Nuclear Theory·nucl-th

Wednesday·March 25, 2015

13 papers—9 primary·4 cross-listed

01
[Submitted on 24 Mar 2015]
Low mass enhanced probability of pion in hadronic matter due to its Landau cut contributions
Sabyasachi Ghosh🇧🇷
In the real-time thermal field theory, the pion self-energy at finite temperature and density is evaluated where the different mesonic and baryonic loops are considered. The interactions of pion with the other mesons and baryons in the medium are governed by the effective hadronic Lagrangian densities whose effective strength of coupling constants have been determined from the experimental decay widths of the mesons and baryons. The detail branch cut structures of these different mesonic and baryonic loops are analyzed. The Landau cut contributions of different baryon and meson loops become only relevant around the pion pole and it is completely appeared in presence of medium. The in-medium spectral function of pion has been plotted for different values of temperature, baryon chemical potential as well as three momentum of the pion. A noticeable low mass probability in pion spectral function promise to contribute in the low mass dilepton enhancement via indirect modification of $ρ$ self-energy for $π π$ loop.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1503.06925 [pdf]
J.Phys.G(2014)·4 citations
02
[Submitted on 24 Mar 2015]
The nucleon thermal width due to pion-baryon loops and its contribution in Shear viscosity
Sabyasachi Ghosh🇧🇷
In the real-time thermal field theory, the standard expression of shear viscosity for the nucleonic constituents is derived from the two point function of nucleonic viscous stress tensors at finite temperature and density. The finite thermal width or Landau damping is traditionally included in the nucleon propagators. This thermal width is calculated from the in-medium self-energy of nucleon for different possible pion-baryon loops. The dynamical part of nucleon-pion-baryon interactions are taken care by the effective Lagrangian densities of standard hadronic model. The shear viscosity to entropy density ratio of nucleonic component decreases with the temperature and increases with the nucleon chemical potential. However, adding the contribution of pionic component, total viscosity to entropy density ratio also reduces with the nucleon chemical potential when the mixing effect between pion and nucleon components in the mixed gas is considered. Within the hadronic domain, viscosity to entropy density ratio of the nuclear matter is gradually reducing as temperature and nucleon chemical potential are growing up and therefore the nuclear matter is approaching toward the (nearly) perfect fluid nature.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1503.06927 [pdf]
PRC(2014)·41 citations
03
[Submitted on 24 Mar 2015]
Nuclear modification and azimuthal anisotropy of D mesons produced in relativistic heavy ion collision
Mohammed Younus🇮🇳
In this paper we present a phenomenological treatment of charm quark energy loss before fragmenting into D mesons and calculate nuclear modification factor, ' $R_{AA}$ ' and azimuthal anisotropy, ' $v_{2}$ ' of D mesons for lead on lead collision at LHC energy of $s$ =2.76 A TeV.
Comments:
13 pages 5 plots in 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1503.06936 [pdf]
2 citations
04
[Submitted on 24 Mar 2015]
A comparative analysis of in-medium spectral functions for $N (940)$ and $N^{*} (1535)$ in real-time thermal field theory
Sabyasachi Ghosh
In the real-time thermal field theory, the nucleon self-energy at finite temperature and density is evaluated where an extensive set of pion-baryon ( $π B$ ) loops are considered. On the other side the in-medium self-energy of $N^{*} (1535)$ for $π N$ and $η N$ loops is also determined in the same framework. The detail branch cut structures for these different $π B$ loops for nucleon $N (940)$ and $π N$ , $η N$ loops for $N^{*} (1535)$ are addressed. Using the total self-energy of $N (940)$ and $N^{*} (1535)$ , which contain the contributions of their corresponding loop diagrams, the complete structures of their in-medium spectral functions have been obtained. The Landau and unitary cut contributions provide two separate peak structures in the nucleon spectral function while $N^{*} (1535)$ has single peak structure in its unitary cuts. At high temperature, the peak structures of both at their individual poles are attenuated while at high density Landau peak structure of nucleon is completely suppressed and its unitary peak structure is tending to be shifted towards the melted peak of $N^{*} (1535)$ . The non-trivial modifications of these chiral partners may indicate some association of chiral symmetry restoration.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1503.06941 [pdf]
Braz.J.Phys.(2014)·3 citations
05
[Submitted on 24 Mar 2015]
Energy Resolution with the Lorentz integral transform
Winfried Leidemann
A brief outline of the Lorentz Integral Transform (LIT) method is given. The method is well established and allows to treat reactions into the many-body continuum with bound-state like techniques. The energy resolution that can be achieved is studied by means of a simple two-body reaction. From the discussion it will become clear that the LIT method is an approach with a controlled resolution and that there is no principle problem to even resolve narrow resonances in the many-body continuum. As an example the isoscalar monopole resonance of 4He is considered. The importance of the choice of a proper basis for the expansion of the LIT states is pointed out. Employing such a basis a width of 180(70) keV is found for the 4He isoscalar monopole resonance when using a simple central nucleon-nucleon potential model.
Comments:
8 pages, 6 figures, some additional explanations
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1503.06975 [pdf]
PRC(2015)·15 citations
06
[Submitted on 24 Mar 2015]
Hadronic "flow" in p--Pb collisions at the Large Hadron Collider?
You Zhou🇨🇳 · Xiangrong Zhu🇨🇳 · Pengfei Li🇨🇳 · Huichao Song🇨🇳
Using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, we investigate azimuthal correlations in p--Pb collisions at $s_{_{NN}} = 5.02$ TeV. Comparison with the experimental data shows that UrQMD can not reproduce the multiplicity dependence of 2- and 4-particle cumulants, especially the transition from positive to negative values of $c_{2} {4}$ in high multiplicity events, which has been taken as experimental evidence of collectivity in p--Pb collisions. Meanwhile, UrQMD can not qualitatively describe the differential elliptic flow, $v_{2} (p_{T})$ , of all charged hadrons at various multiplicity classes. These discrepancies show that the simulated hadronic p--Pb systems can not generate enough collective flow as observed in experiment, the associated hadron emissions are largely influenced by non-flow effects. However, the characteristic $v_{2} (p_{T})$ mass-ordering of pions, kaons and protons is observed in UrQMD, which is the consequence of hadronic interactions and not necessarily associated with strong fluid-like expansions.
Comments:
12 pages 9 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1503.06986 [pdf]
PRC(2015)·65 citations
07
[Submitted on 24 Mar 2015]
Generalized nuclear contacts and the nucleon's momentum distributions
Ronen Weiss · Betzalel Bazak · Nir Barnea
The general nuclear contact matrices are defined, taking into consideration all partial waves and finite-range interactions, extending Tan's work for the zero range model. The properties of these matrices are discussed and the relations between the contacts and the one-nucleon and two-nucleon momentum distributions are derived. Using these relations, a new asymptotic connection between the one-nucleon and two-nucleon momentum distributions, describing the two-body short-range correlations in nuclei, is obtained. Using available numerical data, we extract few connections between the different contacts and verify their relations to the momentum distributions. The numerical data also allows us to identify the main nucleon momentum range affected by two-body short-range correlations. Utilizing these relations and the numerical data, we also verify a previous independent prediction connecting between the Levinger constant and the contacts. This work provides an important indication for the relevance of the contact formalism to nuclear systems, and should open the path for revealing more useful relations between the contacts and interesting quantities of nuclei and nuclear matter.
Comments:
10 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas)
arXiv:
1503.07047 [pdf]
PRC(2015)·94 citations
08
[Submitted on 24 Mar 2015]
Ginzburg-Landau free energy of crystalline color superconductors: A matrix formalism from solid-state physics
Gaoqing Cao🇨🇳 · Lianyi He🇺🇸
The Ginzburg-Landau (GL) free energy of crystalline color superconductors is important for understanding the nature of the phase transition to the normal quark matter and predicting the preferred crystal structure. So far the GL free energy at zero temperature has only been evaluated up to the sixth order in the condensate. To give quantitative reliable predictions we need to evaluate the higher-order terms. In this work, we present a new derivation of the GL free energy by using the discrete Bloch representation of the fermion field. This derivation introduces a simple matrix formalism without any momentum constraint, which may enable us to calculate the GL free energy to arbitrary order by using a computer.
Comments:
Published version, references added
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); Superconductivity (cond-mat.supr-con); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1503.07124 [pdf]
Commun.Theor.Phys.(2015)·1 citation
09
[Submitted on 24 Mar 2015]
Infrared length scale and extrapolations for the no-core shell model
K. A. Wendt · C. Forssén · T. Papenbrock · D. Sääf
We precisely determine the infrared (IR) length scale of the no-core shell model (NCSM). In the NCSM, the $A$ -body Hilbert space is truncated by the total energy, and the IR length can be determined by equating the intrinsic kinetic energy of $A$ nucleons in the NCSM space to that of $A$ nucleons in a $3 (A - 1)$ -dimensional hyper-radial well with a Dirichlet boundary condition for the hyper radius. We demonstrate that this procedure indeed yields a very precise IR length by performing large-scale NCSM calculations for $^{6}$ Li. We apply our result and perform accurate IR extrapolations for bound states of $^{4}$ He, $^{6}$ He, $^{6}$ Li, $^{7}$ Li. We also attempt to extrapolate NCSM results for $^{10}$ B and $^{16}$ O with bare interactions from chiral effective field theory over tens of MeV.
Comments:
8 pages, 4 figures. Updated to address issues fixed during publication. We have prepared a python (v2.7) script that will compute the IR scales (both full scale and intrinsic scale). This script depends only on numpy and scipy and can be found at http://github.com/KyleWendt/ncsm_ho_ir_scale
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1503.07144 [pdf]
PRC(2015)·80 citations

Affiliations

first authorsco-authorsvia INSPIRE