Nuclear Theory·nucl-th

Monday·April 16, 2018

14 papers—8 primary·6 cross-listed

01
Nuclear applications of ANL-Osaka amplitudes: pion photo-productions on deuteron
S.X. Nakamura (Univ. Cruzeiro do Sul)🇧🇷 · H. Kamano (RCNP)🇯🇵 · T.-S. H. Lee (Argonne Nat'l Lab)🇺🇸 · T. Sato (RCNP, J-PARC)🇯🇵
The Argonne National Laboratory-Osaka University (ANL-Osaka) amplitudes (http://www.phy.anl.gov/theory/research/anl-osaka-pwa/) are applied to study pion photo-production reactions on the deuteron target. Within the multiple scattering formulation, we predict the cross sections of $d (γ, π) N N$ in the nucleon resonance region. The calculations include the impulse term and the final-state interaction (FSI) terms due to pion-exchange and nucleon-exchange. We show that the off-shell effects, calculated from the meson-exchange mechanisms, on the propagations of the exchanged nucleon and pion are significant in determining the reaction amplitudes. The FSI effects on the predicted cross sections are found to be important at energies near the $Δ$ (1232) resonance, and are still significant at higher energies. The results are in good agreement with most of the available data of $d (γ, π^{0}) n p$ and $d (γ, π^{-}) pp$ reactions.
nucl-thhep-phnucl-ex15 citations
02
Hydrodynamic attractor and the fate of perturbative expansions in Gubser flow
Gabriel Denicol🇧🇷 · Jorge Noronha🇧🇷
Perturbative expansions, such as the well-known gradient series and the recently proposed slow-roll expansion, have been recently used to investigate the emergence of hydrodynamic behavior in systems undergoing Bjorken flow. In this paper we determine for the first time the large order behavior of these perturbative expansions in relativistic hydrodynamics in the case of Gubser flow. While both series diverge, the slow-roll series can provide a much better overall description of the system's dynamics than the gradient expansion when both series are truncated at low orders. The truncated slow-roll series can also describe the attractor solution of Gubser flow as long as the system is sufficiently close to equilibrium near the origin (i.e., $ρ = 0$ ) in $d S_{3} \otimes R$ . Differently than the case of Bjorken flow, here we show that the Gubser flow attractor solution is not solely a function of the effective Knudsen number $τ_{R} σ_{μν} σ^{μν} \sim τ_{R} tanh ρ$ . Our results give further support to the idea that new \emph{resummed} constitutiv relations between dissipative currents and the gradients of conserved quantities can emerge in systems far from equilibrium that are beyond the regime of validity of the usual gradient expansion.
nucl-thhep-phhep-thPRD(2019)·73 citations
03
On the spin-isospin decomposition of nuclear symmetry energy
Wenmei Guo · M. Colonna · V. Greco · U. Lombardo · H. J. Schulze
The decomposition of nuclear symmetry energy into spin and isospin components is discussed to elucidate the underlying properties of the NN bare interaction. This investigation was carried out in the framework of the Brueckner-Hartree-Fock theory of asymmetric nuclear matter with consistent two and three body forces. It is shown the interplay among the various two body channels in terms of isospin singlet and triplet components as well as spin singlet and triplet ones. The broad range of baryon densities enables to study the effects of three body force moving from low to high densities.
nucl-thCPC(2020)·2 citations
04
Three-level mixing model for nuclear chiral rotation: Role of planar component
Q. B. Chen · K. Starosta · T. Koike
Three- and two-level mixing models are proposed to understand the doubling of states at the same spin and parity in triaxially-deformed atomic nuclei with odd numbers of protons and neutrons. The Particle-Rotor Model for such nuclei is solved using the newly proposed basis which couples angular momenta of two valence nucleons and the rotating triaxial mean-field into left-handed $∣ L ⟩$ , right-handed $∣ R ⟩$ , and planar $∣ P ⟩$ configurations. The presence and the impact of the planar component is investigated as a function of the total spin for mass A $\approx$ 130 nuclei with the valence h $_{11/2}$ proton particle, valence h $_{11/2}$ neutron hole and the maximum difference between principle axes allowed by the quadrupole deformation of the mean field. It is concluded that at each spin value the higher-energy member of a doublet of states is built on the anti-symmetric combination of $∣ L ⟩$ and $∣ R ⟩$ and is free of the $∣ P ⟩$ component, indicating that it is of pure chiral geometry. For the lower-energy member of the doublet, the contribution of the $∣ P ⟩$ component to the eigenfunction first decreases and then increases as a function of the total spin. This trend as well as the energy splitting between the doublet states are both determined by the Hamiltonian matrix elements between the planar ( $∣ P ⟩$ ) and non-planar ( $∣ L ⟩$ and $∣ R ⟩$ ) subspaces of the full Hilbert space.
nucl-thnucl-exPRC(2018)·18 citations
05
Interplay of drag by hot matter and electromagnetic force on the directed flow of heavy quarks
Sandeep Chatterjee🇵🇱 · Piotr Bozek🇵🇱
Rapidity-odd directed flow in heavy ion collisions can originate from two very distinct sources in the collision dynamics i. an initial tilt of the fireball in the reaction plane that generates directed flow of the constituents independent of their charges, and ii. the Lorentz force due to the strong primordial electromagnetic field that drives the flow in opposite directions for constituents carrying unlike sign charges. We study the directed flow of open charm mesons $D^{0}$ and $D^{0}$ in the presence of both these sources of directed flow. The drag from the tilted matter dominates over the Lorentz force resulting in same sign flow for both $D^{0}$ and $D^{0}$ , albeit of different magnitudes. Their average directed flow is about ten times larger than their difference. This charge splitting in the directed flow is a sensitive probe of the electrical conductivity of the produced medium. We further study their beam energy dependence; while the average directed flow shows a decreasing trend, the charge splitting remains flat from $s_{N N} = 60$ GeV to $5$ TeV.
nucl-thhep-phnucl-exPLB(2019)·75 citations
06
Radial flow in a multi phase transport model at FAIR energies
Soumya Sarkar🇮🇳 · Provash Mali🇮🇳 · Somnath Ghosh🇮🇳 · Amitabha Mukhopadhyay🇮🇳
Azimuthal distributions of radial velocities of charged hadrons produced in nucleus-nucleus $(A B)$ collisions are compared with the corresponding azimuthal distribution of charged hadron multiplicity in the framework of a multiphase transport (AMPT) model at two different collision energies. The mean radial velocity seems to be a good probe for studying radial expansion. While the anisotropic part of the distributions indicates a kind of collective nature of radial expansion, the isotropic part characterizes a thermal motion. The present investigation is carried out keeping the upcoming Compressed Baryonic Matter (CBM) experiment to be held at the Facility for Anti-proton Ion Research (FAIR) in mind. As far as high-energy heavy-ion interactions are concerned, CBM will supplement the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) experiments. In this context our simulation results at high baryochemical potential would be interesting, when scrutinized from the perspective of almost a baryon free environment achieved at RHIC and LHC.
nucl-thhep-phAdv.High Energy Phys.(2018)·1 citation
07
Shell-model interactions from chiral effective field theory
Lukas Huth · Victoria Durant · Johannes Simonis · Achim Schwenk
We construct valence-space Hamiltonians for use in shell-model calculations, where the residual two-body interaction is based on symmetry principles and the low-momentum expansion from chiral effective field theory. In addition to the usual free-space contact interactions, we also include novel center-of-mass--dependent operators that arise due to the Galilean invariance breaking by in-medium effects. We fitted the low-energy constants to 441 ground- and excited-state energies in the sd shell and obtained a root-mean-square derivation of 1.8 MeV at leading order and of 0.5 MeV at next-to-leading order, with natural low-energy constants in all cases. The developed chiral shell-model interactions enable order-by-order uncertainty estimates and show promising predictions for neutron-rich isotopes beyond the fitted data set.
nucl-thnucl-exPRC(2018)·26 citations
08
Charge symmetry violation in the doubly charmed cascade masses
K. K. Cushman🇦🇺 · A. W. Thomas🇦🇺 · R. D. Young🇦🇺
We investigate the electromagnetic contribution to the charge symmetry breaking in the $Ξ_{cc}$ baryon masses using a subtracted dispersion relation based on the Cottingham formula, following the formalism developed in an analysis of the octet baryon mass differences. In the absence of experimental information on the structure of charmed baryons, we use parameters for the electromagnetic structure of the $Ξ_{cc}$ and the difference in its charge states obtained from lattice QCD and estimates of SU(4) symmetry breaking. We report a conservative estimate for the mass splitting of the doubly charmed cascades to be 8 $\pm$ 9 MeV. While a smaller isospin splitting is compatible with this result, surprisingly it does not preclude the large splitting reported by the SELEX Collaboration. We identify those quantities which could be determined from lattice QCD and which would reduce the quoted theoretical uncertainty.
nucl-thhep-ph2 citations

Affiliations

first authorsco-authorsvia INSPIRE