Nuclear Theory·nucl-th

Tuesday·December 4, 2018

10 papers—6 primary·4 cross-listed

01
$η$ photoproduction off the deuteron and low-energy $η$ -nucleon interaction
S.X. Nakamura (Univ. Cruzeiro do Sul)🇧🇷 · H. Kamano (RCNP, Osaka Univ.)🇯🇵 · T. Ishikawa (ELPH, Tohoku Univ.)🇯🇵
We study $η$ photoproduction off the deuteron ( $γ d \to η p n$ ) at a special kinematics: $\sim 0.94$ GeV of the photon beam energy and $\sim 0^{\circ}$ of the scattering angle of the proton. This kinematics is ideal to extract the low-energy $η$ -nucleon scattering parameters such as $a_{η N}$ (scattering length) and $r_{η N}$ (effective range) because the $η$ -nucleon elastic scattering is significantly enhanced. We show that if a ratio $R$ , the $γ d \to η p n$ cross section divided by the $γ p \to η p$ cross section convoluted with the proton momentum distribution in the deuteron, is measured with 5% error, $Re [a_{η N}]$ ( $Re [r_{η N}]$ ) can be determined at the precision of $\sim \pm$ 0.1 fm ( $\sim \pm$ 0.5 fm), significantly narrowing down the currently estimated range of the parameters. The measurement is ongoing at the Research Center for Electron Photon Science (ELPH), Tohoku University.
nucl-thhep-phnucl-exJPS Conf.Proc.(2019)·0 citations
02
Wigner function approach to polarization-vorticity coupling and hydrodynamics with spin
Avdhesh Kumar🇵🇱
Newly introduced equilibrium Wigner functions for particles with spin one-half are used in the semi-classical kinetic equations to study a possible relation between thermal vorticity and spin polarization. It is shown that in global equilibrium both the thermal-vorticity and spin polarization tensors are constant but not necessarily equal. In the case of local equilibrium, we define a procedure leading to hydrodynamic equations with spin. We introduce such equations for the de~Groot, van~Leeuwen, and van~Weert (GLW) formalism as well as for the canonical scheme (these two frameworks differ by the definitions of the energy-momentum and spin tensors). It is found that the GLW and canonical versions are connected by a pseudo-gauge transformation.
nucl-thhep-phPoS(2018)·6 citations
03
The production of $b b ˉ$ dijet in heavy-ion collisions at the LHC
Sa Wang🇨🇳 · Wei Dai🇨🇳 · Shan-Liang Zhang🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
We report our recent theoretical calculations for $b b ˉ$ dijet production in high-energy nuclear collisions. The NLO+parton shower (PS) event generator SHERPA has been employed to provide the pp baseline of $b b ˉ$ dijet production. A framework which combines Langevin transport equation to describe the evolution of heavy quarks and the higher-twist scheme to consider the inelastic energy loss of both light and heavy partons has been implemented. Within this framework, we present the theoretical result of transverse momentum imbalance $x_{J} = p_{T 1} / p_{T 2}$ both for inclusive dijet and $b b ˉ$ dijet in Pb+Pb collision at 5.02 TeV. The energy loss of b jet would shift $x_{J}$ to smaller value relative to p+p reference which is consistent with the CMS data. In addition, we show the medium modification for angular correlation of $b b ˉ$ dijet in A+A collision at $s_{N N} = 5.02$ ~TeV. We observe a stronger suppression in small $Δ ϕ = ∣ ϕ_{b 1} - ϕ_{b 2} ∣$ region where the gluon splitting processes dominate relative to large $Δ ϕ$ region. The difference leads to a modest suppression on near side ( $Δ ϕ \sim 0$ ) and enhancement on away side ( $Δ ϕ \sim π$ ).
nucl-thhep-phPoS(2018)·3 citations
04
Simultaneous Fitting of Neutron Star Structure and Cooling Data
Spencer Beloin🇺🇸 · Sophia Han🇺🇸 · Andrew W. Steiner🇺🇸 · Khorgolkhuu Odbadrakh🇺🇸
Using a model for the equation of state and composition of dense matter and the magnitude of singlet proton superconductivity and triplet neutron superfluidity, we perform the first simultaneous fit of neutron star masses and radii determined from observations of quiescent low-mass x-ray binaries and luminosities and ages determined from observations of isolated neutron stars. We find that the Vela pulsar strongly determines the values inferred for the superfluid/superconducting gaps and the neutron star radius. We find, regardless of whether or not the Vela pulsar is included in the analysis, that the threshold density for the direct Urca process lies between the central density of 1.7 and 2 solar mass neutron stars. We also find that two solar mass stars are unlikely to cool principally by the direct Urca process because of the suppression by neutron triplet superfluidity.
nucl-thastro-ph.HEastro-ph.SRPRC(2019)·23 citations
05
Application of resonant decay method for compound-systems at analysis inclusive spectra in high-energy nuclear reactions
S.A. Omelchenko · V.S. Olkhovsky
It is shown, that the exponential decrease of the energy spectra of the fragments with growing its energy, which does not depend from the fragment type, targets, projectiles and projectile energies, and which sometimes accompanied slight oscillations, can be explained by the phenomenon of time resonances. These time resonances correspond to decay of intermediate excited nuclear composite system. For the first time, expressions for the decay rate and the probability of survival of such system as a function of time are obtained. Inclusive spectra for two real high-energy nuclear reactions are calculated.
nucl-th0 citations
06
Single-particle structure of the N = 20 and N = 28 isotones within the dispersive optical model
O.V. Bespalova · A.A. Klimochkina
The neutron single-particle characteristics of the N = 20, 28 isotones at 8 < Z < 30 was calculated within the dispersive optical model. The global parameters of the spin-orbit and imaginary parts of the potential as well as surface absorption independent on neutron-proton asymmetry and increased diffuseness at large neutron excess were used in the calculations. The suitability of the global parameters to predict the evolution of the neutron single-particle structure of nuclei near the neutron drip line was investigated. The following results are in agreement with the available experimental data: the reduction of the particle-hole energy gaps, the degeneration of the 1f7/2 and 2p states and then a change in the 1f7/2 , 2p3/2 level sequence and more rapid reduction of the 2p-splitting in comparison with the 1f-splitting with decreasing Z. The predictive power of the dispersive optical model with respect to neutron-rich nuclei is demonstrated.
nucl-thMoscow Univ.Phys.Bull.(2018)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

η photoproduction off the deuteron and low-energy η-nucleon interaction

Wigner function approach to polarization-vorticity coupling and hydrodynamics with spin

The production of bbˉ dijet in heavy-ion collisions at the LHC

Simultaneous Fitting of Neutron Star Structure and Cooling Data

Application of resonant decay method for compound-systems at analysis inclusive spectra in high-energy nuclear reactions

Single-particle structure of the N = 20 and N = 28 isotones within the dispersive optical model

Affiliations

$η$ photoproduction off the deuteron and low-energy $η$ -nucleon interaction

The production of $b b ˉ$ dijet in heavy-ion collisions at the LHC