Nuclear Theory·nucl-th

Friday·February 10, 2017

6 papers—4 primary·2 cross-listed

01
[Submitted on 9 Feb 2017]
Compton scattering off proton in the third resonance region
Xu Cao🇩🇪 · H. Lenske🇩🇪
Compton scattering off the proton in the third resonance region is analyzed for the first time, owing to the full combined analysis of pion- and photo-induced reactions in a coupled-channel effective Lagrangian model with K-matrix approximation. Two isospin $I = 3/2$ resonances $D_{33} (1700)$ and $F_{35} (1930)$ are found to be essential in the range of 1.6 - 1.8 GeV. The recent beam asymmetry data of Compton scattering from the GRAAL facility are used to determine the helicity couplings of these resonances, and strong constraints are coming also from $π N$ and $K Σ$ photoproduction data. The possible spin and parity of new narrow resonances is discussed.
Comments:
7 pages, 2 figs, 2 tabs, publish version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1702.02692 [pdf]
PLB(2017)·5 citations
02
[Submitted on 9 Feb 2017]
Gamow-Teller transitions and proton-neutron pair correlation in $N = Z =$ odd $p$ -shell nuclei
Hiroyuki Morita · Yoshiko Kanada-En'yo
We have studied the Gamow-Teller (GT) transitions from $N = Z + 2$ neighbors to $N = Z =$ odd nuclei in $p$ -shell region by using isospin-projected and $β γ$ -constraint antisymmetrized molecular dynamics combined with generator coordinate method. The calculated GT transition strengths from $0^{+} 1$ states to $1^{+} 0$ states such as $^{6} He (0_{1}^{+} 1) \to^{6} Li (1_{1}^{+} 0)$ , $^{10} Be (0_{1}^{+} 1) \to^{10} B (1_{1}^{+} 0)$ , and $^{14} C (0_{1}^{+} 1) \to^{14} N (1_{2}^{+} 0)$ exhaust more than 50\% of the sum rule. These $N = Z + 2$ initial states and $N = Z =$ odd final states are found to dominantly have $S = 0, T = 1$ $nn$ pairs and $S = 1, T = 0$ $p n$ pairs, respectively. Based on two-nucleon ( $N N$ ) pair picture, we can understand the concentration of the GT strengths as the spin-isospin-flip transition $nn (S = 0, T = 1) \to p n (S = 1, T = 0)$ in $L S$ -coupling scheme. The GT transition can be a good probe to identify the spin-isospin partner states with $nn$ pairs and $p n$ pairs of $N = Z + 2$ and $N = Z =$ odd nuclei, respectively.
Comments:
21 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1702.02727 [pdf]
PRC(2017)·7 citations
03
[Submitted on 9 Feb 2017]
Neutron star crusts from mean field models constrained by chiral effective field theory
Yeunhwan Lim🇺🇸 · Jeremy W. Holt🇺🇸
We investigate the structure of neutron star crusts, including the crust-core boundary, based on new Skyrme mean field models constrained by the bulk-matter equation of state from chiral effective field theory and the ground-state energies of doubly-magic nuclei. Nuclear pasta phases are studied using both the liquid drop model as well as the Thomas-Fermi approximation. We compare the energy per nucleon for each geometry (spherical nuclei, cylindrical nuclei, nuclear slabs, cylindrical holes, and spherical holes) to obtain the ground state phase as a function of density. We find that the size of the Wigner-Seitz cell depends strongly on the model parameters, especially the coefficients of the density gradient interaction terms. We employ also the thermodynamic instability method to check the validity of the numerical solutions based on energy comparisons.
Comments:
13 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1702.02898 [pdf]
PRC(2017)·73 citations
04
[Submitted on 9 Feb 2017]
Investigating the temperature dependence of the specific shear viscosity of QCD matter with dilepton radiation
Gojko Vujanovic🇺🇸 · Gabriel S. Denicol🇧🇷 · Matthew Luzum🇧🇷 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
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.
Comments:
25 pages, 20 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1702.02941 [pdf]
PRC(2018)·25 citations
05
[Submitted on 9 Feb 2017] (cross-list from hep-ph)
Pressure of a weakly magnetized hot and dense deconfined QCD matter in one-loop hard-thermal-loop perturbation theory
Aritra Bandyopadhyay🇮🇳 · Bithika Karmakar🇮🇳 · Najmul Haque🇮🇳 · Munshi G. Mustafa🇮🇳
We consider our recently obtained general structure of two point (self-energy and propagator) functions of quarks and gluons in a nontrivial background like a heat bath and an external magnetic field. Based on this, here we have computed free energy and pressure of quarks and gluons for a magnetized hot and dense deconfined QCD matter in weak field approximation. For heat bath we have used hard thermal loop perturbation theory (HTLpt) in presence of finite chemical potential. For weak field approximations we have obtained the pressure of QCD matter, both with and without the high temperature expansion. The results with high $T$ expansions are completely analytic and gauge independent but depends on the renormalization scale in addition to the temperature, chemical potential and the external magnetic field. We also discuss the modification of QCD Debye mass of such matter for an arbitrary magnetic field. Analytic expressions for Debye mass are also obtained for both strong and weak field approximation. It is found to exhibit some interesting features depending upon the three different scales, i.e, the quark mass, temperature and the strength of the magnetic field. The various divergences appearing in the quark and gluon free energies are regulated through appropriate counter terms. In weak field approximation, the low temperature behavior of the pressure is found to strongly depend on the magnetic field than that at high temperature. We also discuss the specific problem with one-loop HTLpt associated with the over-counting of certain orders in coupling.
Comments:
65 pages, 8 figures; Published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1702.02875 [pdf]
PRD(2019)·73 citations
06
[Submitted on 9 Feb 2017] (cross-list from hep-lat)
Double- $β$ Decay Matrix Elements from Lattice Quantum Chromodynamics
Brian C. Tiburzi🇺🇸 · Michael L. Wagman🇺🇸 · Frank Winter🇺🇸 · Emmanuel Chang🇺🇸 · Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸 · Martin J. Savage🇺🇸 · Phiala E. Shanahan🇺🇸
A lattice quantum chromodynamics (LQCD) calculation of the nuclear matrix element relevant to the $nn \to pp ee ν_{e} ν_{e}$ transition is described in detail, expanding on the results presented in Ref. [1]. This matrix element, which involves two insertions of the weak axial current, is an important input for phenomenological determinations of double- $β$ decay rates of nuclei. From this exploratory study, performed using unphysical values of the quark masses, the long-distance deuteron-pole contribution to the matrix element is separated from shorter-distance hadronic contributions. This polarizability, which is only accessible in double-weak processes, cannot be constrained from single- $β$ decay of nuclei, and is found to be smaller than the long-distance contributions in this calculation, but non-negligible. In this work, technical aspects of the LQCD calculations, and of the relevant formalism in the pionless effective field theory, are described. Further calculations of the isotensor axial polarizability, in particular near and at the physical values of the light-quark masses, are required for precise determinations of both two-neutrino and neutrinoless double- $β$ decay rates in heavy nuclei.
Comments:
30 pages, 9 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1702.02929 [pdf]
PRD(2017)·84 citations

Affiliations

first authorsco-authorsvia INSPIRE

Compton scattering off proton in the third resonance region

Gamow-Teller transitions and proton-neutron pair correlation in N=Z= odd p-shell nuclei

Neutron star crusts from mean field models constrained by chiral effective field theory

Investigating the temperature dependence of the specific shear viscosity of QCD matter with dilepton radiation

Pressure of a weakly magnetized hot and dense deconfined QCD matter in one-loop hard-thermal-loop perturbation theory

Double-β Decay Matrix Elements from Lattice Quantum Chromodynamics

Affiliations

Gamow-Teller transitions and proton-neutron pair correlation in $N = Z =$ odd $p$ -shell nuclei

Double- $β$ Decay Matrix Elements from Lattice Quantum Chromodynamics