Nuclear Theory·nucl-th

Tuesday·June 7, 2022

11 papers—6 primary·5 cross-listed

01
Ratios of collective flow observables in high-energy isobar collisions are insensitive to final state interactions
Chunjian Zhang🇺🇸 · Somadutta Bhatta🇺🇸 · Jiangyong Jia🇺🇸
The ratios of bulk observables, such as harmonic flow $v_{2}$ and $v_{3}$ , between high-energy $^{96}$ Ru+ $^{96}$ Ru and $^{96}$ Zr+ $^{96}$ Zr collisions were recently argued to be a clean probe of the nuclear structure differences between $^{96}$ Ru and $^{96}$ Zr. Using a transport model simulation of isobar collisions, we quantify this claim from the dependence of the ratios $v_{2, Ru} / v_{2, Zr}$ and $v_{3, Ru} / v_{3, Zr}$ on various final state effects, such as the shear viscosity, hadronization and hadronic cascade. Although the $v_{2}$ and $v_{3}$ change by more than 50% when varying the final state effects, the ratios are unchanged. In addition, these ratios are independent of the transverse momentum $p_{T}$ and hadron species, despite of up to a factor of two change in $v_{n}$ . The ratio of mean transverse momentum $⟨ p_{T} ⟩$ is found to be controlled by the nuclear skin and nuclear radius, but is only slightly impacted by the final state effects. Therefore, these isobar ratios serve as a clean probe of the initial condition of the quark-gluon plasma, which in turn is controlled by the collective structure of the colliding nuclei.
nucl-thhep-exhep-phnucl-exPRC(2022)·42 citations
02
Extended optimal Fermi averaging for near-recoilless $Λ$ production in the ( $K^{-}$ , $π^{-}$ ) reaction on nuclei
Toru Harada🇯🇵 · Yoshiharu Hirabayashi🇯🇵
We propose to extend the optimal Fermi averaging procedure theoretically in order to calculate an in-medium $K^{-} n \to π^{-} Λ$ amplitude for the exothermic ( $K^{-}$ , $π^{-}$ ) reaction on nuclei in the framework of a distorted-wave impulse approximation, taking into account the local momentum transfer generated by semiclassical distorted waves for $K^{-}$ and $π^{-}$ mesons. Angular distributions for the $^{12}$ C( $K^{-}$ , $π^{-}$ ) $_{Λ}^{12}$ C reaction in which a momentum transfer is $q ≲$ 80 MeV/ $c$ at $p_{K} =$ 800 MeV/ $c$ in the $π^{-}$ forward direction, are estimated by applying the extended procedure. The result shows that the calculated angular distributions are in good agreement with those of the data, and this extension is a successful prescription making it possible to describe the reaction cross sections in near-recoilless reactions such as ( $K^{-}$ , $π^{-}$ ) in our framework.
nucl-thnucl-exPRC(2022)·4 citations
03
Relativistic Mean Field Study of Neutron Stars and Hyperon Stars
Ishfaq Ahmad Rather🇮🇳
This thesis focuses on a variety of active research topics, such as nuclear matter, neutron stars, and phase transition within the framework of the RMF model. We use the previously successful effective field theory-driven Relativistic Mean Field (RMF) and density-dependent RMF (DD-RMF)formalisms for analyzing hadron matter to examine the infinite nuclear matter and neutron stars. The presence of exotic phases such as quarks has been investigated using the MIT Bag model and its variants, such as the vBag model, at various bag constants. The other exotic phases, such as hyperons, have also been studied under the influence of a strong magnetic field.
nucl-thastro-ph.HEgr-qc2 citations
04
Deep learning assisted jet tomography for the study of Mach cones in QGP
Zhong Yang🇨🇳 · Yayun He🇨🇳 · Wei Chen🇨🇳 · Wei-Yao Ke🇺🇸 · Long-Gang Pang🇨🇳 · Xin-Nian Wang🇨🇳
Mach cones are expected to form in the expanding quark-gluon plasma (QGP) when energetic quarks and gluons (called jets) traverse the hot medium at a velocity faster than the speed of sound in high-energy heavy-ion collisions. The shape of the Mach cone and the associated diffusion wake are sensitive to the initial jet production location and the jet propagation direction relative to the radial flow because of the distortion by the collective expansion of the QGP and large density gradient. The shape of jet-induced Mach cones and their distortions in heavy-ion collisions provide a unique and direct probe of the dynamical evolution and the equation of state of QGP. However, it is difficult to identify the Mach cone and the diffusion wake in current experimental measurements of final hadron distributions because they are averaged over all possible initial jet production locations and propagation directions. To overcome this difficulty, we develop a deep learning assisted jet tomography which uses the full information of the final hadrons from jets to localize the initial jet production positions. This method can help to constrain the initial regions of jet production in heavy-ion collisions and enable a differential study of Mach-cones with different jet path length and orientation relative to the radial flow of the QGP in heavy-ion collisions.
nucl-thEPJC(2023)·34 citations
05
Comprehensive simulation of heavy-ion collisions at non-zero baryon chemical potential
A. De🇺🇸 · J. I. Kapusta🇺🇸 · M. Singh🇺🇸 · T. Welle🇺🇸
We present results of hydrodynamic modelling of Au-Au collisions from $s_{N N}$ = 7.7 to 200 GeV. Our simulations have three novel components. Firstly, we use a Linear EXtrapolation of Ultrarelativistic nucleon-nucleon Scattering to nucleus-nucleus collisions (LEXUS) inspired Monte-Carlo initial state model. Secondly, we use a crossover equation of state at finite baryon densities without a critical point. Finally, we use departure functions derived from the quasiparticle theory of transport coefficients for hadronic matter at non-zero baryon densities.
nucl-thhep-phPRC(2022)·17 citations
06
Relation to a property of the angular momentum zero space of states of four fermions in an angular momentum $j = 9/2$ shell unexpectedly found to be stationary for any rotationally invariant two-body interaction
K. Neergård
The existence of states with angular momenta $I = 4$ and~6 of four fermions in an angular momentum $j = 9/2$ shell that are stationary for any rotationally invariant two-body interaction despite the presence of other states with the same angular momentum, the Escuderos-Zamick states, is shown to be equivalent to the invariance to any such interaction of the span of states generated from $I = 0$ states by one-body operators. This invariance is verified by exact calculation independently of previous verifications of the equivalent statement. It explains the occurrence of the Escuderos-Zamick states for just $I = 4$ and 6. The action of an arbitrary interaction on the invariant space and its orthogonal complement is analyzed, leading to a relation of the Escuderos-Zamick energy levels to levels with $I = 10$ and 12. Parts of the observed spectra of $^{72}$ Ni, $^{74}$ Ni, $^{94}$ Ru, $^{96}$ Pd, $^{212}$ Rn, and $^{214}$ Ra are discussed in the light of this relation.
nucl-thnucl-exPRC(2022)·4 citations
07
Collision of localized shocks in AdS $_{5}$ as a series expansion in transverse gradients
Sebastian Waeber🇺🇸 · Laurence G. Yaffe🇺🇸
We introduce a computational framework to more efficiently calculate the collision of localized shocks in five dimensional asymptotically Anti-de Sitter space. We expand the Einstein equations in transverse gradients and find that our numerical results agree well with exact solutions already at first order in the expansion. Moreover, the Einstein equations at first order in transverse gradients can be decoupled into two sets of differential equations. The bulk fields of one of these sets has only a negligible contribution to boundary observables, such that the computation on each time slice can be simplified to the solution of several planar shockwave equations plus four further differential equations for each transverse plane `pixel'. At the cost of errors of $≲ 10%$ at the hydrodynamization time and for low to mid rapidities, useful numerical solutions can be sped up by roughly one order of magnitude.
↳ hep-thgr-qcnucl-thJHEP(2022)·4 citations
08
A holographic bottom-up description of light nuclide spectroscopy and stability
Miguel Angel Martin Contreras🇨🇱 · Saulo Diles🇨🇱 · Alfredo Vega🇧🇷
This work explores a holographic proposal to describe light nuclide spectroscopy by considering extensions to the well-known bottom-up AdS/QCD proposals, the hardwall and softwall models. We also propose an alternative description inspired by the Woods-Saxon potential. We find the static dilaton associated with this potential in this Wood-Saxon-like model. We compute the nuclide spectra finding that, despite their pure AdS/QCD origin, hardwall and softwall, as monoparametric models, have good accuracy and precision since the RMS error is near 11 $%$ and 4 $%$ respectively. In the case of the Wood-Saxon model, the RMS was around 1 $%$ . We also discuss configurational entropy as a tool to categorize which model is suitable to describe nuclides in terms of stability. We found that configurational entropy resembles a stability line, independent from nuclear spin, for symmetric light nuclides when considering softwall and Wood-Saxon-like models. For the hardwall case, configurational entropy, despite increasing with the constituent number, depends on the nuclear spin. Thus, the Woods-Saxon-like model emerges as the best choice to describe light nuclide spectroscopy in the bottom-up scenario.
↳ hep-phhep-thnucl-thPLB(2022)·13 citations
09
Open charm and bottom meson-nucleon potentials à la nuclear force
Yasuhiro Yamaguchi🇯🇵 · Shigehiro Yasui🇯🇵 · Atsushi Hosaka🇯🇵
We discuss the interaction of an open heavy meson ( $D ˉ$ and $D ˉ^{*}$ for charm or $B$ and $B^{*}$ for bottom) and a nucleon ( $N$ ) by considering the $π$ , $σ$ , $ρ$ , and $ω$ exchange potentials. We construct a potential model by respecting chiral symmetry for light quarks and spin symmetry for heavy quarks. Model parameters are adjusted by referring the phenomenological nuclear (CD-Bonn) potentials reproducing the low-energy $N N$ scatterings. We show that the resulting interaction may accommodate $D ˉ N$ and $B N$ bound states with quantum number $I (J^{P}) = 0 (1/ 2^{-})$ , and a $B N$ bound state with $I (J^{P}) = 1 (1/ 2^{-})$ . We find that, in the present potential model, the $σ$ exchange potential plays an important role.
↳ hep-phnucl-thPRD(2022)·9 citations
10
Do we need dense matter equation of state in curved spacetime for neutron stars?
Jianing Li🇨🇳 · Tao Guo🇨🇳 · Jiaxing Zhao🇨🇳 · Lianyi He🇨🇳
Neutron stars are regarded as natural laboratories for the study of dense strong interaction matter. The equation of state (EoS) of dense matter computed in flat spacetime is used to predict the structure of neutron stars by solving the Tolman-Oppenheimer-Volkoff (TOV) equation. Recently, it has been reported that the curved spacetime effect or specifically gravitational time dilation effect on the EoS of dense matter leads to a significant increase of the maximum mass limit of neutron stars [Phys. Rev. D \textbf{104}, 123005 (2021) and J. Cosmol. Astropart. Phys. 02 (2021) 026]. However, in this work, we show that to study the hydrostatic equilibrium of dense matter within the framework of general relativity and relativistic fluid dynamics, the grand canonical EoS of dense matter, $p (T, μ)$ , should be the same as that computed in flat spacetime, otherwise it is not consistent with local thermodynamic relations and energy-momentum conservation of the fluid. The gravitation influences the pressure $p$ only through enhancing the temperature $T$ and the chemical potential $μ$ , known as Tolman's law and Klein's law. We rewrite the TOV equation as an alternative version so that the grand canonical EoS computed by using field theoretical methods can be used as a direct input. This may provide a tool to study the grand canonical EoS of dense matter via deep learning.
↳ gr-qcastro-ph.HEhep-phnucl-thPRD(2022)·16 citations
11
Impact of Dynamical Fermions on the Centre Vortex Gluon Propagator
James Biddle🇦🇺 · Waseem Kamleh🇦🇺 · Derek Leinweber🇦🇺
The impact of $S U (3)$ centre vortices on the Landau-gauge gluon propagator is calculated in the presence of dynamical fermions and compared to the pure Yang-Mills case. The presence of dynamical fermions is found to alter the behaviour of the centre vortex propagator when compared to the established pure-gauge result. The gluon spectral representation is also explored from the centre vortex perspective, where centre vortices are shown to exhibit clear signs of positivity violation, which is an indicator of confinement. Vortex removal subsequently restores positivity, demonstrating the crucial role centre vortices play in the confinement of gluons.
↳ hep-latnucl-thPRD(2022)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE