Nuclear Theory·nucl-th

Friday·February 13, 2015

13 papers—5 primary·8 cross-listed

01
[Submitted on 11 Feb 2015]
Ab-initio calculation of the photonuclear cross section of $^{10}$ B
M.K.G. Kruse🇺🇸 · W.E. Ormand🇺🇸 · C.W. Johnson🇺🇸
We present for the first-time the photonuclear cross section of $^{10}$ B calculated within the ab-initio No Core Shell Model framework. Realistic two-nucleon (NN) chiral forces up to next-to-next-to-next-order (N3LO), which have been softened by the similarity renormalization group method (SRG) to $λ = 2.02$ fm $^{- 1}$ , were utilized. The electric-dipole response function is calculated using the Lanczos method. The effects of the continuum were accounted for by including neutron escape widths derived from R-matrix theory. The calculated cross section agrees well with experimental data in terms of structure as well as in absolute peak height, $σ_{max} = 4.85 mb$ at photon energy $ω = 23.61 MeV$ , and integrated cross section $85.36 MeV \cdot mb$ . We test the Brink hypothesis by calculating the electric-dipole response for the first five positive-parity states in $^{10}$ B and verify that dipole excitations built upon the ground- and excited states have similar characteristics.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1502.03464 [pdf]
1 citation
02
[Submitted on 12 Feb 2015]
Ab initio-driven nuclear energy density functional method. A proposal for safe/correlated/improvable parametrizations of the off-diagonal EDF kernels
T. Duguet · M. Bender · J.-P. Ebran · T. Lesinski · V. Somà
This programmatic paper lays down the possibility to reconcile the necessity to resum many-body correlations into the energy kernel with the fact that safe multi-reference energy density functional (EDF) calculations cannot be achieved whenever the Pauli principle is not strictly enforced, as is for example the case when many-body correlations are parametrized under the form of empirical density dependencies. Our proposal is to exploit a newly developed ab initio many-body formalism to guide the construction of safe, explicitly correlated and systematically improvable parametrizations of the {\it off-diagonal} energy and norm kernels that lie at the heart of the nuclear EDF method. The many-body formalism of interest relies on the concepts of symmetry breaking {\it and} restoration that have made the fortune of the nuclear EDF method and is, as such, amenable to this guidance. After elaborating on our proposal, we briefly outline the project we plan to execute in the years to come.
Comments:
14 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.03672 [pdf]
EPJA(2015)·16 citations
03
[Submitted on 12 Feb 2015]
Fitting Single Particle Energies in $s d g h$ Major Shell
E. Dikmen · O. Öztürk · Y. Cengiz
We have performed two kinds of non-linear fitting procedures to the single-particle energies in the $s d g h$ major shell to obtain better shell model results. The low-lying energy eigenvalues of the light Sn isotopes with $A = 103 - 110$ in the $s d g h$ -shell are calculated in the framework of the nuclear shell model by using CD-Bonn two-body effective nucleon-nucleon interaction. The obtained energy eigenvalues are fitted to the corresponding experimental values by using two different non-linear fitting procedures, i.e., downhill simplex method and clonal selection method. The unknown single-particle energies of the states $2 s_{1/2}$ , $1 d_{3/2}$ , and $0 h_{11/2}$ are used in the fitting methods to obtain better spectra of the $^{104, 106, 108, 110}$ Sn isotopes. We compare the energy spectra of the $^{104, 106, 108, 110}$ Sn and $^{103, 105, 107, 109}$ Sn isotopes with/without a nonlinear fit to the experimental results.
Comments:
8 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.03677 [pdf]
Commun.Theor.Phys.(2015)·2 citations
04
[Submitted on 12 Feb 2015]
Charge splitting of directed flow and charge-dependent effects in pion spectra in heavy ion collisions
A. Rybicki🇵🇱 · A. Szczurek🇵🇱 · M. Klusek-Gawenda🇵🇱 · M. Kielbowicz🇵🇱
The large and rapidly varying electric and magnetic fields induced by the spectator systems moving at ultrarelativistic velocities induce a charge splitting of directed flow, $v_{1}$ , of positive and negative pions in the final state of the heavy ion collision. The same effect results in a very sizeable distortion of charged pion spectra as well as ratios of charged pions ( $π^{+} / π^{-}$ ) emitted at high values of rapidity. Both phenomena are sensitive to the actual distance between the pion emission site and the spectator system. This distance $d_{E}$ appears to decrease with increasing rapidity of the pion, and comes below $\sim$ 1~fm for pions emitted close to beam rapidity. In this paper we discuss how these findings can shed new light on the space-time evolution of pion production as a function of rapidity, and on the longitudinal evolution of the system created in heavy ion collisions.
Comments:
8 pages, 3 figures a talk by A. Rybicki at the X Workshop on Particle Correlations and Femtoscopy (WPCF 2014), Gyöngyös, Hungary, 2014
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1502.03689 [pdf]
3 citations
05
[Submitted on 12 Feb 2015]
Toward a solution to the $R_{AA}$ and $v_{2}$ puzzle for heavy quarks
Santosh K. Das🇮🇹 · Francesco Scardina🇮🇹 · Salvatore Plumari🇮🇹 · Vincenzo Greco🇮🇹
The heavy quarks constitutes a unique probe of the quark-gluon plasma properties. Both at RHIC and LHC energies a puzzling relation between the nuclear modification factor $R_{AA} (p_{T})$ and the elliptic flow $v_{2} (p_{T})$ has been observed which challenged all the existing models, especially for D mesons. We discuss how the temperature dependence of the heavy quark drag coefficient is responsible for a large part of such a puzzle. In particular, we have considered four different models to evaluate the temperature dependence of drag and diffusion coefficients propagating through a quark gluon plasma (QGP). All the four different models are set to reproduce the same $R_{AA} (p_{T})$ observed in experiments at RHIC and LHC energy. We point out that for the same $R_{AA} (p_{T})$ one can generate 2-3 times more $v_{2}$ depending on the temperature dependence of the heavy quark drag coefficient. A non-decreasing drag coefficient as $T \to T_{c}$ is a major ingredient for a simultaneous description of $R_{AA} (p_{T})$ and $v_{2} (p_{T})$ .
Comments:
7 pages, 6 figures, Accepted for publication in Physics Letters B
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1502.03757 [pdf]
PLB(2015)·227 citations

Affiliations

first authorsco-authorsvia INSPIRE

Ab-initio calculation of the photonuclear cross section of 10B

Ab initio-driven nuclear energy density functional method. A proposal for safe/correlated/improvable parametrizations of the off-diagonal EDF kernels

Fitting Single Particle Energies in sdgh Major Shell

Charge splitting of directed flow and charge-dependent effects in pion spectra in heavy ion collisions

Toward a solution to the RAA​ and v2​ puzzle for heavy quarks

Affiliations

Ab-initio calculation of the photonuclear cross section of $^{10}$ B

Fitting Single Particle Energies in $s d g h$ Major Shell

Toward a solution to the $R_{AA}$ and $v_{2}$ puzzle for heavy quarks