Nuclear Theory·nucl-th
12 papers—7 primary·5 cross-listed
Castaly Fan · Praveen C. Srivastava · Larry Zamick
We perform shell model calculations for Cr using GXPF1A and FPD6 interactions by varying single particle energies. We find a scaling behavior which leads to the finding that many different sets of interactions with vastly different single particle energies can give almost identical results for the yrast spectrum of Cr
Jussi Auvinen🇷🇸 · Kari J. Eskola🇫🇮 · Pasi Huovinen🇷🇸 · Harri Niemi🇫🇮 · Risto Paatelainen🇨🇭 · Peter Petreczky🇺🇸
We investigate the temperature dependence of the shear viscosity to entropy density ratio using a piecewise linear parametrization. To determine the optimal values of the parameters and the associated uncertainties, we perform a global Bayesian model-to-data comparison on Au+Au collisions at GeV and Pb+Pb collisions at TeV and TeV, using a 2+1D hydrodynamical model with the EKRT initial state. We provide three new parametrizations of the equation of state (EoS) based on contemporary lattice results and hadron resonance gas, and use them and the widely used parametrization to explore the uncertainty in the analysis due to the choice of the equation of state. We found that is most constrained in the temperature range -- MeV, where, for all EoSs, when taking into account the 90% credible intervals. In this temperature range the EoS parametrization has only a small effect on the favored value, which is less than the uncertainty of the analysis using a single EoS parametrization. Our parametrization of leads to a slightly larger minimum value of than the previously used parametrizations. When we constrain our parametrization to mimic the previously used parametrizations, our favored value is reduced, and the difference becomes statistically insignificant.
Jaseer Ahmed🇨🇦 · P. G. Blunden🇨🇦 · W. Melnitchouk🇺🇸
We use a recently developed dispersive approach to compute the two-photon exchange (TPE) correction to elastic electron-proton scattering, including contributions from hadronic and resonant intermediate states below~1.8~GeV. For the transition amplitudes from the proton ground state to the resonant excited states we employ new exclusive meson electroproduction data from CLAS at ~GeV, and we explore the effects of both fixed and dynamic widths for the resonances. Among the resonant states, the becomes dominant for ~GeV, with a sign opposite to the comparably sized contribution, leading to an overall increase in the size of the TPE correction to the cross section relative to the nucleon only contribution at higher values. The results are in good overall agreement with recent to cross section ratio and polarization transfer measurements, and provide compelling evidence for a resolution of the electric to magnetic form factor ratio discrepancy.
We investigate the three-baryon system with charm +1 in a simple model. Charmed lambda is assumed to orbit an unperturbed deuteron in a charmed lambda-deuteron potential based on a separable charmed lambda-nucleon potential from chiral effective field theory techniques extrapolations of lattice QCD data for the and partial waves. We have estimated the strength and the range of the d potential. Also, the particle momentum distribution in is presented and compared by particle in . It is found that there is no bound state by solving eigenvalue condition equation.
Xu Meng · Shisheng Zhang · Lin Guo · Lisheng Geng · Ligang Cao
The effective isospin-density dependent pairing interaction (P1) [S. S. Zhang, U. Lombardo and E. G. Zhao, Sci. Chin. Phys. Mech. Astro. {\bf 54}, 236 (2011)] extracted from neutron pairing gaps for S in asymmetric nuclear matter calculations [S. S. Zhang, L. G. Cao, U. Lombardo, et al. Phys. Rev. C {\bf 81}, 044313 (2010)] is employed to study the bulk properties of Ca, Ni, Zr and Sn isotopes. The odd-even mass (OEM) staggering is calculated by the Skyrme Hartree-Fock plus BCS method (SHF + BCS) with the SkP interaction. For comparison, we study two other types of isovector effective pairing interactions. One is also extracted from pairing gaps of infinite nuclear matter by the Brueckner-Hartree-Fock (BHF) method but for free spectrum (P2). The other is obtained by fitting the empirical OEM (P3). An isoscalar effective pairing interaction (P4) is also adopted which is determined by fitting the empirical OEM. We find that interaction P1 can better describe the OEM staggering of Ni, Zr and Sn isotopes by compared with interaction P2, in terms of root mean square deviations to the empirical OEM, respectively. On the other hand, the performance of P1 and P2 is comparable for Ca isotopes. For Ca and Ni isotopes, P1 behaves similarly as P3, but for Zr isotopes P1 is better than P3 by . Among the four pairing interactions studied, P4 performs the worst. Therefore, one may conclude that for neutron pairings in finite nuclei, the isovector pairings are preferred than the isoscalar one. It is quite interesting to note that the pairing interaction P1 extracted from nuclear matter calculations can describe pairing gaps of finite nuclei as well as or even better than the interaction P3 directly fitted to finite nuclei.
Vincent Gaebel🇩🇪 · Michel Bonne🇩🇪 · Tom Reichert🇩🇪 · Ajdin Burnic🇧🇦 · Paula Hillmann🇩🇪 · Marcus Bleicher🇩🇪
The deuteron coalescence parameter in proton+proton and nucleus+nucleus collisions in the energy range of 900 - 7000 GeV for proton+proton and 2 - 2760 GeV for nucleus+nucleus collisions is analyzed with the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport model, supplemented by an event-by-event phase space coalescence model for deuteron and anti-deuteron production. The results are compared to data by the E866, E877, PHENIX, STAR and ALICE experiments. The values are calculated from the final spectra of protons and deuterons. At lower energies, GeV, drops drastically with increasing energy. The calculations confirm that this is due to the increasing freeze-out volume reflected in . At higher energies, GeV, saturates at a constant level. This qualitative change and the vanishing of the volume suppression is shown to be due to the development of strong radial flow with increasing energy. The flow leads to strong space-momentum correlations which counteract the volume effect.
Two-particle correlations based on the multiplicity of selected isobars are found to be sensitive to the parameterization of the fragments' binding energies and the breakup volume assumed in the model calculations. The properties of these correlations have been examined in the framework of the Statistical Multifragmentation Model as a function of the breakup temperature. The model calculations suggest that the maxima of these correlation functions occur at well separated temperatures as the breakup volumes used in the model vary from 3 to 6 times that at normal density. These volumes are within the range assumed in most statistical calculations and supported by experiments. Besides their position, the height and width of the maxima are also found to be sensitive to the parameterization of the fragments' binding energy. The magnitude of all these effects also depends on the isobars considered in the correlations. We found that, due to an interplay between the symmetry energy and the volume dependent terms of the Helmholtz free energy, in the case of nearly symmetric sources, correlations involving light mirror nuclei seem to enhance these effects. We suggest that the proposed correlation functions could be used to extract information on the fragments' energies and on the breakup volume of nuclear sources.
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