Nuclear Theory·nucl-th

Monday·July 5, 2021

5 papers—2 primary·3 cross-listed

01
Isovector giant monopole and quadrupole resonances in a Skyrme energy density functional approach with axial symmetry
Kenichi Yoshida
[Background] Giant resonance (GR) is a typical collective mode of vibration. The deformation splitting of the isovector (IV) giant dipole resonance is well established. However, the splitting of GRs with other multipolarities is not well understood. [Purpose] I explore the IV monopole and quadrupole excitations and attempt to obtain the generic features of IV giant resonances in deformed nuclei by investigating the neutral and charge-exchange channels simultaneously. [Method] I employ a nuclear energy-density functional (EDF) method: the Skyrme-Kohn-Sham-Bogoliubov and the quasiparticle random-phase approximation are used to describe the ground state and the transition to excited states. [Results] I find the concentration of the monopole strengths in the energy region of the isobaric analog or Gamow-Teller resonance irrespective of nuclear deformation, and the appearance of a high-energy giant resonance composed of the particle-hole configurations of $2ℏ ω_{0}$ excitation. Splitting of the distribution of the strength occurs in the giant monopole and quadrupole resonances due to deformation. The lower $K$ states of quadrupole resonances appear lower in energy and possess the enhanced strengths in the prolate configuration, and vice versa in the oblate configuration, while the energy ordering depending on $K$ is not clear for the $J = 1$ and $J = 2$ spin-quadrupole resonances. [Conclusions] The deformation splitting occurs generously in the giant monopole and quadrupole resonances. The $K$ -dependence of the quadrupole transition strengths is largely understood by the anisotropy of density distribution.
nucl-thnucl-exPRC(2021)·3 citations
02
Constraints on the $Λ$ -neutron interaction from charge symmetry breaking in the $_{Λ}^{4} He$ -- $_{Λ}^{4} H$ hypernuclei
Johann Haidenbauer🇩🇪 · Ulf-G. Meißner🇩🇪 · Andreas Nogga🇩🇪
We utilize the experimentally known difference of the $Λ$ separation energies of the mirror hypernuclei $_{Λ}^{4} He$ and $_{Λ}^{4} H$ to constrain the $Λ$ -neutron interaction. We include the leading charge-symmetry breaking (CSB) interaction into our hyperon-nucleon interaction derived within chiral effective field theory at next-to-leading order. In particular, we determine the strength of the two arising CSB contact terms by a fit to the differences of the separation energies of these hypernuclei in the $0^{+}$ and $1^{+}$ states, respectively. By construction, the resulting interaction describes all low energy hyperon-nucleon scattering data, the hypertriton and the CSB in $_{Λ}^{4} He$ - $_{Λ}^{4} H$ accurately. This allows us to provide first predictions for the $Λ$ n scattering lengths, based solely on available hypernuclear data.
nucl-thFew Body Syst.(2021)·27 citations
03
Shared Data and Algorithms for Deep Learning in Fundamental Physics
Lisa Benato · Erik Buhmann · Martin Erdmann · Peter Fackeldey · Jonas Glombitza · Nikolai Hartmann · Gregor Kasieczka · William Korcari · Thomas Kuhr · Jan Steinheimer · Horst Stöcker · Tilman Plehn · Kai Zhou
We introduce a Python package that provides simply and unified access to a collection of datasets from fundamental physics research - including particle physics, astroparticle physics, and hadron- and nuclear physics - for supervised machine learning studies. The datasets contain hadronic top quarks, cosmic-ray induced air showers, phase transitions in hadronic matter, and generator-level histories. While public datasets from multiple fundamental physics disciplines already exist, the common interface and provided reference models simplify future work on cross-disciplinary machine learning and transfer learning in fundamental physics. We discuss the design and structure and line out how additional datasets can be submitted for inclusion. As showcase application, we present a simple yet flexible graph-based neural network architecture that can easily be applied to a wide range of supervised learning tasks. We show that our approach reaches performance close to dedicated methods on all datasets. To simplify adaptation for various problems, we provide easy-to-follow instructions on how graph-based representations of data structures, relevant for fundamental physics, can be constructed and provide code implementations for several of them. Implementations are also provided for our proposed method and all reference algorithms.
↳ cs.LGastro-ph.IMhep-phnucl-th+2Comput.Softw.Big Sci.(2022)·19 citations
04
Post-explosion evolution of core-collapse supernovae
M. Witt · A. Psaltis · H. Yasin · C. Horn · M. Reichert · T. Kuroda · M. Obergaulinger · S. M. Couch · A. Arcones
We investigate the post-explosion phase in core-collapse supernovae with 2D hydrodynamical simulations and a simple neutrino treatment. The latter allows us to perform 46 simulations and follow the evolution of the 32 successful explosions during several seconds. We present a broad study based on three progenitors (11.2 $M_{⊙}$ , 15 $M_{⊙}$ , and 27 $M_{⊙}$ ), different neutrino-heating efficiencies, and various rotation rates. We show that the first seconds after shock revival determine the final explosion energy, remnant mass, and properties of ejected matter. Our results suggest that a continued mass accretion increases the explosion energy even at late times. We link the late-time mass accretion to initial conditions such as rotation strength and shock deformation at explosion time. Only some of our simulations develop a neutrino-driven wind that survives for several seconds. This indicates that neutrino-driven winds are not a standard feature expected after every successful explosion. Even if our neutrino treatment is simple, we estimate the nucleosynthesis of the exploding models for the 15 $M_{⊙}$ progenitor after correcting the neutrino energies and luminosities to get a more realistic electron fraction.
↳ astro-ph.HEastro-ph.SRnucl-thApJ(2021)·27 citations
05
X(3872) Production in Relativistic Heavy-Ion Collisions
Baoyi Chen🇨🇳 · Liu Jiang🇨🇳 · Xiao-Hai Liu🇨🇳 · Yunpeng Liu🇨🇳 · Jiaxing Zhao🇨🇳
Heavy-ion collisions provide a unique opportunity to study the nature of X(3872) compared with electron-positron and proton-proton (antiproton) collisions. We investigate the centrality and momentum dependence of X(3872) in heavy-ion collisions via the Langevin equation and instant coalescence model (LICM). When X(3872) is treated as a compact tetraquark state, the tetraquarks are produced via the coalescence of heavy and light quarks near the quantum chromodynamic (QCD) phase transition due to the restoration of the heavy quark potential at $T \to T_{c}$ . In the molecular scenario, loosely bound X(3872) is produced via the coalescence of $D^{0}$ - $D ˉ^{* 0}$ mesons in a hadronic medium after kinetic freeze-out. We employ the LICM to explain both $D^{0}$ and $J / ψ$ production as a benchmark. Then we give predictions regarding X(3872) production and the nuclear modification factor $R_{AA}^{X (3872)}$ . We find that the total yield of tetraquark is several times larger than the molecular production in Pb-Pb collisions. Although the geometric size of the molecule is huge, the coalescence probability is small due to strict constraints on the relative momentum between $D^{0}$ and $D ˉ^{* 0}$ in the molecular Wigner function, which significantly suppresses the molecular yield.
↳ hep-phnucl-thPRC(2022)·44 citations

Affiliations

first authorsco-authorsvia INSPIRE

Isovector giant monopole and quadrupole resonances in a Skyrme energy density functional approach with axial symmetry

Constraints on the Λ-neutron interaction from charge symmetry breaking in the Λ4​He--Λ4​H hypernuclei

Shared Data and Algorithms for Deep Learning in Fundamental Physics

Post-explosion evolution of core-collapse supernovae

X(3872) Production in Relativistic Heavy-Ion Collisions

Affiliations

Constraints on the $Λ$ -neutron interaction from charge symmetry breaking in the $_{Λ}^{4} He$ -- $_{Λ}^{4} H$ hypernuclei