53135280
Azimuthal jet flavor tomography with CUJET2.0 of nuclear collisions at RHIC and LHC
A bstractA perturbative QCD based jet tomographic Monte Carlo model, CUJET2.0, is presented to predict jet quenching observables in relativistic heavy ion collisions at RHIC/BNL and LHC/CERN energies. This model generalizes the DGLV theory of flavor dependent radiative energy loss by including multi-scale running strong coupling effects. It generalizes CUJET1.0 by computing jet path integrations though more realistic 2 + 1D transverse and longitudinally expanding viscous hydrodynamical fields contrained by fits to low pT flow data. The CUJET2.0 output depends on three control parameters, (αmax, fE, fM ), corresponding to an assumed upper bound on the vacuum running coupling in the infrared and two chromo-electric and magnetic QGP screening mass scales (fEμ(T ), fMμ(T )) where μ(T ) is the 1-loop Debye mass. We compare numerical results as a function of αmax for pure and deformed HTL dynamically enhanced scattering cases corresponding to (fE = 1, 2, fM = 0) to data of the nuclear modification factor, RAAf(pT, ϕ; s,b$$ \sqrt{s}, b $$) for jet fragment flavors f = π, D, B, e at s$$ \sqrt{s} $$ = 0.2 − 2.76 ATeV c.m. energies per nucleon pair and with impact parameter b = 2.4, 7.5 fm. A χ2 analysis is presented and shows that RAAπ data from RHIC and LHC are consistent with CUJET2.0 at the χ2/d.o.f < 2 level for αmax = 0.23 − 0.30. The corresponding q^$$ \widehat{q} $$(Ejet, T )/T3 effective jet transport coefficient field of this model is computed to facilitate comparison to other jet tomographic models in the literature. The predicted elliptic asymmetry, v2(pT ; s$$ \sqrt{s} $$, b) is, however, found to significantly underestimated relative to RHIC and LHC data. We find the χv22$$ {\chi}_{v_2}^2 $$ analysis shows that v2 is very sensitive to allowing even as little as 10% variations of the path averaged αmax along in and out of reaction plane paths.
124654178
Extracting the jet transport coefficient from jet quenching in high-energy heavy-ion collisions
Within five different approaches to parton propagation and energy loss in dense matter, a phenomenological study of experimental data on suppression of large $p_T$ single inclusive hadrons in heavy-ion collisions at both RHIC and LHC was carried out. The evolution of bulk medium used in the study for parton propagation was given by 2+1D or 3+1D hydrodynamic models which are also constrained by experimental data on bulk hadron spectra. Values for the jet transport parameter $\hat q$ at the center of the most central heavy-ion collisions are extracted or calculated within each model, with parameters for the medium properties that are constrained by experimental data on the hadron suppression factor $R_{AA}$. For a quark with initial energy of 10 GeV we find that $\hat q\approx 1.2 \pm 0.3$ GeV$^2$/fm at an initial time $\tau_0=0.6$ fm/$c$ in Au+Au collisions at $\sqrt{s}=200$ GeV/n and $\hat q\approx 1.9 \pm 0.7 $ GeV$^2$/fm in Pb+Pb collisions at $\sqrt{s}=2.76 $ TeV/n. Compared to earlier studies, these represent significant convergence on values of the extracted jet transport parameter, reflecting recent advances in theory and the availability of new experiment data from the LHC.
59393216
J/psi production and elliptic flow in relativistic heavy-ion collisions
Using the two-component model for charmonium production, which includes contributions from both initial hard nucleon-nucleon scattering and from regeneration in the quark-gluon plasma, we study the nuclear modification factor R{sub AA} and elliptic flow v{sub 2} of J/{psi} in relativistic heavy-ion collisions. For the expansion dynamics of produced hot, dense matter, we introduce a schematic fireball model with its transverse acceleration determined from the pressure gradient inside the fireball and azimuthally anisotropic expansion parametrized to reproduce measured v{sub 2} of light hadrons. We assume that light hadrons freeze out at the temperature of 120 MeV while charmonia freeze out at 160 MeV, similar to the kinetic and chemical freeze-out temperatures in the statistical model, respectively. For the properties of charmonia in the quark-gluon plasma, we use the screening mass between their charm and anticharm quarks and their dissociation cross sections given by the perturbative quantum chromodynamical (pQCD) calculations in the leading order and up to the next-to-leading order, respectively. For the relaxation time of charm and anticharm quarks in the quark-gluon plasma, we also use the one calculated in the leading-order pQCD. Modeling the effect of higher-order corrections in pQCD by introducing multiplicative factors to the dissociation cross sections ofmore » charmonia and the elastic scattering cross sections of charm and anticharm quarks, we find that this effect is small for the R{sub AA} of J/{psi} as they suppress the number of initially produced J/{psi} but enhance the number of regenerated ones. The higher-order corrections increase, however, the v{sub 2} of J/{psi}. Our results suggest that the v{sub 2} of J/{psi} can play an important role in discriminating between J/{psi} production from initial hard collisions and from regeneration in the quark-gluon plasma.« less
119110703
12CO J=2?1 and 12CO J=3?2 observations toward the high-mass protostellar candidate IRAS 20188+3928
We have carried out observations of 12 CO J =2–1 and 12 CO J =3–2 toward the high-mass protostellar candidate IRAS 20188+3928. Compared with previous observations, the 12 CO J =2–1 and 12 CO J =3–2 lines both have asymmetric profiles with an absorption dip. The velocity of the absorption dip is ~ 1.0 km s −1 . The spectral shape may be caused by rotation. The velocity-integrated intensity map and position-velocity diagram of the 12 CO J =2–1 line present an obvious bipolar component, further verifying that this region has an outflow motion. This region is also associated with an HII region, an IRAS source, and an H 2 O maser. The H 2 O maser has the velocity of 1.1 km s −1 . Compared with the components of the outflow, we find that the H 2 O maser is not associated with the outflow. Using the large velocity gradient model, we concluded that possible averaged gas densities of the blueshifted lobe and redshifted lobe are 1.0×10 5 cm −3 and 2.0×10 4 cm −3 , while kinetic temperatures are 26.9 K and 52.9 K, respectively. Additionally, the outflow has a higher integrated intensity ratio ( I CO J =3−2 / I CO J =2−1 ).
119210814
Higher-order anisotropic flows and dihadron correlations in Pb-Pb collisions at sNN=2.76 TeV in a multiphase transport model
Using a multiphase transport model that includes both initial partonic and final hadronic scatterings, we have studied higher-order anisotropic flows as well as dihadron correlations as functions of pseudorapidity and azimuthal angular differences between trigger and associated particles in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. With parameters in the model determined previously from fitting the measured multiplicity density of mid-pseudorapidity charged particles in central collisions and their elliptic flow in mid-central collisions, the calculated higher-order anisotropic flows from the two-particle cumulant method reproduce approximately those measured by the ALICE Collaboration, except at small centralities where they are slightly overestimated. Similar to experimental results, the two-dimensional dihadron correlations at most central collisions show a ridge structure at the near side and a broad structure at the away side. The short- and long-range dihadron azimuthal correlations, corresponding to small and large pseudorapidity differences, respectively, are studied for triggering particles with different transverse momenta and are found to be qualitatively consistent with experimental results from the CMS Collaboration. The relation between the short-range and long-range dihadron correlations with that induced by back-to-back jet pairs produced from initial hard collisions is also discussed.
119095770
Temperature effects on the nuclear symmetry energy and symmetry free energy with an isospin and momentum dependent interaction
Within a self-consistent thermal model using an isospin and momentum dependent interaction (MDI) constrained by the isospin diffusion data in heavy-ion collisions, we investigate the temperature dependence of the symmetry energy ${E}_{\mathrm{sym}}(\ensuremath{\rho},T)$ and symmetry free energy ${F}_{\mathrm{sym}}(\ensuremath{\rho},T)$ for hot, isospin asymmetric nuclear matter. It is shown that the symmetry energy ${E}_{\mathrm{sym}}(\ensuremath{\rho},T)$ generally decreases with increasing temperature while the symmetry free energy ${F}_{\mathrm{sym}}(\ensuremath{\rho},T)$ exhibits opposite temperature dependence. The decrement of the symmetry energy with temperature is essentially due to the decrement of the potential energy part of the symmetry energy with temperature. The difference between the symmetry energy and symmetry free energy is found to be quite small around the saturation density of nuclear matter. While at very low densities, they differ significantly from each other. In comparison with the experimental data of temperature dependent symmetry energy extracted from the isotopic scaling analysis of intermediate mass fragments (IMF's) in heavy-ion collisions, the resulting density and temperature dependent symmetry energy ${E}_{\mathrm{sym}}(\ensuremath{\rho},T)$ is then used to estimate the average freeze-out density of the IMF's.
118606308
Pure Neutron Matter Constraints and Nuclear Symmetry Energy
In this review, we will discuss the results of our recent work [1] to study the general optimization of the pure isovector parameters of the popular relativistic mean-field (RMF) and Skyrme-Hartree-Fock (SHF) nuclear energy-density functionals (EDFs), using constraints on the pure neutron matter (PNM) equation of state (EoS) from recent ab initio calculations. By using RMF and SHF parameterizations that give equivalent predictions for ground-state properties of doubly magic nuclei and properties of symmetric nuclear matter (SNM) and PNM, we found that such optimization leads to broadly consistent symmetry energy J and its slope parameter L at saturation density within a tight range of α(J) < 2 MeV and α(L) < 6 MeV. We demonstrate that a clear model dependence shows up (a) in the curvature parameter of the symmetry energy Ksym, (b) the symmetry energy at supra-saturation densities, and (c) the radius of neutron stars.