction based on the fit to lighter particles. This prediction shows that, due to the large $Υ$ mass, a sizable elliptic flow is only expected at transverse momenta above 10 …
I compare the first viscous hydrodynamic prediction for integrated elliptic flow in Pb-Pb collisions at the LHC with the first data released by the ALICE collaboration. These new data are found to be consistent with hydrodynamic extrapolations of RHIC data with no change in medium parameters (e.g., average viscosity). I also discuss how, in general, a precise comparison of data to theoretical calculations requires an understanding of some subtleties of the measurement -- most notably the cut on transverse momentum of the particles used and the differing sensitivities to flow fluctuations and n…
We study the production and equilibration of the gluon-minijet plasma expected to be formed in the central region of ultrarelativistic heavy-ion collisions at the BNL-RHIC and the CERN-LHC by solving a self-consistent relativistic transport equation. We compute the minijet production within perturbative QCD. Subsequent collisions among the semi-hard partons are treated by considering the elastic gg -> gg processes with screening of the long wavelength modes taken into account. We determine the time $τ_{eq}$ where close to ideal hydrodynamic flow sets in, and find rather similar numbers for cen…
Tagged jet measurements provide a promising experimental channel to quantify the similarities and differences in the mechanisms of jet production in proton-proton and nucleus-nucleus collisions. We present the first calculation of the transverse momentum asymmetry of Z^0/gamma^*-tagged jet events in sqrt{s}=2.76$ TeV reactions at the LHC. Our results combine the O(G_Fα_s^2) perturbative cross sections with the radiative and collisional processes that modify parton showers in the presence of dense QCD matter. We find that a strong asymmetry is generated in central lead-lead reactions that has l…
Cross sections are calculated for single and double photon exchange in ultraperipheral Pb+Pb collisions at the LHC. The particle production is simulated with the DPMJET event generator. Large cross sections are found for particle production around mid-rapidity making these processes an important background to hadronic nuclear interactions at both the trigger and analysis levels.
This is a short survey of signatures and characteristics of the quark-gluon plasma in the light of experimental results that have been obtained over the past three decades. In particular, we present an in-depth discussion of the strangeness observable, including a chronology of the experimental effort to detect QGP at CERN-SPS, BNL-RHIC, and CERN-LHC.
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…
Vector meson production in ultra-peripheral pA and AA collisions at the CERN Large Hadron Collider (LHC) are very sensitive to Parton Distribution Functions (PDF) as well as to their leading-order, next-to-leading-order, and medium corrections. This process is a complimentary tool to explore the effects of different PDFs in particle production in proton-nucleus and nucleus-nucleus central collisions. Existing and forthcoming data available, e.g., from ALICE and CMS, may be used in conjunction with our theoretical predictions to constrain the PDFs. We make predictions for rapidity distributions…
We make predictions for the cross sections of coherent photoproduction of $ρ$, $ϕ$, $J/ψ$, $ψ(2S)$, and $Υ(1S)$ mesons in Pb-Pb ultraperipheral collisions (UPCs) at $\sqrt{s_{NN}}=5.02$ TeV in the kinematics of run 2 at the Large Hadron Collider extending the approaches successfully describing the available Pb-Pb UPC data at $\sqrt{s_{NN}}=2.76$ TeV. Our results illustrate the important roles of hadronic fluctuations of the photon and inelastic nuclear shadowing in photoproduction of light vector mesons on nuclei and the large leading twist nuclear gluon shadowing in photoproduction of quarkon…
We use experimentally measured identified particle spectra and Hanbury Brown-Twiss radii to determine the entropy per unit rapidity $dS/dy$ produced in $\sqrt{s} = 7$ TeV pp and $\sqrt{s_{\rm NN}} = 2.76$ TeV Pb-Pb collisions. We find that $dS/dy = 11335 \pm 1188$ in 0-10% Pb-Pb, $dS/dy = 135.7 \pm 17.9$ in high-multiplicity pp, and $dS/dy = 37.8 \pm 3.7$ in minimum bias pp collisions and compare the corresponding entropy per charged particle $(dS/dy)/(dN_{\rm ch}/dy)$ to predictions of statistical models. Finally, we use the QCD kinetic theory pre-equilibrium and viscous hydrodynamics to mode…
We present calculations for the incoherent photoproduction of J/$ψ$ vector mesons in ultra-peripheral heavy ion collisions (UPC) in terms of hadronic interactions. This study was carried out using the recently developed Monte Carlo model CRISP extended to include UPCs at LHC energies. A careful study of re-scattering and destruction of the J/$ψ$ particles is presented for PbPb collisions at $\sqrt{s_{NN}} = 2.76$ TeV. We have also compared our method to AuAu collisions at $\sqrt{s_{NN}} = 200$ GeV measured at RHIC.
Meson production cross sections in ultra-peripheral relativistic heavy ion collisions at LHC are revisited. The relevance of meson models and of exotic QCD states is discussed. This study includes states that have not been considered before in the literature.
Using updated gluon distributions from global fits to data, we investigate the sensitivity of direct photoproduction of heavy quarks and exclusive production of vector mesons to varying strength of gluon modifications. Implications of using these processes for constraining nuclear gluon distributions are discussed.
At Large Hadron Collider energy, the expected large multiplicities suggests the presence of collective behavior even in pp collisions. A hydrodynamical approach has been applied to estimate the expected elliptic flow measured by the azimuthal asymmetry parameter $v_2$, in pp collisions at $\surd$s = 14 TeV. $v_2$ of $π^-$ is found to be strongly dependent on the parton density profile inside a proton [e.g., surface diffuseness parameter ($ξ$)]. For $ξ$ = 0.105, $v_2$ is found to be positive while at $ξ$ = 0.25, $v_2$ is close to zero and approaches negative values at large $p_t$. The impact pa…
We compute cross sections for incoherent and coherent diffractive J/Psi production in ultraperipheral nucleus-nucleus and proton-nucleus collisions using two different dipole models fitted to HERA data. We obtain a reasonably good description of the available ALICE data for coherent J/Ψproduction and present our prediction for the incoherent cross section. We also find that while the normalization of the cross section depends quite strongly on the dipole model and vector meson wave function used, the rapidity dependence is very well constrained.
