Nuclear Theory·nucl-th
13 papers—7 primary·6 cross-listed
[Submitted on 23 May 2015]
I describe how nuclear structure can be predicted from lattice QCD through low-energy effective field theories, using as an example a world simulation with relatively heavy up and down quarks.
[Submitted on 23 May 2015]
Z. Lin🇺🇸 · C. J. Horowitz🇺🇸
Background: The ground state neutron density of a medium mass nucleus contains fundamental nuclear structure information and is at present relatively poorly known. Purpose: We explore if parity violating elastic electron scattering can provide a feasible and model independent way to determine not just the neutron radius but the full radial shape of the neutron density and the weak charge density of a nucleus. Methods: We expand the weak charge density of Ca in a model independent Fourier Bessel series and calculate the statistical errors in the individual coefficients that might be obtainable in a model parity violating electron scattering experiment. Results: We find that it is feasible to determine roughly six Fourier Bessel coefficients of the weak charge density of 48Ca within a reasonable amount of beam time. However, it would likely be much harder to determine the full weak density of a significantly heavier nucleus such as 208Pb. Conclusions: Parity violating elastic electron scattering can determine the full weak charge density of a medium mass nucleus in a model independent way. This weak density contains fundamental information on the size, surface thickness, shell oscillations, and saturation density of the neutron distribution in a nucleus. The measured , combined with the previously known charge density , will literally provide a detailed textbook picture of where the neutrons and protons are located in an atomic nucleus.
[Submitted on 24 May 2015]
Li-Ye Xiao🇨🇳 · Xu Cao🇨🇳 · Xian-Hui Zhong🇨🇳
A chiral quark-model approach is adopted to study the and reactions. Good descriptions of the total and differential cross sections and single-polarization observables are obtained from the pion production threshold up to the second resonance region. It is found that (i) the shell resonance , the shell resonances and , and the shell resonance play crucial roles in these two processes. They are responsible for the first, second and third bump structures in the cross sections, respectively. (ii) Furthermore, obvious evidences of and are also found in the reactions. They notably affect the cross sections and the polarization observables from the second resonance region to the third resonance region. (iii) The -channel background plays a crucial role in the reactions. It has strong interferences with the -channel resonances. (iv) The -channel background seems to be needed in the reactions. Including the -channel vector-meson exchange contribution, the descriptions in the energy region MeV are improved significantly. The helicity amplitudes of the main resonances, , , , , and , are extracted and compared with the results from other groups.
[Submitted on 25 May 2015]
In the present paper, the Tsallis statistics in the grand canonical ensemble was reconsidered in a general form. The thermodynamic properties of the nonrelativistic ideal gas of hadrons in the grand canonical ensemble was studied numerically and analytically in a finite volume and the thermodynamic limit. It was proved that the Tsallis statistics in the grand canonical ensemble satisfies the requirements of the equilibrium thermodynamics in the thermodynamic limit if the thermodynamic potential is a homogeneous function of the first order with respect to the extensive variables of state of the system and the entropic variable is an extensive variable of state. The equivalence of canonical, microcanonical and grand canonical ensembles for the nonrelativistic ideal gas of hadrons was demonstrated.
[Submitted on 25 May 2015]
Kazuyuki Ogata · Kazuki Yoshida · Kosho Minomo
The parallel momentum distribution (PMD) of the residual nuclei of the 14O(p,pn)13O and 14O(p,2p)13N reactions at 100 and 200 MeV/nucleon in inverse kinematics is investigated with the framework of the distorted wave impulse approximation. The PMD shows an asymmetric shape characterized by a steep fall-off on the high momentum side and a long-ranged tail on the low momentum side. The former is found to be due to the phase volume effect reflecting the energy and momentum conservation, and the latter is to the momentum shift of the outgoing two nucleons inside an attractive potential caused by the residual nucleus. Dependence of these effects on the nucleon separation energy of the projectile and the incident energy is also discussed.
[Submitted on 19 May 2015]
Boris Tatischeff🇫🇷 · Egle Tomasi-Gustafsson🇫🇷
The possible existence of a () S = 0 meson at M 762 MeV is discussed through a critical analysis of the existing data. Different experimental results are considered and show the possibility that the presence of such meson is not excluded by the data, but may be hidden by more excited mesons at nearby masses.
[Submitted on 25 May 2015]
Debora P. Menezes🇧🇷 · Luiz L. Lopes🇧🇷
We revisit three of the mathematical formalisms used to describe magnetized quark matter in compact objects within the MIT and the Nambu-Jona-Lasinio models and then compare their results. The tree formalisms are based on 1) isotropic equations of state, 2) anisotropic equations of state with different parallel and perpendicular pressures and 3) the assumption of a chaotic field approximation that results in a truly isotropic equation of state. We have seen that the magnetization obtained with both models is very different: while the MIT model produces well-behaved curves that are always positive for large magnetic fields, the NJL model yields a magnetization with lots of spikes and negative values. This fact has strong consequences on the results based on the existence of anisotropic equations of state. We have also seen that, while the isotropic formalism results in maximum stellar masses that increase considerably when the magnetic fields increase, maximum masses obtained with the chaotic field approximation never vary more than 5.5. The effect of the magnetic field on the radii is opposed in the MIT and NJL models: with both formalisms, isotropic and chaotic field approximation, for a fixed mass, the radii increase with the increase of the magnetic field in the MIT bag model and decrease in the NJL, the radii of quark stars described by the NJL model being smaller than the ones described by the MIT model.
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