Nuclear Theory·nucl-th

Monday·August 21, 2023

17 papers—8 primary·9 cross-listed

01
Novel approach to the removal of the Pauli-forbidden states in the orthogonality condition model: A case of multi- $α$ systems
H. Moriya · W. Horiuchi · B. Zhou
We propose to use a basis function constructed based on the microscopic cluster model for an efficient description of multi-cluster systems with the orthogonality condition originating from the Pauli principle. The basis function is expressed analytically by a superposition of correlated Gaussian functions. We demonstrate the power of this approach by taking an example of a $3 α$ system, $^{12}$ C. A comparison with the conventional pseudopotential method using the projection operator is made. The present method offers efficient and numerically stable computations as the number of basis functions is significantly reduced compared to the conventional method. We show that the present basis function includes reasonably small components of the Pauli-forbidden states, allowing us to discuss simply the structure of the first excited $0^{+}$ state, Hoyle state.
nucl-thEPJA(2023)·2 citations
02
Nuclear matrix elements calculation for $0 ν β β$ decay of $^{124}$ Sn using nonclosure approach in nuclear shell model
Shahariar Sarkar🇮🇳 · P. K. Rath🇮🇳 · V. Nanal🇮🇳 · R. G. Pillay🇮🇳 · Pushpendra P. Singh🇮🇳 · Y. Iwata🇯🇵 · K. Jha🇮🇳 · P. K. Raina🇮🇳
In this study, we calculate the nuclear matrix elements (NMEs) for the light neutrino-exchange mechanism of neutrinoless double beta $0 ν β β$ ) decay of $^{124}$ Sn within the framework of the interacting nuclear shell model using the effective shell model Hamiltonian GCN5082. A novel method based on a nonclosure approach is employed, wherein for the intermediate nucleus $^{124}$ Sb, effects of energy of 100 states for each $J_{k}^{π}$ = $0^{+}$ to $1 1^{+}$ and $2^{-}$ to $9^{-}$ ( $Δ J_{k}$ =1) are explicitly included in the NMEs calculation. Other common effects such as the finite size of nucleons, higher-order effects of nucleon currents, and short-range correlations (SRC) of nucleons are also taken into account. The extracted optimal closure energy is 2.9 MeV for a total NME of $^{124}$ Sn $0 ν β β$ decay, which is independent of different forms of SRC parametrizations. A comparison of NMEs and half-lives with some of the recent calculations is presented. Further, to gain a comprehensive understanding of the role of nuclear structure on the $0 ν β β$ decay, the dependence of NMEs on spin-parity of the intermediate states, coupled spin-parity of neutrons and protons, and the number of intermediate states, is explored. It is observed that the inclusion of the effects of excitation energies of the intermediate nucleus yields more reliable NMEs. The present findings provide valuable insights for experimental investigations of $0 ν β β$ decay of $^{124}$ Sn in India and elsewhere.
nucl-thPRC(2024)·4 citations
03
Tetrahedral shape of $^{110}$ Zr from covariant density functional theory in 3D lattice space
Fangfang Xu · Bo Li · Zhengxue Ren · Pengwei Zhao
Covariant density functional theory is solved in 3D lattice space by implementing the preconditioned conjugate gradient method with a filtering function (PCG-F). It considerably improves the computational efficiency compared to the previous inverse Hamiltonian method (IHM). This new method is then applied to explore the tetrahedral shape of $^{110}$ Zr in the full deformation space. The ground state of $^{110}$ Zr is found to have a tetrahedral shape, but the deformations $β_{31}$ and $β_{33}$ greatly soften the potential energy surface. This effect is analysed with the microscopic evolution of the single-particle levels near the Fermi surface driven by the deformation.
nucl-thPRC(2024)·23 citations
04
Excluded Volume Effects on Cold Neutron Star Phenomenology
Jesper Leong🇦🇺 · Anthony W. Thomas🇦🇺 · Pierre A. M. Guichon🇫🇷
Observable properties of neutron stars are studied within a hadronic equation of state derived from the quark level. The effect of short-range repulsion is incorporated within the excluded volume framework. It is found that one can sustain neutron stars with masses as large as 2.2 $M_{⊙}$ even including hyperons in $β$ equilibrium, while producing radii and tidal deformabilities consistent with current constraints.
nucl-thastro-ph.HEhep-phNPA(2024)·9 citations
05
Probing the impact of Delta-Baryons on Nuclear Matter and Non-Radial Oscillations in Neutron Stars
Probit Jyoti Kalita🇮🇳 · Pinku Routaray🇮🇳 · Sayantan Ghosh🇮🇳 · Bharat Kumar🇮🇳 · Bijay K. Agrawal🇮🇳
The presence of heavy baryons, such as $Δ$ -baryons and hyperons can significantly impact various properties of Neutron Stars (NSs), like oscillation frequencies, dimensionless tidal deformability, mass, and radii. We explored these effects within the Density-Dependent Relativistic Mean Field formalism. Our analysis considered $Δ$ -admixed NS matter in both hypernuclear and hyperon-free scenarios, providing insights into particle compositions and their effects on NS properties. Our study of non-radial $f$ -mode oscillations revealed a distinct increase in frequency due to the additional baryons. The degree of increase was significantly influenced by the meson-baryon coupling strengths. Notably, the coupling between $Δ$ -resonances and $σ$ -mesons played a highly influential role. In some cases, it led to an approximately 20\% increase in the $f$ -mode oscillation frequency of canonical NSs. These couplings also affect other bulk properties of NSs, including mass, radii, and dimensionless tidal deformability ( $Λ$ ). Comparing our results with available observational data from pulsars (NICER) and gravitational waves (LIGO-VIRGO collaboration), we found strong agreement, particularly concerning $Λ$ .
nucl-thgr-qcJCAP(2024)·7 citations
06
Unified description of superconductivity in neutron stars
Dmitry Kobyakov
In this paper, I study the location and symmetry of superconducting protons. Solving the Tolman-Oppenheimer-Volkoff (TOV) equations based on the unified Barcelona-Catania-Paris-Madrid equation of state (BCPM EoS) and on the pairing gap calculations by Lim and Holt [1], I find that roughly 500 meters of the liquid core (with isotropic and continuous symmetry) and roughly 100-150 meters of the core-crust interface (with anisotropic symmetry) are superconducting, while the rest of the star is normal. To specify whether the superconducting symmetry is discreet in the pasta phase, I study the coexistence of the saturated nuclear and the pure neutron matter using EoS based on the chiral effective field theory (ChEFT). I find that the maximum pressure at coexistence is $P_{*} ≃ 0.5 MeV f m^{- 3}$ . To verify the precision of the coexistence calculations I evaluate the surface and the Coulomb corrections using the compressible liquid drop model. I calculate the proton tunneling rate in the perfectly ordered slab region of the pasta phase and conclude that for the chosen EoS, the proton supercurrent tunneling between the adjacent slabs is negligible and the slab region should be described as a discreet symmetry system of quasi two-dimensional layers.
nucl-thastro-ph.HEcond-mat.supr-conarXiv preprint 2024·1 citation
07
An alternative scheme for pionless EFT: neutron-deuteron scattering in the doublet S-wave
M. Ebert🇩🇪 · H.-W. Hammer🇩🇪 · A. Rusetsky🇩🇪
Using the effective-range expansion for the two-body amplitudes may generate spurious sub-threshold poles outside of the convergence range of the expansion. In the infinite volume, the emergence of such poles leads to the breakdown of unitarity in the three-body amplitude. We discuss the extension of our alternative subtraction scheme for including effective range corrections in pionless effective field theory for spinless bosons to nucleons. In particular, we consider the neutron-deuteron system in the doublet S-wave channel explicitly.
nucl-thhep-latFew Body Syst.(2023)·4 citations
08
Sequential decays of the triple strange process $p ˉ p \to Ω ˉ^{+} Ω^{-} \to K^{+} Λ ˉ K^{-} Λ \to K^{+} p ˉ π^{+} K^{-} p π^{-}$ : a model-independent approach
Deepak Pachattu🇮🇳
A model-independent irreducible tensor formalism is developed to analyse $Ω ˉ Ω$ production in $p ˉ p$ collisions and its subsequent decay via the triple-strange decay process, $Ω ˉ^{+} Ω^{-} \to K^{+} Λ ˉ K^{-} Λ \to K^{+} p ˉ π^{+} K^{-} p π^{-}$ . These processes are relevant for the upcoming experiments at PANDA. We not only provide expressions for the density matrix of the $Ω Ω ˉ$ system but also for the products at each stage of the decay. The Fano statistical tensors so obtained not only completely characterize the relevant final systems but also provide expressions for joint angular distributions. Finally, we show which of the Fano statistical tensors characterizing the $Ω ˉ Ω$ system can be inferred from the Fano statistical tensors characterizing the final $p ˉ p$ system, wherein we also obtain the relation between the production cross sections for $Ω Ω ˉ$ and the final $p p ˉ$ system.
nucl-thhep-phnucl-exNPA(2024)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE