Altas Energias

Dumitru, Adrian; Giannini, Andre V.; Luzum, Matthew; Nara, Yasushi

Physics Letters B, Volume 784, p. 417-422

Abstract

Horowitz and Kovchegov have derived a kT-factorization formula for particle production at small x which includes running coupling corrections. We perform a first numerical analysis to confront the theory with data on the energy and centrality dependence of particle multiplicities at midrapidity in high-energy p+A (and A+A) collisions. Moreover, we point out a strikingly different dependence of the multiplicity per participant on Npart in p+Pb vs. Pb+Pb collisions at LHC energies, and argue that the observed behavior follows rather naturally from the convolution of the gluon distributions of an asymmetric vs. symmetric projectile and target.

10.1016/j.physletb.2018.08.028

G.De Conto, A.C.B.Machado, J.P.B.C.de Melo

Physics Letters B, Volume 784, 10 September 2018, Pages 255-260

ABSTRACT

In this paper we present an analytic solution for the mass matrix of the CP-even neutral scalars in the minimal 331 model (m331), identifying the Standard Model Higgs boson and its self-interactions, showing that the m331 can automatically reproduce the Higgs potential of the Standard Model. We also present a method to generate numerical solutions for the quarks and leptons masses and mixings that are compatible with the measured masses, the Cabbibo–Kobayashi–Maskawa (CKM) and Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrices. The method employed here to find these solutions can be adapted to other multi-Higgs models.

DOI:10.1016/j.physletb.2018.07.056

Parada T. P. Hutauruk, Yongseok Oh, and K. Tsushima

Phys. Rev. D 98, 013009

ABSTRACT

Impact of the in-medium modified nucleon weak and electromagnetic form factors on the neutrino mean free path in dense matter is studied by considering both the weak and electromagnetic interactions of neutrinos with the constituents of the matter. A relativistic mean field model and the quark-meson coupling model are respectively adopted for the in-medium effective nucleon mass and nucleon form factors. We find that the cross sections of neutrino scattering in cold nuclear medium decrease when the in-medium modifications of the nucleon weak and electromagnetic form factors are taken into account. This reduction results in the enhancement of the neutrino mean free path, in particular at the baryon density of around a few times of the normal nuclear matter density. The enhancement of the neutrino mean free path is estimated to be about 10%–40% compared with the values obtained without the medium modifications of the nucleon form factors, and the enhancement is expected to accelerate the cooling of neutron stars.

DOI:10.1103/PhysRevD.98.013009

G. VUJANOVIC: G. S. DENICOL; M. LUZUM; S. JEON; C. GALE

PHYSICAL REVIEW C, v. 98, p. 014902, 2018

Abstract

This work reports on investigations of the effects on the evolution of viscous hydrodynamics and on the flow coefficients of thermal dileptons, originating from a temperature-dependent specific shear viscosity η/s(T) at temperatures beyond 180 MeV formed at the Relativistic Heavy-Ion Collider (RHIC). We show that the elliptic flow of thermal dileptons can resolve the magnitude of η/s at the high temperatures, where partonic degrees of freedom become relevant, whereas discriminating between different specific functional forms will likely not be possible at RHIC using this observable.

10.1103/PhysRevC.98.014902

Orlando Oliveira, T. Frederico, W. de Paula, J. P. B. C. de Melo

The European Physical Journal C, July 2018, 78:553

ABSTRACT

The soft gluon limit of the longitudinal part of the quark-gluon vertex is studied by resorting to non-perturbative approaches to quantum chromodynamics (QCD). Based on a Slavnov–Taylor identity (STI), the longitudinal form factors is expressed in terms of the quark-ghost kernel, the quark self energy and the quark wave function. An exact relation between the non-vanishing longitudinal form factors is derived for the soft gluon limit and explored to understand the behaviour of the vertex. Within a Ball–Chiu vertex, the form factor  λ1λ1  was analysed using recent lattice simulations for full QCD for the soft gluon limit. The lattice data shows that the gluon propagator resumes the momentum dependence of such component of the vertex. This connection is understood via a fully dressed one-loop Bethe–Salpeter equation. The behaviour of the remaining longitudinal form factors  λ2(p2)λ2(p2)  and  λ3(p2)λ3(p2)  is investigated combining both the information of lattice simulations and the derived relations based on the STI.

DOI:10.1140/epjc/s10052-018-6037-0

Giorgio Torrieri

Phys. Rev. C 98, 014901

Abstract

I argue that, because of the peculiar properties of the η’ meson, it is a promising probe of chiral dynamics. In particular, I show that a rotating gluon-dominated plasma might lead to an enhanced production of η’ with respect to statistical model expectations. The presence of a strong topological susceptibility might give a similar effect. In both cases, unlike the statistical model, I expect a nontrivial dependence on event geometry, such as initial volume and impact parameter. Hence, an observation of η’/π ratio depending strongly on impact parameter might be a good indication of chiral effects, either from vorticity or topological phases of QCD.

10.1103/PhysRevC.98.014901

Fernando G. Gardim, Frédérique Grassi, Pedro Ishida, Matthew Luzum, Pablo S. Magalhães, and Jacquelyn Noronha-Hostler

Phys. Rev. C 97, 064919

Abstract

An open question in the field of heavy-ion collisions is to what extent the size of initial inhomogeneities in the system affects measured observables. Here we present a method to smooth out these inhomogeneities with minimal effect on global properties, to quantify the effect of short-range features of the initial state. We show a comparison of hydrodynamic predictions with original and smoothened initial conditions for four models of initial conditions and various observables. Integrated observables (integrated vn, scaled vn distributions, normalized symmetric cumulants, event-plane correlations) as well as most differential observables [vn(pT) ] show little dependence on the inhomogeneity sizes and instead are sensitive only to the largest-scale geometric structure. However, other differential observables such as the flow factorization ratio and subleading principal components are more sensitive to the granularity and could be a good tool to probe the short-scale dynamics of the initial stages of a heavy-ion collision, which are not currently well understood.

10.1103/PhysRevC.97.064919

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