Nuclear Theory·nucl-th

Tuesday·February 17, 2015

12 papers—7 primary·5 cross-listed

01
[Submitted on 15 Feb 2015]
The Role of Density Dependent One-Body Momentum Distribution on the Calculation of Ground State Properties of Closed Shell Nuclei
Hodjat Mariji
The nucleon single-particle energies (SPEs) of the selected closed shell nuclei; that is, 16O, 40Ca, and 56Ni, are obtained by using the diagonal matrix elements of two-body effective interaction, which generated through the lowest order constrained variational (LOCV) calculations for the symmetric nuclear matter with the AV18 phenomenological nucleon-nucleon potential. The SPEs at the major levels of nuclei are calculated by employing a Hartree-Fock inspired-scheme in the spherical harmonic oscillator basis. In the scheme, the correlation influences are taken into account by imposing the nucleon effective mass factor on the radial wave functions of the major levels. Replacing the density-dependent one-body momentum distribution functions of nucleons, n(k,rho), with the Heaviside functions, the role of n(k,rho) on the nucleon SPEs at the major levels of the selected closed shell nuclei, is investigated. The best fit of spin-orbit splitting is taken into account when correcting the major levels of the nuclei by using the parameterized Wood-Saxon potential and the AV18 density-dependent mean field potential which is constructed by the LOCV method. Considering the point-like protons in the spherical Coulomb's potential well, the single-proton energies are corrected. The results show the importance of including n(k,rho), instead of the Heaviside functions, in the calculation of nucleon SPEs at the different levels, particularly the valence levels, of the closed shell nuclei.
Comments:
This work has been superseded by arXiv:1606.07964
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.04347 [pdf]
0 citations
02
[Submitted on 16 Feb 2015]
Effective theory for the non-rigid rotor in an electromagnetic field: Toward accurate and precise calculations of E2 transitions in deformed nuclei
E. A. Coello Pérez · T. Papenbrock
We present a model-independent approach to electric quadrupole transitions of deformed nuclei. Based on an effective theory for axially symmetric systems, the leading interactions with electromagnetic fields enter as minimal couplings to gauge potentials, while subleading corrections employ gauge-invariant non-minimal couplings. This approach yields transition operators that are consistent with the Hamiltonian, and the power counting of the effective theory provides us with theoretical uncertainty estimates. We successfully test the effective theory in homonuclear molecules that exhibit a large separation of scales. For ground-state band transitions of rotational nuclei, the effective theory describes data well within theoretical uncertainties at leading order. In order to probe the theory at subleading order, data with higher precision would be valuable. For transitional nuclei, next-to-leading order calculations and the high-precision data are consistent within the theoretical uncertainty estimates. We also study the faint inter-band transitions within the effective theory and focus on the $E 2$ transitions from the $0_{2}^{+}$ band (the " $β$ band") to the ground-state band. Here, the predictions from the effective theory are consistent with data for several nuclei, thereby proposing a solution to a long-standing challenge.
Comments:
21 pages. Improved uncertainty estimates
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1502.04405 [pdf]
PRC(2015)·24 citations
03
[Submitted on 16 Feb 2015]
Multi-dimensional fission model with a complex absorbing potential
Guillaume Scamps · Kouichi Hagino
We study the dynamics of multi-dimensional quantum tunneling by introducing a complex absorbing potential to a two-dimensional model for spontaneous fission. We fist diagonalize the Hamiltonian with the complex potential to determine a resonance state as well as its life-time. We then solve the time-dependent Schrödinger equation with such basis in order to investigate the tunneling path. We compare this method with the semi-classical method for multi-dimensional tunneling with imaginary time. A good agreement is found both for the life-time and for the tunneling path.
Comments:
7 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.04418 [pdf]
PRC(2015)·16 citations
04
[Submitted on 16 Feb 2015]
Quarks Production in the Quark-Gluon Plasma Created in Relativistic Heavy Ion Collisions
Marco Ruggieri🇮🇹 · Salvatore Plumari🇮🇹 · Francesco Scardina🇮🇹 · Vincenzo Greco🇮🇹
In this article we report on our results about quark production and chemical equilibration of quark-gluon plasma. Our initial condition corresponds to a classic Yang-Mills spectrum, in which only gluon degrees of freedom are considered; the initial condition is then evolved to a quark-gluon plasma by means of relativistic transport theory with inelastic processes which permit the conversion of gluons to $q q ˉ$ pairs. We then compare our results to the ones obtained with a standard Glauber model initialization. We find that regardless of the initial condition the final stage of the system contains an abundant percentage of $q q ˉ$ pairs; moreover spanning the possible coupling from weak to strong we find that unless the coupling is unrealistically small, both production rate and final percentage of fermions is quite large.
Comments:
Minor changes. Published on Nuclear Physics A
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1502.04596 [pdf]
NPA(2015)·17 citations
05
[Submitted on 16 Feb 2015]
Shape and flow fluctuations in ultra-central Pb+Pb collisions at the LHC
Chun Shen🇺🇸 · Zhi Qiu🇺🇸 · Ulrich Heinz🇺🇸
In ultra-central heavy-ion collisions, anisotropic hydrodynamic flow is generated by density fluctuations in the initial state rather than by geometric overlap effects. For a given centrality class, the initial fluctuation spectrum is sensitive to the method chosen for binning the events into centrality classes. We show that sorting events by total initial entropy or by total final multiplicity yields event classes with equivalent statistical fluctuation properties, in spite of viscous entropy production during the fireball evolution. With this initial entropy-based centrality definition we generate several classes of ultra-central Pb+Pb collisions at LHC energies and evolve the events using viscous hydrodynamics with non-zero shear but vanishing bulk viscosity. Comparing the predicted anisotropic flow coefficients for charged hadrons with CMS data we find that both the Monte Carlo Glauber (MC-Glb) and Monte Carlo Kharzeev-Levin-Nardi (MC-KLN) models produce initial fluctuation spectra that are incompatible with the measured final anisotropic flow power spectrum, for any choice of the specific shear viscosity. In spite of this failure, we show that the hydrodynamic model can qualitatively explain, in terms of event-by-event fluctuations of the anisotropic flow coefficients and flow angles, the breaking of flow factorization for elliptic, triangular and quadrangular flow measured by the CMS experiment. For elliptic flow, this factorization breaking is large in ultra-central collisions. We conclude that the bulk of the experimentally observed flow factorization breaking effects are qualitatively explained by hydrodynamic evolution of initial-state fluctuations, but that their quantitative description requires a better understanding of the initial fluctuation spectrum.
Comments:
11 pages, 11 figures; In v2 and the current version, we updated all the calculations (except for Fig. 2) that do not include microscopic NN-correlations with a hard core radius of 0.9 fm. In v1, some of the results are done with a smaller hard core radius of 0.4 fm. We also reduced the statistical errors in Figs. 5-8 by increasing the simulated events to 1000 for every set of the run
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1502.04636 [pdf]
PRC(2015)·58 citations
06
[Submitted on 16 Feb 2015]
Polarized deuteron charge-exchange reaction $d p - > pp_{s} N π$ in the Delta-isobar region
Yu.N. Uzikov (JINR, Dubna)🇷🇺 · J. Haidenbauer (IAS, Juelich)🇩🇪 · C. Wilkin (UCL, London)🇬🇧
Mechanisms of the charge exchange reaction $d p \to {pp}_{s} N π$ , where ${pp}_{s}$ is a two-proton system at low excitation energy, are studied at beam energies 1 -- 2 GeV and for invariant masses $M_{X}$ of the final $N π$ system that correspond to the formation of the $Δ (1232)$ isobar. The direct mechanism, where the initial proton is excited into the $Δ (1232)$ , dominates and explains the existing data on the unpolarized differential cross section and spherical tensor analyzing power $T_{22}$ for $M_{X} > 1.2$ GeV/ $c^{2}$ . However, this model fails to describe $T_{20}.
Comments:
6 pages, 3 figures; talk given at Baldin ISHEPP XXII
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.04675 [pdf]
PoS(2015)·5 citations
07
[Submitted on 16 Feb 2015]
Accurate nuclear radii and binding energies from a chiral interaction
A. Ekström · G. R. Jansen · K. A. Wendt · G. Hagen · T. Papenbrock · B. D. Carlsson · C. Forssén · M. Hjorth-Jensen · P. Navrátil · W. Nazarewicz
With the goal of developing predictive ab-initio capability for light and medium-mass nuclei, two-nucleon and three-nucleon forces from chiral effective field theory are optimized simultaneously to low-energy nucleon-nucleon scattering data, as well as binding energies and radii of few-nucleon systems and selected isotopes of carbon and oxygen. Coupled-cluster calculations based on this interaction, named NNLO $_{sat}$ , yield accurate binding energies and radii of nuclei up to $^{40}$ Ca, and are consistent with the empirical saturation point of symmetric nuclear matter. In addition, the low-lying collective $J^{π} = 3^{-}$ states in $^{16}$ O and $^{40}$ Ca are described accurately, while spectra for selected $p$ - and $s d$ -shell nuclei are in reasonable agreement with experiment.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1502.04682 [pdf]
PRC(2015)·541 citations

Affiliations

first authorsco-authorsvia INSPIRE

The Role of Density Dependent One-Body Momentum Distribution on the Calculation of Ground State Properties of Closed Shell Nuclei

Effective theory for the non-rigid rotor in an electromagnetic field: Toward accurate and precise calculations of E2 transitions in deformed nuclei

Multi-dimensional fission model with a complex absorbing potential

Quarks Production in the Quark-Gluon Plasma Created in Relativistic Heavy Ion Collisions

Shape and flow fluctuations in ultra-central Pb+Pb collisions at the LHC

Polarized deuteron charge-exchange reaction dp−>pps​Nπ in the Delta-isobar region

Accurate nuclear radii and binding energies from a chiral interaction

Affiliations

Polarized deuteron charge-exchange reaction $d p - > pp_{s} N π$ in the Delta-isobar region