Nuclear Theory·nucl-th

Monday·April 20, 2015

16 papers—6 primary·10 cross-listed

07
The recoil correction and spin-orbit force for the possible $B^{*} B ˉ^{*}$ and $D^{*} D ˉ^{*}$ states
Lu Zhao🇨🇳 · Li Ma🇨🇳 · Shi-Lin Zhu🇨🇳
In the framework of the one-boson exchange model, we have calculated the effective potentials between two heavy mesons $B^{*} B ˉ^{*}$ and $D^{*} D ˉ^{*}$ from the t- and u-channel $π$ -, $η$ -, $ρ$ -, $ω$ - and $σ$ -meson exchanges. We keep the recoil corrections to the $B^{*} B ˉ^{*}$ and $D^{*} D ˉ^{*}$ systems up to $O (\frac{1}{M ^{2}})$ , which turns out to be important for the very loosely bound molecular states. Our numerical results show that the momentum-related corrections are favorable to the formation of the molecular states in the $I^{G} = 1^{+}$ , $J^{P C} = 1^{+-}$ in the $B^{*} B ˉ^{*}$ and $D^{*} D ˉ^{*}$ systems.
↳ hep-phhep-exhep-latnucl-thNPA(2015)·17 citations
08
Magnetized plasminos in cold and hot QED plasmas
N. Sadooghi🇮🇷 · F. Taghinavaz🇮🇷
The complete quasi-particle spectrum of a magnetized electromagnetic plasma is systematically explored at zero and nonzero temperatures. To this purpose, the general structure of the one-loop corrected propagator of magnetized fermions is determined, and the dispersion relations arising from the pole of this propagator are numerically solved. It turns out that in the lowest Landau level, where only one spin direction is allowed, the spectrum consists of one positively (negatively) charged fermionic mode with positive (negative) spin. In contrast, in higher Landau levels, as an indirect consequence of the double spin degeneracy of fermions, the spectrum consists of two massless collective modes with left- and right-chiralities. The mechanism through which these new collective excitations are created in a uniform magnetic field is similar to the production mechanism of dynamical holes (plasminos) at finite temperature and zero magnetic fields. Whereas cold magnetized plasminos appear for moderate magnetic fields and for all positive momenta of propagating fermions, hot magnetized plasminos appear only in the limit of weak magnetic fields and soft momenta.
↳ hep-phhep-thnucl-thPRD(2015)·17 citations
09
Impact of weak interactions of free nucleons on the r-process in dynamical ejecta from neutron-star mergers
Stephane Goriely (1)🇧🇪 · Andreas Bauswein (2)🇬🇷 · Oliver Just (3,4)🇩🇪 · Else Pllumbi (3,5)🇩🇪 · Hans-Thomas Janka (3) ((1) ULB Brussels, (2) Univ. Thessaloniki, (3) MPI Astrophysics, Garching, (4) Max Planck/Princeton Center for Plasma Physics, (5) Physik Dept., TUM, Garching)🇩🇪
We investigate beta-interactions of free nucleons and their impact on the electron fraction (Y_e) and r-process nucleosynthesis in ejecta characteristic of binary neutron star mergers (BNSMs). For that we employ trajectories from a relativistic BNSM model to represent the density-temperature evolutions in our parametric study. In the high-density environment, positron captures decrease the neutron richness at the high temperatures predicted by the hydrodynamic simulation. Circumventing the complexities of modelling three-dimensional neutrino transport, (anti)neutrino captures are parameterized in terms of prescribed neutrino luminosities and mean energies, guided by published results and assumed as constant in time. Depending sensitively on the adopted neutrino-antineutrino luminosity ratio, neutrino processes increase Y_e to values between 0.25 and 0.40, still allowing for a successful r-process compatible with the observed solar abundance distribution and a significant fraction of the ejecta consisting of r-process nuclei. If the electron neutrino luminosities and mean energies are relatively large compared to the antineutrino properties, the mean Y_e might reach values >0.40 so that neutrino captures seriously compromise the success of the r-process. In this case, the r-abundances remain compatible with the solar distribution, but the total amount of ejected r-material is reduced to a few percent, because the production of iron-peak elements is favored. Proper neutrino physics, in particular also neutrino absorption, have to be included in BNSM simulations before final conclusions can be drawn concerning r-processing in this environment and concerning observational consequences like kilonovae, whose peak brightness and color temperature are sensitive to the composition-dependent opacity of the ejecta.
↳ astro-ph.SRastro-ph.HEnucl-thMNRAS(2015)·113 citations
10
Direct Evidence of Washing out of Nuclear Shell Effects
A. Chaudhuri · T.K. Ghosh · K. Banerjee · S. Bhattacharya · Jhilam Sadhukhan · C. Bhattacharya · S. Kundu · J. K. Meena · G. Mukherjee · R. Pandey · T.K. Rana · P. Roy and 3 other authors
Constraining excitation energy at which nuclear shell effect washes out has important implications on the production of super heavy elements and many other fields of nuclear physics research. We report the fission fragment mass distribution in alpha induced reaction on an actinide target for wide excitation range in close energy interval and show direct evidence that nuclear shell effect washes out at excitation energy ~40 MeV. Calculation shows that second peak of the fission barrier also vanishes around similar excitation energy.
↳ nucl-exnucl-thPRC(2015)·37 citations
11
A primordial r-process?
T. Rauscher · J. H. Applegate · J. J. Cowan · F.-K. Thielemann · M. Wiescher
Baryon density inhomogeneities in the early universe can give rise to a floor of heavy elements (up to $A \approx 270$ ) produced in a primordial r-process with fission cycling. A parameter study with variation of the global baryon to photon ratio $η$ , and under inclusion of neutron diffusion effects was performed. New results concerning the dependence of the results on nuclear physics parameters are presented.
↳ astro-ph.HEnucl-th0 citations
12
Determination of $U (1)_{A}$ restoration from pion and $a_{0}$ -meson screening masses: Toward the chiral regime
Masahiro Ishii🇯🇵 · Koji Yonemura🇯🇵 · Junichi Takahashi🇯🇵 · Hiroaki Kouno🇯🇵 · Masanobu Yahiro🇯🇵
We incorporate the effective restoration of $U (1)_{A}$ symmetry in the 2+1 flavor entanglement Polyakov-loop extended Nambu--Jona-Lasinio (EPNJL) model by introducing a temperature-dependent strength $K (T)$ to the Kobayashi-Maskawa-'t Hooft (KMT) determinant interaction. $T$ dependence of $K (T)$ is well determined from pion and $a_{0}$ -meson screening masses obtained by lattice QCD (LQCD) simulations with improved p4 staggered fermions. The strength is strongly suppressed in the vicinity of the pseudocritical temperature of chiral transition. The EPNJL model with the $K (T)$ well reproduces meson susceptibilities calculated by LQCD with domain-wall fermions. The model shows that the chiral transition is second order at the "light-quark chiral-limit" point where the light quark mass is zero and the strange quark mass is fixed at the physical value. This indicates that there exists a tricritical point. Hence the location is estimated.
↳ hep-phhep-latnucl-thPRD(2016)·19 citations
13
Ground-State Electromagnetic Moments of Calcium Isotopes
R. F. Garcia Ruiz🇧🇪 · M. L. Bissell🇧🇪 · K. Blaum🇩🇪 · N. Frommgen🇩🇪 · M. Hammen🇩🇪 · J. D. Holt🇩🇪 · M. Kowalska🇨🇭 · K. Kreim🇩🇪 · J. Menendez🇩🇪 · R. Neugart🇩🇪 · G. Neyens🇧🇪 · W. Nortershauser🇩🇪 and 6 other authors
High-resolution bunched-beam collinear laser spectroscopy was used to measure the optical hyperfine spectra of the $^{43 - 51}$ Ca isotopes. The ground state magnetic moments of $^{49, 51}$ Ca and quadrupole moments of $^{47, 49, 51}$ Ca were measured for the first time, and the $^{51}$ Ca ground state spin $I = 3/2$ was determined in a model-independent way. Our results provide a critical test of modern nuclear theories based on shell-model calculations using phenomenological as well as microscopic interactions. The results for the neutron-rich isotopes are in excellent agreement with predictions using interactions derived from chiral effective field theory including three-nucleon forces, while lighter isotopes illustrate the presence of particle-hole excitations of the $^{40}$ Ca core in their ground state.
↳ nucl-exnucl-thPRC(2015)·64 citations
14
Characterization of relativistic heavy-ion collisions at the Large Hadron Collider through temperature fluctuations
Sumit Basu🇮🇳 · Rupa Chatterjee🇮🇳 · Bastanta K. Nandi🇮🇳 · Tapan K. Nayak🇮🇳
We propose to characterize heavy-ion collisions at ultra-relativistic energies by using fluctuations of energy density and temperature. Temperature fluctuations on an event-by-event basis have been studied both in terms of global temperature of the event, and locally by constructing fluctuation maps in small phase space bins in each event. Global temperature fluctuations provide an estimation of the specific heat of the system. Local temperature fluctuations of the event may be ascribed to the remnants of initial energy density fluctuations. Together these two observables give an insight into the system created in heavy-ion collisions and its evolution. Event-by-event hydrodynamic calculations indeed provide adequate theoretical basis for understanding the origin of the fluctuations. We demonstrate the feasibility of studying global and local temperature fluctuations at the Large Hadron Collider energy by the use of AMPT event generator.
↳ nucl-exnucl-thSpringer Proc.Phys. 174 (2016) 189-194·8 citations
15
Exploring effects of magnetic field on the Hadron Resonance Gas
Abhijit Bhattacharyya🇮🇳 · Sanjay K. Ghosh🇮🇳 · Rajarshi Ray🇮🇳 · Subhasis Samanta🇮🇳
We present a study of the effects of magnetic fields on fluctuations and correlations in hadron resonance gas model. We find significant changes in the fluctuations of net baryon number, electric charge and strangeness. This is also reflected in various fluctuation ratios along the freezeout curve.
↳ hep-phnucl-thEPL(2016)·57 citations
16
Neutron drip transition in accreting and nonaccreting neutron star crusts
N. Chamel · A. F. Fantina · J. L. Zdunik · P. Haensel
The neutron-drip transition in the dense matter constituting the interior of neutron stars generally refers to the appearance of unbound neutrons as the matter density reaches some threshold density $ρ_{drip}$ . This transition has been mainly studied under the cold catalyzed matter hypothesis. However, this assumption is unrealistic for accreting neutron stars. After examining the physical processes that are thought to be allowed in both accreting and nonaccreting neutron stars, suitable conditions for the onset of neutron drip are derived and general analytical expressions for the neutron drip density and pressure are obtained. Moreover, we show that the neutron-drip transition occurs at lower density and pressure than those predicted within the mean-nucleus approximation. This transition is studied numerically for various initial composition of the ashes from X-ray bursts and superbursts using microscopic nuclear mass models.
↳ astro-ph.HEnucl-thPRC(2015)·55 citations

Affiliations

first authorsco-authorsvia INSPIRE