Nuclear Theory·nucl-th

Monday·July 27, 2015

10 papers—8 primary·2 cross-listed

01
[Submitted on 24 Jul 2015]
Covariance Analysis of Symmetry Energy Observables from Heavy Ion Collision
Yingxun Zhang🇨🇳 · M. B. Tsang🇺🇸 · Zhuxia Li🇨🇳
Using covariance analysis, we quantify the correlations between the interaction parameters in a transport model and the observables commonly used to extract information of the Equation of State of Asymmetric Nuclear Matter in experiments. By simulating $^{124}$ Sn+ $^{124}$ Sn, $^{124}$ Sn+ $^{112}$ Sn and $^{112}$ Sn+ $^{112}$ Sn reactions at beam energies of 50 and 120 MeV per nucleon, we have identified that the nucleon effective mass splitting are most strongly correlated to the neutrons and protons yield ratios with high kinetic energy from central collisions especially at high incident energy. The best observable to determine the slope of the symmetry energy, L, at saturation density is the isospin diffusion observable even though the correlation is not very strong ( $\sim$ 0.7). Similar magnitude of correlation but opposite in sign exists for isospin diffusion and nucleon isoscalar effective mass. At 120 MeV/u, the effective mass splitting and the isoscalar effective mass also have opposite correlation for the double n/p and isoscaling p/p yield ratios. By combining data and simulations at different beam energies, it should be possible to place constraints on the slope of symmetry energy (L) and effective mass splitting with reasonable uncertainties.
Comments:
13 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.06718 [pdf]
PLB(2015)·39 citations
02
[Submitted on 24 Jul 2015]
The Magnus expansion and the in-medium similarity renormalization group
T.D. Morris · N. Parzuchowski · S.K. Bogner
We present an improved variant of the in-medium similarity renormalization group (IM-SRG) based on the Magnus expansion. In the new formulation, one solves flow equations for the anti-hermitian operator that, upon exponentiation, yields the unitary transformation of the IM-SRG. The resulting flow equations can be solved using a first-order Euler method without any loss of accuracy, resulting in substantial memory savings and modest computational speedups. Since one obtains the unitary transformation directly, the transformation of additional operators beyond the Hamiltonian can be accomplished with little additional cost, in sharp contrast to the standard formulation of the IM-SRG. Ground state calculations of the homogeneous electron gas (HEG) and $^{16}$ O nucleus are used as test beds to illustrate the efficacy of the Magnus expansion.
Comments:
12 pages, 9 figures; fixed typos and added a reference
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); physics.chem-ph (physics.chem-ph)
arXiv:
1507.06725 [pdf]
PRC(2015)·156 citations
03
[Submitted on 24 Jul 2015]
Constraining heavy quark energy loss using $B$ and $D$ meson measurements in heavy ion collision at RHIC and LHC energies
Kapil Saraswat🇮🇳 · Prashant Shukla🇮🇳 · Venktesh Singh🇮🇳
In this work, we calculate energy loss of heavy quark (charm and bottom) due to elastic collisions and gluon radiation in hot/dense medium. The collisional energy loss has been obtained using QCD calculations. The radiative energy loss is calculated using reaction operator formalism and generalized dead cone approach. We rederive the energy loss expression using same assumptions as generalized dead cone approach but obtain slightly different results. We also improve the model employed to calculate path length and the system evolution. The nuclear modification factors $R_{AA}$ including shadowing and energy loss are evaluated for $B$ and $D$ mesons and are compared with the measurements in PbPb collision at $s_{N N}$ = 2.76 TeV and with the D meson and Heavy flavour (HF) electrons measurements in AuAu collision at $s_{N N}$ = 200 GeV. The radiative energy loss calculated by reaction operator formalism added with collisional energy loss describes the RHIC HF electron suppression in high $p_{T}$ range. It also describes the LHC measurement of $B$ meson suppression but overestimates the suppression of $D$ meson. The radiative energy loss from generalized dead cone approach describes the charm suppression at both RHIC as well as LHC energies and requires energy loss due to collisions to be added in order to describe the bottom suppression at LHC.
Comments:
27 pages, 16 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1507.06742 [pdf]
NPA(2015)·23 citations
04
[Submitted on 24 Jul 2015]
Configuration mixing effects in neutron-rich carbon isotopes
C. X. Yuan · F. R. Xu · C. Qi
Shell model calculations are done to study the structure of neutron-rich carbon isotopes. For both even-A and odd-A neutron-rich carbon isotopes, the energy levels are strongly affected by the configuration mixing of valence neutrons. The calculated energy levels in the nucleus $^{17}$ C are significantly improved compared with experimental values when the model space of the three valence neutrons is enlarged from pure $ν (0 d_{5/2})^{3}$ configuration to full $s d$ space. We also investigate the configuration mixing effect on the $B (E 2)$ values in even-even nuclei $^{16 - 20}$ C.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.06809 [pdf]
J.Phys.Conf.Ser.(2013)·3 citations
05
[Submitted on 24 Jul 2015]
Neutrino absorption by hot nuclei in supernova environments
Alan A. Dzhioev🇷🇺 · A. I. Vdovin🇷🇺 · J. Wambach🇩🇪
Using the thermal quasiparticle random phase approximation, we study the process of neutrino and antineutrino capture on hot nuclei in supernova environments. For the sample nuclei $^{56}$ Fe and $^{82}$ Ge we perform a detailed analysis of thermal effects on the strength distribution of allowed Gamow-Teller transitions which dominate low-energy charged-current neutrino reactions. The finite temperature cross sections are calculated taking into account the contributions of both allowed and forbidden transitions. The enhancement of the low-energy cross sections is explained by considering thermal effects on the GT $_{\pm}$ strength. For $^{56}$ Fe we compare the calculated finite-temperature cross sections with those obtained from large-scale shell-model calculations.
Comments:
Minor revisions according to referee's recomendations
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.06872 [pdf]
PRC(2015)·14 citations
06
[Submitted on 24 Jul 2015]
Evidence for L-dependence generated by channel coupling: O16 scattering from C12 at 115.9 Mev
Raymond S. Mackintosh
The inclusion of strong coupling to states of projectile and target nuclei for 115.9 MeV \nuc{16}{O} scattering from \nuc{12}{C} leads to an S-matrix which, when subject to $S_{L} \to V (r)$ inversion, yields highly undulatory local potentials. Previous work has shown that explicitly $L$ -dependent non-undulatory potentials are equivalent to undulatory $L$ -independent potentials with the same S-matrix. Here we show that $L$ -independent equivalents for certain simple model $L$ -dependent potentials exhibit undulatory features qualitatively similar to those arising from channel coupling for 115.9 MeV \nuc{16}{O} scattering from \nuc{12}{C}. We discuss the relevance to the question of $L$ -dependence as a generic property of nucleus-nucleus interactions.
Comments:
8 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.06899 [pdf]
PRC(2016)·8 citations
07
[Submitted on 24 Jul 2015]
Magicity of neutron-rich isotopes within relativistic self-consistent approaches
Jia Jie Li🇨🇳 · Jérôme Margueron🇫🇷 · Wen Hui Long🇨🇳 · Nguyen Van Giai🇫🇷
The formation of new shell gaps in intermediate mass neutron-rich nuclei is investigated within the relativistic Hartree-Fock-Bogoliubov theory, and the role of the Lorentz pseudo-vector and tensor interactions is analyzed. Based on the Foldy-Wouthuysen transformation, we discuss in detail the role played by the different terms of the Lorentz pseudo-vector and tensor interactions in the appearing of the $N = 16$ , 32 and 34 shell gaps. The nuclei $^{24}$ O, $^{48}$ Si and $^{52, 54}$ Ca are predicted with a large shell gap and zero ( $^{24}$ O, $^{52}$ Ca) or almost zero ( $^{48}$ Si, $^{54}$ Ca) pairing gap, making them candidates for new magic numbers in exotic nuclei. We find from our analysis that the Lorentz pseudo-vector and tensor interactions induce very specific evolutions of single-particle energies, which could clearly sign their presence and reveal the need for relativistic approaches with exchange interactions.
Comments:
7 pages, 5 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.06918 [pdf]
PLB(2016)·67 citations
08
[Submitted on 22 Jul 2015]
Algebraic Solutions for $U^{B F} (5) - O^{B F} (6)$ Quantum Phase Transition in Odd Mass Number Nuclei
M. A. Jafarizadeh · M.Ghapanvari · N. Fouladi
The spherical to deformed $γ - u n s t ab l e$ shape- phase transition in odd-A nuclei is investigated by using the Dual algebraic structures and the affine $S U (1, 1)$ Lie Algebra within the framework of the interacting boson - fermion model. The new algebraic solution for A-odd nuclei is introduced. In this model, Single $j = 1/2$ and $3/2$ fermions are coupled with an even-even boson core. Energy spectra, quadruple electromagnetic transitions and an expectation value of the d-boson number operator are presented. Experimental evidence for the $U^{B F} (5) - O^{B F} (6)$ transition in odd -A $B a$ and $R h$ isotopes is presented. The low-states energy spectra and $B (E 2)$ values for these nuclei have been also calculated and compared with the experimental data.
Comments:
20 pages, 24 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1507.06933 [pdf]
PRC(2015)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE