Nuclear Theory·nucl-th

Wednesday·March 2, 2016

7 papers—5 primary·2 cross-listed

01
[Submitted on 1 Mar 2016]
Nuclear medium effects in $F_{2 A}^{E M} (x, Q^{2})$ and $F_{2 A}^{W e ak} (x, Q^{2})$ structure functions
H. Haider🇮🇳 · F. Zaidi🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳 · I. Ruiz Simo🇪🇸
Recent phenomenological analysis of experimental data on DIS processes induced by charged leptons and neutrinos/antineutrinos beams on nuclear targets by CTEQ collaboration has confirmed the observation of CCFR and NuTeV collaborations, that weak structure function $F_{2 A}^{W e ak} (x, Q^{2})$ is different from electromagnetic structure function $F_{2 A}^{E M} (x, Q^{2})$ in a nucleus like iron, specially in the region of low $x$ and $Q^{2}$ . In view of this observation we have made a study of nuclear medium effects on $F_{2 A}^{W e ak} (x, Q^{2})$ and $F_{2 A}^{E M} (x, Q^{2})$ for a wide range of $x$ and $Q^{2}$ using a microscopic nuclear model. We have considered Fermi motion, binding energy, nucleon correlations, mesonic contributions from pion and rho mesons and shadowing effects to incorporate nuclear medium effects. The calculations are performed in a local density approximation using a relativistic nucleon spectral function which includes nucleon correlations. The numerical results in the case of iron nucleus are compared with the experimental data.
Comments:
17 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.00164 [pdf]
NPA(2016)·32 citations
02
[Submitted on 1 Mar 2016]
Phase diagram of the two-fluid Lipkin model: a butterfly catastrophe
J.E. García-Ramos · P. Pérez-Fernandez · J.M Arias · E. Freire
Background: In the last few decades quantum phase transitions have been of great interest in Nuclear Physics. In this context, two-fluid algebraic models are ideal systems to study how the concept of quantum phase transition evolves when moving into more complex systems, but the number of publications along this line has been scarce up to now. Purpose: We intend to determine the phase diagram of a two-fluid Lipkin model, that resembles the nuclear proton-neutron interacting boson model Hamiltonian, using both numerical results and analytic tools, i.e., catastrophe theory, and to compare the mean-field results with exact diagonalizations for large systems. Method: The mean-field energy surface of a consistent-Q-like two-fluid Lipkin Hamiltonian is studied and compared with exact results coming from a direct diagonalization. The mean-field results are analyzed using the framework of catastrophe theory. Results: The phase diagram of the model is obtained and the order of the different phase-transition lines and surfaces is determined using a catastrophe theory analysis. Conclusions: There are two first order surfaces in the phase diagram, one separating the spherical and the deformed shapes, while the other separates two different deformed phases. A second order line, where the later surfaces merge, is found. This line finishes in a transition point with a divergence in the second order derivative of the energy that corresponds to a tricritical point in the language of the Ginzburg-Landau theory for phase transitions.
Comments:
Accepted in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.00179 [pdf]
PRC(2016)·11 citations
03
[Submitted on 1 Mar 2016]
A nonstiff solution for the stochastic neutron point kinetics equations
Milena Wollmann da Silva · Richard Vasques · Bardo E.J. Bodmann · Marco Tullio Vilhena
We propose an approach to solve the stochastic neutron point kinetics equations using an adaptation of the diagonalization-decomposition method (DDM). This new approach (Double-DDM) yields a nonstiff solution for the stochastic formulation, allowing the calculation of the neutron and precursor densities at any time of interest without the need of using progressive time steps. We use Double-DDM to compute results for stochastic problems with constant, linear, and sinusoidal reactivities. We show that these results strongly agree with those obtained by other approaches established in the literature. We also compute and analyze the first four statistical moments of the solutions.
Comments:
14 pages; 3 figures; 7 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.00195 [pdf]
Annals Nucl.Energy(2016)·0 citations
04
[Submitted on 1 Mar 2016]
Production and Interactions of Hyperons and Hypernuclei
Horst Lenske🇩🇪 · Xu Cao🇨🇳 · Madhumita Dhar🇩🇪 · Theodoros Gaitanos🇬🇷 · Radhey Shyam🇮🇳
The production of strangeness on the nucleon and hyperon and hypernuclear production in heavy ion collisions at relativistic energies and in antiproton annihilation on nuclei is discussed. The reaction process is described by transport theory with focus on $S = - 2$ channels and a comparison of different model interactions. The interactions of hyperons in nuclear matter is investigated in a novel SU(3) approach. An outlook to the $S = - 3$ sector and $Ω^{-}$ physics is given.
Comments:
11 pages, 5 figures, In print at JPS/HYP 2015 Conference Proceedings
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1603.00298 [pdf]
JPS Conf.Proc.(2017)·2 citations
05
[Submitted on 1 Mar 2016]
The 3He spectral function in light-front dynamics
Matteo Rinaldi🇮🇹 · Alessio Del Dotto🇮🇹 · Leonid Kaptari🇷🇺 · Emanuele Pace🇮🇹 · Giovanni Salmè🇮🇹 · Sergio Scopetta🇮🇹
A distorted spin-dependent spectral function for 3He is considered for the extraction of the transverse-momentum dependent parton distributions in the neutron from semi-inclusive deep inelastic electron scattering off polarized 3He at finite momentum transfers, where final state interactions are taken into account. The generalization of the analysis to a Poincaré covariant framework within the light-front dynamics is outlined.
Comments:
4 pages, 2 figures, talk given at the 21st International Conference on Few-Body Problems in Physics, Chicago, IL, May 18th-22nd, 2015; EPJ Web of Conference, in press
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1603.00366 [pdf]
EPJ Web Conf.(2016)·1 citation
06
[Submitted on 1 Mar 2016] (cross-list from astro-ph.HE)
Numerically Fitting The Electron Fermi Energy and The Electron Fraction in A Neutron Star
Xing Hu Li · Zhi Fu Gao · Xiang Dong Li · Yan Xu · Pei Wang · Na Wang · Jianping Yuan
Based on the basic definition of Fermi energy of degenerate and relativistic electrons, we obtain a special solution to electron Fermi energy, $E_{F} (e)$ , and express $E_{F} (e)$ as a function of electron fraction, $Y_{e}$ , and matter density, $ρ$ . Several useful analytical formulae for $Y_{e}$ and $ρ$ within classical models and the work of Dutra et al. 2014 (Type-2) in relativistic mean field theory are obtained using numerically fitting. When describing the mean-field Lagrangian, density, we adopt the TMA parameter set, which is remarkably consistent with with the updated astrophysical observations of neutron stars. Due to the importance of the density dependence of the symmetry energy, $S$ , in nuclear astrophysics, a brief discussion on the symmetry parameters $S_{v}$ and $L$ (the slope of $S$ ) is presented. Combining these fit formulae with boundary conditions for different density regions, we can evaluate the value of $E_{F} (e)$ in any given matter density, and obtain a schematic diagram of $E_{F} (e)$ as a continuous function of $ρ$ . Compared with previous study on the electron Fermi energy in other models, our methods of calculating $E_{F} (e)$ are more simple and convenient, and can be universally suitable for the relativistic electron regions in the circumstances of common neutron stars. We have deduced a general expression of $E_{F} (e)$ and $n_{e}$ , which could be used to indirectly test whether one EoS of a NS is correct in our future studies on neutron star matter properties. Since URCA reactions are expected in the center of a massive star due to high-value electron Fermi energy and electron fraction, this study could be useful in the future studies on the NS thermal evolution.
Comments:
30 pages, 14 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1603.00224 [pdf]
11 citations
07
[Submitted on 1 Mar 2016] (cross-list from quant-ph)
Casimir-Polder interaction of neutrons with metal or dielectric surfaces
Valentin Gebhart🇩🇪 · Juliane Klatt🇩🇪 · Gunther Cronenberg🇦🇹 · Hanno Filter🇦🇹 · Stefan Yoshi Buhmann🇩🇪
We predict a repulsive Casimir-Polder-type dispersion interaction between a single neutron and a metal or dielectric surface. We consider a scenario where a single neutron is subject to an external magnetic field. Due to its intrinsic magnetic moment, the neutron then forms a magnetisable two-level system which can exchange virtual photons with a nearby surface. The resulting dispersion interaction between a purely magnetic object (neutron) and a purely electric one (surface) is found to be repulsive, in contrast to the typical attractive interaction between electric objects. Its magnitude is considerably smaller than the standard atom--surface Casimir-Polder force due to the magnetic nature of the interaction and the smallness of the electron-to-neutron mass ratio. Nevertheless, we show that it can be comparable to the gravitational potential of the same surface and should be taken into consideration in future neutron interference experiments.
Comments:
8 pages, 4 figures
Subjects:
Quantum Physics (quant-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1603.00345 [pdf]
New J.Phys.(2021)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Nuclear medium effects in F2AEM​(x,Q2) and F2AWeak​(x,Q2) structure functions

Phase diagram of the two-fluid Lipkin model: a butterfly catastrophe

A nonstiff solution for the stochastic neutron point kinetics equations

Production and Interactions of Hyperons and Hypernuclei

The 3He spectral function in light-front dynamics

Numerically Fitting The Electron Fermi Energy and The Electron Fraction in A Neutron Star

Casimir-Polder interaction of neutrons with metal or dielectric surfaces

Affiliations

Nuclear medium effects in $F_{2 A}^{E M} (x, Q^{2})$ and $F_{2 A}^{W e ak} (x, Q^{2})$ structure functions