Nuclear Theory·nucl-th

Monday·September 19, 2016

10 papers—5 primary·5 cross-listed

06
Psi(2S) Production at the LHC
Xiaojian Du🇺🇸 · Ralf Rapp🇺🇸
We calculate the production of $ψ (2 S)$ and the pertinent double ratio of its nuclear modification factor ( $R_{AA}$ ) over that of the $J / ψ$ in Pb-Pb collisions at the LHC. Based on a transport model with temperature dependent reaction rates, a sequential regeneration pattern emerges: the larger $ψ (2 S)$ width, relative to the $J / ψ$ , around and below the critical temperature, implies that most of the $ψ (2 S)$ states are regenerated later in the evolution of the fireball. This has noticeable consequences for the transverse-momentum ( $p_{T}$ ) spectra of the regenerated charmonia. While the total yield of $ψ (2 S)$ meson remains smaller than those of $J / ψ$ 's, their harder $p_{T}$ spectra can produce a double ratio above unity for a $p_{T} > 3$ GeV cut, as applied by the CMS collaboration. A significant uncertainty in our calculations is associated with the values of the temperature where most of the $ψ (2 S)$ regeneration occurs, the quantitative temperature dependence of its inelastic width.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2017)·10 citations
07
$T$ -Matrix Approach to Strongly Coupled QGP
Shuai Y.F. Liu🇺🇸 · Ralf Rapp🇺🇸
Based on a thermodynamic $T$ -matrix approach we extract the potential $V$ between two static charges in the quark-gluon plasma (QGP) from fits to the pertinent lattice-QCD free energy. With suitable relativistic corrections we utilize this new potential to compute heavy-quark transport coefficients and compare the results to previous calculations using either $F$ or $U$ as potential. We then discuss a generalization of the $T$ -matrix re-summation to a "matrix $lo g$ " re-summation of $t$ -channel diagrams for the grand partition function of the QGP in the Luttinger-Ward skeleton diagram formalism. With $V$ as a non-perturbative driving kernel in the light-parton sector, we obtain the QGP equation of state from fits to lattice-QCD data. The resulting light-parton spectral functions are characterized by large thermal widths at small momenta, indicating the dissolution of quasi-particles in a strongly coupled QGP.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2017)·6 citations
08
Theory overview of Heavy Ion collisions
T. Lappi🇫🇮
This presentation discusses some recently active topics in the theoretical interpretation of high energy heavy ion collisions at the LHC and at RHIC. We argue that the standard paradigm for understanding the spacetime evolution of the bulk of the matter produced in the collision is provided by viscous relativistic hydrodynamics, which can be used to systematically extract properties of the QCD medium from experimental results. The initial conditions of this hydrodynamical evolution are increasingly well understood in terms of gluon saturation, and can be quantified using Classical Yang-Mills fields and QCD effective kinetic theory. Hard and electromagnetic probes of the plasma provide additional constraints. A particularly fascinating subject are high multiplicity proton-proton and proton-nucleus collisions, where some of the characteristics previously attributed to only nucleus-nucleus collisions have been observed.
↳ hep-phnucl-thPoS(2016)·3 citations
09
Photoproduction of a large invariant mass $γ ρ$ pair at small momentum transfer
R. Boussarie🇫🇷 · B. Pire🇫🇷 · L. Szymanowski🇵🇱 · S. Wallon🇫🇷
The collinear factorization framework allows to describe the exclusive photoproduction of a $γ ρ$ pair in the generalized Bjorken regime in terms of a perturbatively calculable coefficient function and universal generalized parton distributions. The kinematics are defined by a large invariant mass of the $γ ρ$ pair and a small transverse momentum of the final nucleon. We calculate the scattering amplitude at leading order in $α_{s}$ and the differential cross sections for the process where the $ρ -$ meson is either longitudinally or transversely polarized, in the kinematics of the near future Jlab experiments. Our estimate of the cross section demonstrates that this process is measurable at JLab 12-GeV.
↳ hep-phhep-exnucl-exnucl-thPoS(2016)·0 citations
10
Neutrino emissivities and bulk viscosity in neutral two-flavor quark matter
J. Berdermann🇩🇪 · D. Blaschke🇵🇱 · T. Fischer🇵🇱 · A. Kachanovich🇵🇱
We study thermodynamic and transport properties for the isotropic color-spin-locking (iso-CSL) phase of two-flavor superconducting quark matter under compact star constraints within a NJL-type chiral quark model. Chiral symmetry breaking and the phase transition to superconducting quark matter leads to a density dependent change of quark masses, chemical potentials and diquark gap. A self-consistent treatment of these physical quantities influences on the microscopic calculations of transport properties. We present results for the iso-CSL direct URCA emissivities and bulk viscosities, which fulfill the constraints on quark matter derived from cooling and rotational evolution of compact stars. We compare our results with the phenomenologically successful, but yet heuristic 2SC+X phase. We show that the microscopically founded iso-CSL phase can replace the purely phenomenological 2SC+X phase in modern simulations of the cooling evolution for compact stars with color superconducting quark matter interior.
↳ astro-ph.HEnucl-thPRD(2016)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE

Psi(2S) Production at the LHC

T-Matrix Approach to Strongly Coupled QGP

Theory overview of Heavy Ion collisions

Photoproduction of a large invariant mass γρ pair at small momentum transfer

Neutrino emissivities and bulk viscosity in neutral two-flavor quark matter

Affiliations

$T$ -Matrix Approach to Strongly Coupled QGP

Photoproduction of a large invariant mass $γ ρ$ pair at small momentum transfer