Nuclear Theory·nucl-th

Monday·December 8, 2014

10 papers—8 primary·2 cross-listed

01
[Submitted on 4 Dec 2014]
Meson-exchange currents and quasielastic predictions for charged-current neutrino-12C scattering in the superscaling approach
G. D. Megias🇪🇸 · T. W. Donnelly🇺🇸 · O. Moreno🇺🇸 · C. F. Williamson🇺🇸 · J. A. Caballero🇪🇸 · R. Gonzalez-Jimenez🇪🇸 · A. De Pace🇮🇹 · M. B. Barbaro🇮🇹 · W. M. Alberico🇮🇹 · M. Nardi🇮🇹 · J. E. Amaro🇪🇸
We evaluate and discuss the impact of meson-exchange currents (MECs) on charged-current quasielastic neutrino cross sections. We consider the nuclear transverse response arising from two-particle two-hole states excited by the action of electromagnetic, purely isovector meson-exchange currents in a fully relativistic framework based on the work by the Torino Collaboration [A. D. Pace, M. Nardi, W. M. Alberico, T. W. Donnelly, and A. Molinari, Nucl. Phys. A726, 303 (2003)]. An accurate parametrization of this MEC response as a function of the momentum and energy transfers involved is presented. Results of neutrino-nucleus cross sections using this MEC parametrization together with a recent scaling approach for the one-particle one-hole contributions (named SuSAv2) are compared with experimental data (MiniBooNE, MINERvA, NOMAD and T2K Collaborations).
Comments:
16 pages, 19 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1412.1822 [pdf]
PRD(2015)·110 citations
02
[Submitted on 5 Dec 2014]
Hidden Color and the $b_{1}$ structure function of the deuteron
Gerald A. Miller🇺🇸
The $b_{1}$ structure function is an observable feature of a spin-1 system sensitive to non-nucleonic components of the target nuclear wave function. A simple model for hidden-color, six-quark configurations is proposed and found to give substantial contributions for values of $x > 0.2$ . Good agreement with Hermes data is obtained. Predictions are made for an upcoming JLab experiment.
Comments:
6 pages, 2 figures. This is the written version of a talk presented at the Light Cone 2014 Conference held at North Carolina State Univ. May 26-30
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1412.1864 [pdf]
Few Body Syst.(2015)·2 citations
03
[Submitted on 5 Dec 2014]
Partial wave decomposition of the N3LO equation of state
D. Davesne🇫🇷 · J. Meyer🇫🇷 · A. Pastore🇧🇪 · J. Navarro🇪🇸
By means of a partial wave decomposition, we separate their contributions to the equation of state of symmetric nuclear matter for the N3LO pseudo-potential. In particular, we show that although both the tensor and the spin-orbit terms do not contribute to the equation of state, they give a non-vanishing contribution to the separate (JLS) channels.
Comments:
Invited contribution for XXI Nuclear Physics Workshop 'Marie and Pierre Curie' Kazimierz Dolny, Poland 2014
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1412.1934 [pdf]
Phys.Scripta(2015)·14 citations
04
[Submitted on 5 Dec 2014]
A coarse-graining approach for dilepton production at SPS energies
Stephan Endres🇩🇪 · Hendrik van Hees🇩🇪 · Janus Weil🇩🇪 · Marcus Bleicher🇩🇪
Coarse-grained output from transport calculations is used to determine thermal dilepton emission rates by applying medium-modified spectral functions from thermal quantum field theoretical models. By averaging over an ensemble of events generated with the UrQMD transport model, we extract the local thermodynamic properties at each time step of the calculation. With an equation of state the temperature $T$ and chemical potential $μ_{B}$ can be determined. The approach goes beyond simplified fireball models of the bulk-medium evolution by treating the full (3+1)-dimensional expansion of the system with realistic time and density profiles. For the calculation of thermal dilepton rates we use the in-medium spectral function of the $ρ$ meson developed by Rapp and Wambach and consider thermal QGP and multi-pion contributions as well. The approach is applied to the evaluation of dimuon production in In+In collisions at top SPS energy. Comparison to the experimental results of the NA60 experiment shows good agreement of this ansatz. We find that the experimentally observed low-mass dilepton excess in the mass region from 0.2 to 0.6 GeV can be explained by a broadening of the $ρ$ spectral function with a small mass shift. In contrast, the intermediate mass region ( $M > 1.5$ GeV) is dominated by a contribution from the quark-gluon plasma. These findings agree with previous calculations with fireball parametrizations. This agreement in spite of differences in the reaction dynamics between both approaches indicates that the time-integrated dilepton spectra are not very sensitive to details of the space-time evolution of the collision.
Comments:
15 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1412.1965 [pdf]
PRC(2015)·49 citations
05
[Submitted on 5 Dec 2014]
Monopole giant resonance in $^{100 - 132}$ Sn, $^{144}$ Sm and $^{208}$ Pb
J. Kvasil · D. Bozhik · A. Repko · P.-G. Reinhard · V.O. Nesterenko · W. Kleinig
The isoscalar giant monopole resonance (GMR) in spherical nuclei $^{100 - 132}$ Sn, $^{144}$ Sm, and $^{208}$ Pb is investigated within the Skyrme random-phase-approximation (RPA) for a variety of Skyrme forces and different pairing options. The calculated GMR strength functions are directly compared to the available experimental distributions. It is shown that, in accordance to results of other groups, description of GMR in Sn and heavier Sm/Pb nuclei needs different values of the nuclear incompressibilty, $K \approx$ 200 or 230 MeV, respectively. Thus none from the used Skyrme forces is able to describe GMR in these nuclei simultaneously. The GMR peak energy in open-shell $^{120}$ Sn is found to depend on the isoscalar effective mass, which might be partly used for a solution of the above problem. Some important aspects of the problem (discrepancies of available experimental data, proper treatment of the volume and surface compression in finite nuclei, etc) are briefly discussed.
Comments:
6 pages, 3 figures, submitted to Phys. Scr. (Proceed. of XXI Nuclear Physics Workshop, 23-28.09.2014, Kazimierz Dolny, Poland)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1412.1997 [pdf]
Phys.Scripta(2015)·4 citations
06
[Submitted on 5 Dec 2014]
A self-consistent study of multipole response in neutron-rich nuclei using a modified realistic potential
D. Bianco · F. Knapp · N. Lo Iudice · P. Vesely · F. Andreozzi · G. De Gregorio · A. Porrino
The multipole response of neutron rich O and Sn isotopes is computed in Tamm-Dancoff and random-phase approximations using the canonical Hartree-Fock-Bogoliubov quasi-particle basis. The calculations are performed using an intrinsic Hamiltonian composed of a $V_{l o w k}$ potential, deduced from the CD-Bonn nucleon-nucleon interaction, corrected with phenomenological density dependent and spin-orbit terms. The effect of these two pieces on energies and multipole responses is discussed. The problem of removing the spurious admixtures induced by the center of mass motion and by the violation of the number of particles is investigated. The differences between the two theoretical approaches are discussed quantitatively. Attention is then focused on the dipole strength distribution, including the low-lying transitions associated to the pygmy resonance. Monopole and quadrupole responses are also briefly investigated. A detailed comparison with the available experimental spectra contributes to clarify the extent of validity of the two self-consistent approaches.
Comments:
24 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1412.2004 [pdf]
J.Phys.G(2014)·27 citations
07
[Submitted on 5 Dec 2014]
Cooper-Frye Negative Contributions in a Coarse-Grained Transport Approach
D. Oliinychenko🇩🇪 · P. Huovinen🇩🇪 · H. Petersen🇩🇪
Many models of heavy ion collisions employ relativistic hydrodynamics to describe the system evolution at high densities. The Cooper-Frye formula is applied in most of these models to turn the hydrodynamical fields into particles. However, the number of particles obtained from the Cooper-Frye formula is not always positive-definite. Physically negative contributions of the Cooper-Frye formula are particles that stream backwards into the hydrodynamical region. We quantify the Cooper-Frye negative contributions in a coarse-grained transport approach, which allows to compare them to the actual number of underlying particles crossing the transition hypersurface. It is found that the number of underlying inward crossings is much smaller than the one the Cooper-Frye formula gives under the assumption of equilibrium distribution functions. The magnitude of Cooper-Frye negative contributions is also investigated as a function of hadron mass, collision energy in the range $E_{lab} = 5 - 160 A$ GeV, and collision centrality. The largest negative contributions we find are around 13% for the pion yield at midrapidity at $E_{lab} = 20 A$ GeV collisions.
Comments:
Proceedings of FAIRNESS 2014 conference
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1412.2020 [pdf]
J.Phys.Conf.Ser.(2015)·4 citations
08
[Submitted on 5 Dec 2014]
Unitary neutron matter in the on-shell limit
Enrique Ruiz Arriola · Sergio Szpigel · Varese Salvador Timoteo
We compute the Bertsch parameter for neutron matter by using nucleon-nucleon interactions that are fully diagonal in momentum space. We analyze the on-shell limit with the similarity renormalization group and compare the results for a simple separable toy model to realistic calculations with high precision $N N$ potentials.
Comments:
7 pages, 5 figures, Talk given at the XXXVII Brazilian Workshop on Nuclear Physics, September 2013
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1412.2077 [pdf]
J.Phys.Conf.Ser.(2015)·3 citations
09
[Submitted on 4 Dec 2014] (cross-list from gr-qc)
Stability of thin-shell interfaces inside compact stars
Jonas P. Pereira🇮🇹 · Jaziel G. Coelho🇮🇹 · Jorge A. Rueda🇮🇹
We use the thin-shell Darmois-Israel formalism to model and assess the stability of the interfaces separating phases, e.g. the core and the crust, within compact stars. We exemplify the relevance and non-triviality of this treatment in the simplest case of an incompressible star, in constant pressure phase transitions, and in the case of strange quark stars with crust.
Comments:
matches version published in Physical Review D
Subjects:
General Relativity and Quantum Cosmology (gr-qc); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1412.1848 [pdf]
PRD(2014)·21 citations
10
[Submitted on 5 Dec 2014] (cross-list from hep-ph)
Exact solutions of the (0+1)-dimensional kinetic equation in the relaxation time approximation
Ewa Maksymiuk🇵🇱
We present exact solutions of the (0+1)-dimensional kinetic equation for a massive gas in the relaxation time approximation. At first, we analyse the case of classical statistics and argue that the traditional second-order hydrodynamics misses the shear-bulk coupling. In the next step, we include Bose-Einstein and Fermi-Dirac statistics in the calculations and show that they are important for description of the effects connected with bulk viscosity.
Comments:
4 pages, 6 pictures, Talk presented at the Hot Quarks 2014, Las Negras, Spain. Slightly changed results for the bulk viscous pressure, conclusions unchanged
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1412.2063 [pdf]
J.Phys.Conf.Ser.(2015)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE