Nuclear Theory·nucl-th

Thursday·February 21, 2019

11 papers—5 primary·6 cross-listed

01
Green's function method for the spin and pseudospin symmetries in the single-particle resonant states
Ting-Ting Sun · Wan-Li Lu · Long Qian · Yu-Xiao Li
We investigate the spin and pseudospin symmetry in the single-particle resonant states by solving the Dirac equation containing a Woods-Saxon potential with Green's function method. Taking double-magic nucleus $^{208}$ Pb as an example, three spin doublets $3 d$ , $2 h$ , and $1 j$ and three pseudospin doublets $3 p ~$ , $1 i ~$ , and $1 j ~$ are obtained for the single-neutron resonant states. By analyzing the energy splittings, we find that the threshold effect plays an important role in resonant pseudospin doubles. Besides, there is a reversed level structure of pseudospin doublets in the continuum. Differently, all the width splittings of either the spin doublets or the pseudospin doublets are systematically positive and the splittings are very small except $1 j ~$ doublet. Further studies show that the splittings of the energies and widths for the resonant (pseudo)spin doublets are independent. Besides, the similarity properties of the wave functions of the spin and pseudospin doublets still maintain well in resonant states.
nucl-thPRC(2019)·21 citations
02
Continuum Skyrme-Hartree-Fock-Bogoliubov theory with Green's function method for odd- $A$ nuclei
Ting-Ting Sun · Zi-Xin Liu · Long Qian · Bing Wang · Wei Zhang
To study the exotic odd nuclear systems, the self-consistent continuum Skyrme-Hartree-Fock-Bogoliubov theory formulated with Green's function technique is extended to include blocking effects with the equal filling approximation. Detailed formula are presented.To perform the integrals of the Green's function properly, the contour paths $C_{b}^{-}$ and $C_{b}^{+}$ introduced for the blocking effects should include the blocked quasi-particle state but can not intrude into the continuum area. By comparing with the box-discretized calculations, the great advantages of the Green's function method in describing the extended density distributions, resonant states, and the couplings with the continuum in exotic nuclei are shown. Finally, taking the neutron-rich odd nucleus $^{159}$ Sn as an example, the halo structure is investigated by blocking the quasi-particle state $1 p_{1/2}$ . It is found that it is mainly the weakly bound states near the Fermi surface that contribute a lot for the extended density distributions at large coordinate space.
nucl-thPRC(2019)·15 citations
03
Benchmarking a Non-Equilibrium Approach to Photon Emission in Relativistic Heavy-Ion Collisions
Anna Schäfer🇩🇪 · Juan M. Torres-Rincon🇺🇸 · Jonas Rothermel🇩🇪 · Niklas Ehlert🇩🇪 · Charles Gale🇨🇦 · Hannah Elfner🇩🇪
In this work, the production of photons through binary scattering processes is investigated for equilibrated hadronic systems. More precisely, a non-equilibrium hadronic transport approach to describe relativistic heavy-ion collisions is benchmarked with respect to photon emission. Cross sections for photon production in $π + ρ \to π + γ$ and $π + π \to ρ + γ$ scattering processes are derived from an effective chiral field theory and implemented into the hadronic transport approach, SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). The implementation is verified by systematically comparing the thermal photon rate to theoretical expectations. Further, the impact of form factors is discussed, scattering processes mediated by $ω$ mesons are found to contribute significantly to the total photon production. Several comparisons of the yielded photon rates are performed: to parametrizations of the very same rates, as used in hydrodynamic simulations, to previous works relying on different cross sections for the production of direct photons from the hadronic stage, and to partonic rates. Finally, the impact of considering the finite width of the $ρ$ meson is investigated, where a significant enhancement of photon production in the low-energy region is observed. This benchmark is the first step towards a consistent treatment of photon emission in hybrid hydrodynamics+transport approaches and a genuine dynamical description.
nucl-thhep-phnucl-exPRD(2019)·26 citations
04
A systematic study of the factors affecting central depletion in nuclei
G. Saxena · M. Kumawat · B. K. Agrawal · Mamta Aggarwal
A systematic study of the central depletion of proton density has been performed in the isotonic chains of nuclei with neutron numbers $N = 20$ and $28$ using different variants of the relativistic mean-field (RMF) models. These models include either the non-linear contributions from the mesons with the coupling constants being density independent or the non-linearity of the mesonic fields realized through the density dependent coupling strengths. The central depletion in deformed nuclei tends to disappear irrespective of the occupancy of $2 s_{1/2}$ state in contrast to the spherical nuclei in which the unoccupancy of $2 s_{1/2}$ state leads to the central depletion. Due to the differences in the strength of spin-orbit potentials in these models, the central depletions are found to be model dependent. The influence of the central depletion on the neutron-skin thickness is also investigated. It appears that the effects of the central depletion do not percolate far enough to display its finger prints on the trends of the neutron-skin thickness.
nucl-thJ.Phys.G(2019)·13 citations
05
Calculation of an $A = 3$ bound-state matrix element in pionless effective field theory
Hilla De-Leon🇮🇱 · Lucas Platter🇺🇸 · Doron Gazit🇮🇱
In this paper, we establish a general framework for calculating pionless matrix elements between $A = 3$ bound-states up to next-to-leading-order. This framework is useful for pionless calculations of electroweak observables, such as $^{3}$ H, $^{3}$ He magnetic moments and $^{3}$ H $β$ decay. Starting from a Bethe-Salpeter equation, we prove that for a bound-state, the three-nucleon wave-function normalization can be expressed diagrammatically in a way that is equivalent to the unit operator between two identical three-nucleon bound-states. This diagrammatic form of the identity matrix element is the foundation for constructing an $A = 3$ matrix element of a general operator. We show that this approach can be used to calculate the energy difference between $^{3}$ H and $^{3}$ He due to the Coulomb interaction, and to calculate the NLO corrections to the $^{3}$ H and $^{3}$ He scattering amplitudes due to effective range corrections.
nucl-th4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Green's function method for the spin and pseudospin symmetries in the single-particle resonant states

Continuum Skyrme-Hartree-Fock-Bogoliubov theory with Green's function method for odd-A nuclei

Benchmarking a Non-Equilibrium Approach to Photon Emission in Relativistic Heavy-Ion Collisions

A systematic study of the factors affecting central depletion in nuclei

Calculation of an A=3 bound-state matrix element in pionless effective field theory

Affiliations

Continuum Skyrme-Hartree-Fock-Bogoliubov theory with Green's function method for odd- $A$ nuclei

Calculation of an $A = 3$ bound-state matrix element in pionless effective field theory