Nuclear Theory·nucl-th

Monday·July 27, 2015

10 papers—8 primary·2 cross-listed

01
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.
nucl-thPLB(2015)·39 citations
02
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.
nucl-thcond-mat.quant-gasphysics.chem-phPRC(2015)·156 citations
03
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.
nucl-thhep-phnucl-exNPA(2015)·23 citations
04
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.
nucl-thJ.Phys.Conf.Ser.(2013)·3 citations
05
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.
nucl-thPRC(2015)·14 citations
06
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.
nucl-thPRC(2016)·8 citations
07
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.
nucl-thPLB(2016)·67 citations
08
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.
nucl-thPRC(2015)·19 citations
09
Novel technique to extract experimental symmetry free energy information of nuclear matter
J. Mabiala · H. Zheng · A. Bonasera · P. Cammarata · K. Hagel · L. Heilborn · Z. Kohley · L. W. May · A. B. McIntosh · M. D. Youngs · A. Zarrella · S. J. Yennello
A new method of accessing information on the symmetry free energy from yields of fragments produced in Fermi-energy heavy-ion collisions is proposed. Furthermore, by means of quantum fluctuation analysis techniques, correlations between extracted symmetry free-energy coefficients with temperature and density were studied. The obtained results are consistent with those of commonly used isoscaling techniques.
↳ nucl-exnucl-thPRC(2015)·4 citations
10
Suppression of baryon diffusion and transport in a baryon rich strongly coupled quark-gluon plasma
Romulo Rougemont (Sao Paulo U.)🇧🇷 · Jorge Noronha (Sao Paulo U. & Columbia U.)🇧🇷 · Jacquelyn Noronha-Hostler (Columbia U.)🇺🇸
Five dimensional black hole solutions that describe the QCD crossover transition seen in $(2 + 1)$ -flavor lattice QCD calculations at zero and nonzero baryon densities are used to obtain predictions for the baryon susceptibility, baryon conductivity, baryon diffusion constant, and thermal conductivity of the strongly coupled quark-gluon plasma in the range of temperatures $130 MeV \leq T \leq 300 MeV$ and baryon chemical potentials $0 \leq μ_{B} \leq 400 MeV$ . Diffusive transport is predicted to be suppressed in this region of the QCD phase diagram, which is consistent with the existence of a critical end point at larger baryon densities. We also calculate the fourth-order baryon susceptibility at zero baryon chemical potential and find quantitative agreement with recent lattice results. The baryon transport coefficients computed in this paper can be readily implemented in state-of-the-art hydrodynamic codes used to investigate the dense QGP currently produced at RHIC's low energy beam scan.
↳ hep-phhep-thnucl-exnucl-thPRL(2015)·96 citations

Affiliations

first authorsco-authorsvia INSPIRE