Altas Energias

Danuce M. Dudek, Wei-Liang Qian, Chen Wu, Otávio Socolowski, Sandra S. Padula, Gastão Krein, Yogiro Hama and Takeshi Kodama

International Journal of Modern Physics E (no momento online apenas,
publicado em 2018/6/24)

ABSTRACT

We perform an extensive study of the role played by the equation of state (EoS) in the hydrodynamic evolution of the matter produced in relativistic heavy ion collisions. By using the same initial conditions and freeze-out scenario, the effects of different equations of state are compared by calculating their respective hydrodynamical evolution, particle spectra, harmonic flow coefficients v2v2, v3v3 and v4v4 and two-pion interferometry radius parameters. The equations of state investigated contain distinct features, such as the nature of the phase transition, as well as strangeness and baryon density contents, which are expected to lead to different hydrodynamic responses. The results of our calculations are compared to the data recorded at two RHIC energies, 130GeV and 200GeV. The three equations of state used in the calculations are found to describe the data reasonably well. Differences can be observed among the studied observables, but they are quite small. In particular, the collective flow parameters are found not to be sensitive to the choice of the EOS, whose implications are discussed.

DOI:10.1142/S0218301318500581

M. GREIF; J. A. FOTAKIS; G. S. Denicol; C. GREINER

PHYSICAL REVIEW LETTERS, v. 120, p. 242301, 2018

Abstract

We demonstrate that the diffusion currents do not depend only on gradients of their corresponding charge density, but that the different diffusion charge currents are coupled. This happens in such a way that it is possible for density gradients of a given charge to generate dissipative currents of another charge. Within this scheme, the charge diffusion coefficient is best viewed as a matrix, in which the diagonal terms correspond to the usual charge diffusion coefficients, while the off-diagonal terms describe the coupling between the different currents. In this Letter, we calculate for the first time the complete diffusion matrix for hot and dense nuclear matter, including baryon, electric, and strangeness charges. We find that the baryon diffusion current is strongly affected by baryon charge gradients but also by its coupling to gradients in strangeness. The electric charge diffusion current is found to be strongly affected by electric and strangeness gradients, whereas strangeness currents depend mostly on strange and baryon gradients.

10.1103/PhysRevLett.120.242301

M.Broilo, E.G.S.Luna and M.J.Menon

Physics Letters B. Volume 781, p. 616-620. 10 June 2018.

ABSTRACT

Recent data from LHC13 by the TOTEM Collaboration on and ρ have indicated disagreement with all the Pomeron model predictions by the COMPETE Collaboration (2002). On the other hand, as recently demonstrated by Martynov and Nicolescu (MN), the new datum and the unexpected decrease in the ρ value are well described by the maximal Odderon dominance at the highest energies. Here, we discuss the applicability of Pomeron dominance through fits to the most complete set of forward data from pp and scattering. We consider an analytic parameterization for consisting of non-degenerated Regge trajectories for even and odd amplitudes (as in the MN analysis) and two Pomeron components associated with double and triple poles in the complex angular momentum plane. The ρ parameter is analytically determined by means of dispersion relations. We carry out fits to pp and data on and ρ in the interval 5 GeV–13 TeV (as in the MN analysis). Two novel aspects of our analysis are: (1) the dataset comprises all the accelerator data below 7 TeV and we consider three independent ensembles by adding: either only the TOTEM data (as in the MN analysis), or only the ATLAS data, or both sets; (2) in the data reductions to each ensemble, uncertainty regions are evaluated through error propagation from the fit parameters, with 90% CL. We argument that, within the uncertainties, this analytic model corresponding to soft Pomeron dominance, does not seem to be excluded by the complete set of experimental data presently available.

10.1016/j.physletb.2018.04.045

J.C. Jiménez and E.S. Fraga

Physical Review D, vol. 97, Iss. 9

Abstract

We investigate protoneutron star matter using the state-of-the-art perturbative equation of state for cold and dense QCD in the presence of a fixed lepton fraction in which both electrons and neutrinos are included. Besides computing the modifications in the equation of state due to the presence of trapped neutrinos, we show that stable strange quark matter has a more restricted parameter space. We also study the possibility of nucleation of unpaired quark matter in the core of protoneutron stars by matching the lepton-rich QCD pressure onto a hadronic equation of state, namely TM1 with trapped neutrinos. Using the inherent dependence of perturbative QCD on the renormalization scale parameter, we provide a measure of the uncertainty in the observables we compute.

10.1103/PhysRevD.97.094023

Luiz Lopes and Debora Menezes

Journal of Cosmology and Astroparticle Physics, Volume 2018, May 2018

ABSTRACT

We study how the Λ hyperon threshold influences the radius of the canonical 1.4 M⊙ neutron star in the light of the measurements found in the recent literature. We show that the onset of a new degree of freedom not only causes the well known reduction of the maximum mass, but also compacts the neutron stars with high central density. With the help of the strange mesons phgr and σ*, we show that it is possible to simulate very compact neutron stars keeping realistic hyperon potentials, UΛ(n0)= −28 MeV and UΛΛ(n0/5) in agreement with recents measurements. In the end we generalize these results showing that the onset of a yet not known dark matter particle with mass of 1.04 GeV is able to produce simultaneously a 2 M⊙ neutron star and a canonical one with a radius of only 11.62 km.

DOI: 10.1088/1475-7516/2018/05/038

Thamirys de Oliveira, Débora P. Menezes, Marcus B. Pinto, and Francesca Gulminelli

Phys. Rev. C 97, 055205

ABSTRACT

We compare relativistic mean-field models with their low density expansion counterparts used to mimic nonrelativistic models by consistently expanding the baryonic scalar density in powers of the baryonic number density up to O(13/3), which goes two orders beyond the order considered in previous works. We show that, due to the nontrivial density dependence of the Dirac mass, the convergence of the expansion is very slow, and the validity of the nonrelativistic approximation is questionable even at subsaturation densities. In order to analyze the roles played by strangeness and isospin we consider n−Λ and n−p matter separately. Our results indicate that these degrees of freedom play quite different roles in the expansion mechanism and n−Λ matter can be better described by low density expansions than n−p matter in general.

DOI:10.1103/PhysRevC.97.055205

G. S. Denicol; J. Noronha

PHYSICAL REVIEW D, v. 97, p. 056021, 2018

Abstract

We find the general analytical solution of the viscous relativistic hydrodynamic equations (in the absence of bulk viscosity and chemical potential) for a Bjorken expanding fluid with an ideal gas equation of state and a constant shear viscosity relaxation time. We analytically determine the hydrodynamic attractor of this fluid and discuss its properties. We show for the first time that the slow-roll expansion, a commonly used approach to characterize the attractor, diverges. This is shown to hold also in a conformal plasma. The gradient expansion is found to converge in an example where causality and stability are violated.

10.1103/PhysRevD.97.056021

Fábio L. Braghin

Eur. Phys. J. A (2018) 54: 45

Abstract

An effective model with pions and constituent quarks in the presence of a weak external background electromagnetic field is derived by starting from a dressed one gluon exchange quark-quark interaction. By applying the auxiliary field and background field methods, the structureless pion limit is considered to extract effective pion and constituent quark couplings in the presence of a weak magnetic field. The leading terms of a large quark and gluon masses expansion are obtained by resolving effective coupling constants which turn out to depend on a weak magnetic field. Two pion field definitions are considered for that. Several relations between the effective coupling constants and parameters can be derived exactly or in the limit of very large quark mass at zero and weak constant magnetic field. Among these ratios, the Gell-Mann-Oakes-Renner and the quark level Goldberger-Treiman relations are obtained. In addition to that, in the pion sector, the leading terms of Chiral Perturbation Theory coupled to the electromagnetic field are recovered. Some numerical estimates are provided for the effective coupling constants and parameters.

10.1140/epja/i2018-12485-6