Nuclear Theory·nucl-th

Monday·December 26, 2016

6 papers—5 primary·1 cross-listed

01
[Submitted on 23 Dec 2016]
Boltzmann-Langevin Approach to Pre-equilibrium Correlations in Nuclear Collisions
Sean Gavin🇺🇸 · George Moschelli🇺🇸 · Christopher Zin🇺🇸
Correlations born before the onset of hydrodynamic flow can leave observable traces on the final state particles. Measurement of these correlations can yield important information on the isotropization and thermalization process. Starting from a Boltzmann-like kinetic theory in the presence of dynamic Langevin noise, we derive a new partial differential equation for the two-particle correlation function that respects the microscopic conservation laws. We illustrate how this equation can be used to study the effect of thermalization on long range correlations.
Comments:
11 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1612.07856 [pdf]
PRC(2017)·19 citations
02
[Submitted on 23 Dec 2016]
On the chiral covariant approach to $ρρ$ scattering
Li-Sheng Geng🇨🇳 · Raquel Molina🇺🇸 · Eulogio Oset🇪🇸
We examine in detail a recent work (D.~Gülmez, U.-G.~Meißner and J.~A.~Oller, Eur. Phys. J. C 77:460 (2017)), where improvements to make $ρρ$ scattering relativistically covariant are made. The paper has the remarkable conclusion that the $J = 2$ state disappears with a potential which is much more attractive than for $J = 0$ , where a bound state is found. We trace this abnormal conclusion to the fact that an "on-shell" factorization of the potential is done in a region where this potential is singular and develops a large discontinuous and unphysical imaginary part. A method is developed, evaluating the loops with full $ρ$ propagators, and we show that they do not develop singularities and do not have an imaginary part below threshold. With this result for the loops we define an effective potential, which when used with the Bethe-Salpeter equation provides a state with $J = 2$ around the energy of the $f_{2} (1270)$ . In addition, the coupling of the state to $ρρ$ is evaluated and we find that this coupling and the $T$ matrix around the energy of the bound state are remarkably similar to those obtained with a drastic approximation used previously, in which the $q^{2}$ terms of the propagators of the exchanged $ρ$ mesons are dropped, once the cut-off in the $ρρ$ loop function is tuned to reproduce the bound state at the same energy.
Comments:
11 pages, 11 figures, version appeared in Chinese Physics C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.07871 [pdf]
CPC(2017)·28 citations
03
[Submitted on 23 Dec 2016]
Effective forces between quantum bound states
Alexander Rokash🇩🇪 · Evgeny Epelbaum🇺🇸 · Hermann Krebs🇺🇸 · Dean Lee🇺🇸
Recent ab initio lattice studies have found that the interactions between alpha particles (4He nuclei) are sensitive to seemingly minor details of the nucleon-nucleon force such as interaction locality. In order to uncover the essential physics of this puzzling phenomenon without unnecessary complications, we study a simple model involving two-component fermions in one spatial dimension. We probe the interaction between two bound dimers for several different particle-particle interactions and measure an effective potential between the dimers using external point potentials which act as numerical tweezers. We find that the strength and range of the local part of the particle-particle interactions play a dominant role in shaping the interactions between the dimers and can even determine the overall sign of the effective potential.
Comments:
Final version to be published in Physical Review Letters. Main text: 5 pages, 5 figures. Supplemental material: 2 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Lattice (hep-lat); Quantum Physics (quant-ph)
arXiv:
1612.08004 [pdf]
PRL(2017)·10 citations
04
[Submitted on 23 Dec 2016]
Uncertainties in constraining low-energy constants from $^{3}$ H $β$ decay
P. Klos🇩🇪 · A. Carbone🇩🇪 · K. Hebeler🇩🇪 · J. Menéndez🇯🇵 · A. Schwenk🇩🇪
We discuss the uncertainties in constraining low-energy constants of chiral effective field theory from $^{3}$ H $β$ decay. The half-life is very precisely known, so that the Gamow-Teller matrix element has been used to fit the coupling $c_{D}$ of the axial-vector current to a short-range two-nucleon pair. Because the same coupling also describes the leading one-pion-exchange three-nucleon force, this in principle provides a very constraining fit, uncorrelated with the $^{3}$ H binding energy fit used to constrain another low-energy coupling in three-nucleon forces. However, so far such $^{3}$ H half-life fits have only been performed at a fixed cutoff value. We show that the cutoff dependence due to the regulators in the axial-vector two-body current can significantly affect the Gamow-Teller matrix elements and consequently also the extracted values for the $c_{D}$ coupling constant. The degree of the cutoff dependence is correlated with the softness of the employed NN interaction. As a result, present three-nucleon forces based on a fit to $^{3}$ H $β$ decay underestimate the uncertainty in $c_{D}$ . We explore a range of $c_{D}$ values that is compatible within cutoff variation with the experimental $^{3}$ H half-life and estimate the resulting uncertainties for many-body systems by performing calculations of symmetric nuclear matter.
Comments:
9 pages, 11 figures, published version, includes Erratum, which corrects Figs. 2-6 due to the incorrect c_D relation between 3N forces and two-body currents used
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.08010 [pdf]
EPJA(2017)·26 citations
05
[Submitted on 23 Dec 2016]
Heavy-flavor production and medium properties in high-energy nuclear collisions - What next?
G. Aarts🇬🇧 · J. Aichelin🇫🇷 · C. Allton🇬🇧 · R. Arnaldi🇮🇹 · S. A. Bass🇺🇸 · C. Bedda🇳🇱 · N. Brambilla🇩🇪 · E. Bratkovskaya🇩🇪 · P. Braun-Munzinger🇩🇪 · G. E. Bruno🇮🇹 · T. Dahms🇩🇪 · S. K. Das🇮🇹 and 37 other authors
Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop "Tomography of the quark-gluon plasma with heavy quarks}, which was held in October 2016 in Leiden, the Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.
Comments:
18 pages, 4 figures, Lorentz workshop document, submitted to EPJ A
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1612.08032 [pdf]
EPJA(2017)·122 citations
06
[Submitted on 21 Dec 2016] (cross-list from physics.atom-ph)
Nuclear size corrections to the energy levels of single-electron atoms
Babak Nadiri Niri
A study is made of nuclear size corrections to the energy levels of single-electron atoms for the ground state of hydrogen like atoms. We consider Fermi charge distribution to the nucleus and calculate atomic energy level shift due to the finite size of the nucleus in the perturbation theory context. The exact relativistic correction based upon the available analytical calculations is compared to the result of first-order relativistic perturbation theory and the non-relativistic approximation. We find small discrepancies between our perturbative results and those obtained from exact relativistic calculation even for large nuclear charge number .
Comments:
This manuscript includes 12 pages, 2 figures and 2 tables
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th)
arXiv:
1612.08042 [pdf]
NPB-D-2016-00707·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Boltzmann-Langevin Approach to Pre-equilibrium Correlations in Nuclear Collisions

On the chiral covariant approach to ρρ scattering

Effective forces between quantum bound states

Uncertainties in constraining low-energy constants from 3H β decay

Heavy-flavor production and medium properties in high-energy nuclear collisions - What next?

Nuclear size corrections to the energy levels of single-electron atoms

Affiliations

On the chiral covariant approach to $ρρ$ scattering

Uncertainties in constraining low-energy constants from $^{3}$ H $β$ decay