Nuclear Theory·nucl-th

Tuesday·September 10, 2024

21 papers—6 primary·15 cross-listed

01
[Submitted on 6 Sept 2024]
Weak decays in superheavy nuclei
A. Ravlić · W. Nazarewicz
Superheavy nuclei represent the heaviest atoms and nuclides known at the limit of mass and charge. The observed superheavy nuclei are all proton-rich; they decay primarily by emitting $α$ particles and fission, with a possible small electron capture (EC) branch. Due to the huge atomic numbers and associated relativistic effects, EC-decays of superheavy systems are expected to differ from what is known in lighter nuclei. In this paper, using the quantified relativistic nuclear density functional theory and the quasiparticle random-phase approximation with the interaction optimized to experimental $β^{-}$ -decay half-lives and Gamow-Teller resonance energies, we study the EC/ $β^{\pm}$ -decays in $Z = 101 - 118$ nuclei. Both allowed ( $1^{+}$ ) and first-forbidden ( $0^{-}, 1^{-}$ and $2^{-}$ ) transitions are considered. We show that the first-forbidden $1^{-}$ transitions dominate the decay rates in almost all studied nuclei. For proton-rich nuclei, EC dominates over $β^{+}$ decay. We identify 44 nuclei with EC/ $β^{+}$ branching ratio larger than 5\%, indicating a possible competition with $α$ -decay and spontaneous fission channels.
Comments:
7 pages, 4 figures, submitted for publication
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2409.04620 [pdf]
PRC(2025)·7 citations
02
[Submitted on 7 Sept 2024]
Effect of vector meson spin coherence on the measurements of chiral magnetic effect in heavy-ion collisions
Zhiyi Wang🇨🇳 · Jinhui Chen🇨🇳 · Diyu Shen🇨🇳 · Aihong Tang🇺🇸 · Gang Wang🇺🇸
The chiral magnetic effect (CME) in heavy-ion collisions reflects the local violation of $P$ and $C P$ symmetries in strong interactions and manifests as electric charge separation along the direction of the magnetic field created by the wounded nuclei. The experimental observables for the CME, such as the $γ_{112}$ correlator, the $R_{Ψ_{2}} (Δ S)$ correlator, and the signed balance functions, however, are also subject to non-CME backgrounds, including those from resonance decays. A previous study showed that the CME observables are affected by the diagonal component of the spin density matrix, the $ρ_{00}$ for vector mesons. In this work, we study the contributions from the other elements of the spin density matrix using a toy model and a multiphase transport model. We find that the real part of the $ρ_{1 - 1}$ component, $Re ρ_{1 - 1}$ , affects the CME observables in a manner opposite to that of the $ρ_{00}$ . All three aforementioned CME observables show a linear dependence on $Re ρ_{1 - 1}$ in the model calculations, supporting our analytical derivations. The rest elements of the spin density matrix do not contribute to the CME observables. The off-diagonal terms in the spin density matrix indicate spin coherence and may be nonzero in heavy-ion collisions due to local spin polarization or spin-spin correlations. Thus, $Re ρ_{1 - 1}$ , along with $ρ_{00}$ , could play a significant role in interpreting measurements in search of the CME.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2409.04675 [pdf]
PRC(2025)·5 citations
03
[Submitted on 7 Sept 2024]
Partial-wave analysis to determine the spin of $Ξ (1690)^{-}$ and $Ξ (1820)^{-}$ produced in $p p$ annihilation
Deepak Pachattu🇮🇳
Recently [arXiv:2201.03852v2] the PANDA collaboration studied the feasibility of determining the spin and parity of the $Ξ (1690)^{-}$ and $Ξ (1820)^{-}$ resonances in the $Λ K^{-}$ system produced in $p ˉ p$ collisions via the reaction channel $p p \to Ξ ˉ^{+} Λ K^{-}$ . This contribution aims to study these reactions using a model-independent irreducible tensor formalism developed earlier. This study leads us to identify the partial-wave amplitude, which would be zero if $Ξ (1690)^{-}$ or $Ξ (1820)^{-}$ had spin-1/2, provided these resonances are produced at threshold (s-wave production).
Comments:
7 pages, uses RevTeX, no figures or tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex)
arXiv:
2409.04886 [pdf]
EPJA(2025)·0 citations
04
[Submitted on 8 Sept 2024]
Nuclear transparency and shadowing of the two-step process in the $A (e, e^{'} π^{+})$ reaction
Tae Keun Choi🇰🇷 · Kook-Jin Kong🇰🇷 · Byung-Geel Yu🇰🇷
We investigate nuclear transparency induced by pion electroproduction on nuclei, $A (e, e^{'} π^{+})$ , with our interest in the role of the two-step process in the Glauber multiple scattering theory. Based on the framework in which the quantum diffusion model is incorporated into the Glauber theory, the experimental data in the range of photon virtuality $0.5 < Q^{2} < 10$ GeV $^{2} / c^{2}$ are analyzed, including the recent JLab data at the 6 GeV electron beam together with the proposal for the 12 GeV upgrade. Application of the quantum diffusion model during the formation length of the quark/antiquark $(q q ˉ)$ structure of a pion reproduces the increase in the nuclear transparency up to high $Q^{2}$ , showing evidence of color transparency. In contrast, through the coherent length of the $γ^{*}$ fluctuation into $ρ^{0}$ , the two-step process with the $ρN$ scattering cross section chosen to be $σ_{ρN} = σ_{π N}$ contributes to a reduction of the nuclear transparency in the whole range of $Q^{2}$ . Combined with the one-step process (direct photon coupling) usually adopted in the original formulation of the Glauber theory, this reaction mechanism provides another source of the $Q^{2}$ dependence of the transparency at low virtualities through the shadowing in the initial state interaction. By the further absorption due to the shadowing, a better agreement is obtained with the pion transparency measured in the $A (e, e^{'} π^{+})$ reaction for $^{12}$ C, $^{27}$ Al, $^{63}$ Cu, and $^{197}$ Au nuclei. A discussion of the $Q^{2}$ dependence of the parameter $α$ for the transparency $T_{A} = A^{α - 1}$ is given.
Comments:
7 pages, 4 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2409.05129 [pdf]
PRC(2025)·4 citations
05
[Submitted on 9 Sept 2024]
Emergent chirality and superfluidity of parity-doubled baryons in neutron stars
Shigehiro Yasui🇯🇵 · Muneto Nitta🇯🇵 · Chihiro Sasaki🇯🇵
We propose novel superfluids induced by the parity-doubled baryons. The parity-doubled baryons, i.e., a nucleon $N (940)$ with spin-parity $J^{P} = 1/ 2^{+}$ and an excited nucleon $N^{*} (1535)$ with $J^{P} = 1/ 2^{-}$ in vacuum, become degenerate at sufficiently high density where the chiral symmetry is restored. In this study, we extend the conventional $U (1)$ chiral symmetry to the higher dimensional symmetries, dubbed emergent chiral symmetries, including the naive and mirror assignments as their subgroups. Starting with the Lagrangian up to four-point interactions among the neutron $n$ and its chiral partner $n^{*}$ , neutral components in $N$ and $N^{*}$ , in pure neutron matter, we investigate the properties of the ground state with a pairing gap generated by the $n$ and $n^{*}$ in the mean-field approximation. We find vector-type condensates that induce the dynamical breaking of a new class of internal symmetries, emergent chiral symmetries, as well as the baryon number and the rotational symmetries of the real space, indicating the appearance of massless Nambu-Goldstone bosons consisting of six quarks: emergent pions, superfluid phonons, and magnons, respectively. We also study the fermionic excitation modes at low-energy scales, and show that they exhibit a spatial anisotropy of the propagation at the Dirac cone in momentum space. Some phenomenological implications are advocated, shedding new light on the properties of neutron stars.
Comments:
23 pages, 5 figures, 4 tables
Subjects:
Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2409.05670 [pdf]
PRD(2025)·5 citations
06
[Submitted on 9 Sept 2024]
A simple explanation of the absence of the spherical nuclei with the hidden-color states
Tao Wang🇨🇳
Inspired by the EMC effect, the Cd puzzle and the SU3-IBM, a hypothesis can be given for a nucleus, that only the nucleus itself is a trivial (0,0) representation of the SU(3) group, which leads to the simple conclusion that spherical nucleus does not exist and the spherical mean field is not allowed. The key conclusion is that the whole nucleus should have many hidden-color states, and the quark-gluon degrees of freedom are required even at the low-energy excitation of the nucleus.
Comments:
For the first time, the clear evidence for the existence of the color degree of freedom of the nucleons in the nucleus is given. Comments are welcome
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2409.05723 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Weak decays in superheavy nuclei

Effect of vector meson spin coherence on the measurements of chiral magnetic effect in heavy-ion collisions

Partial-wave analysis to determine the spin of Ξ(1690)− and Ξ(1820)− produced in p​p annihilation

Nuclear transparency and shadowing of the two-step process in the A(e,e′π+) reaction

Emergent chirality and superfluidity of parity-doubled baryons in neutron stars

A simple explanation of the absence of the spherical nuclei with the hidden-color states

Affiliations

Partial-wave analysis to determine the spin of $Ξ (1690)^{-}$ and $Ξ (1820)^{-}$ produced in $p p$ annihilation

Nuclear transparency and shadowing of the two-step process in the $A (e, e^{'} π^{+})$ reaction