Nuclear Theory·nucl-th

Thursday·April 8, 2021

9 papers—5 primary·4 cross-listed

01
Thermodynamics of pairing transition for Odd-A nuclei
Tao Yan🇨🇳 · Yanlong Lin🇨🇳 · Lang Liu🇨🇳
The hot nucleus $^{171}$ Yb is investigated by the covariant density functional theory with the PC-PK1 effective interaction. The thermodynamic quantities are evaluated with the canonical ensemble theory. The pairing correlations is treated by the shell-model-like approach, in which the particle numbers are conserved strictly and in which the blocking effect is handled exactly. An S-shaped heat capacity versus temperature of $^{171}$ Yb appears. It has been studied in terms of the blocking effect, the single-particle levels, the pairing gap, and defined seniority components, and compared to the heat capacity of $^{172}$ Yb. The pairing transition from the superfluid state to the normal state can result in the S-shaped heat capacity of $^{172}$ Yb where the one-pair-broken and two-pair-broken states dominate, while the single-particle level structure near the Fermi surface is associated with the S-shaped heat capacity of $^{171}$ Yb. For odd-A nuclei, although the one-pair-broken and two-pair-broken states still contribute, the pairing gap and the pairing transition is relatively weak. The S-shaped heat capacity could be affected due to the blocking of the single-particle level near the Fermi surface.
nucl-thPRC(2021)·8 citations
02
Measurement of Neutron Lifetime and Purcell Effect
Fei He🇨🇳 · Ka-Di Zhu🇨🇳
Purcell effect predicts that spontaneous radiation is not an intrinsic property of matter, but is affected by the environment in which it is located, and is the result of the interaction of matter and field. Purcell effect can be inferred from Fermi Gold rule through strict quantum electrodynamics (QED), and through it can achieve the enhancement or suppression of radiation. We suggest that, in principle, the Purcell effect can be detected at the percentage level of neutron decay in experiments with trapped ultra-cold neutrons. As a test of our claim, we propose a currently achievable experimental protocol that can detect whether Purcell effect has occurred in an trapped ultra-cold neutron lifetime measurement experiment. Finally, we discuss the discrepancy in current methods of measuring neutron lifetime, which may be caused by different experimental setups.
nucl-thhep-phquant-ph1 citation
03
Role of triaxiality in deformed halo nuclei
K. Uzawa🇯🇵 · K. Hagino🇯🇵 · K. Yoshida🇯🇵
It is known that nuclear deformation plays an important role in inducing the halo structure in neutron-rich nuclei by mixing several angular momentum components. While previous theoretical studies on this problem in the literature assume axially symmetric deformation, we here consider non-axially symmetric deformations. With triaxial deformation, the $Ω$ quantum number is admixed in a single-particle wave function, where $Ω$ is the projection of the single-particle angular momentum on the symmetric axis, and the halo structure may arise even when it is absent with the axially symmetric deformation. In this way, the area of halo nuclei may be extended when triaxial deformation is considered. We demonstrate this idea using a deformed Woods-Saxon potential for nuclei with neutron number N=13 and 43.
nucl-thnucl-exPRC(2021)·9 citations
04
Single-nucleon removal cross sections on nucleon and nuclear targets
J.A. Tostevin🇯🇵
The eikonal direct-reaction model, as used in spectroscopic studies of intermediate-energy nucleon-removal reactions on light target nuclei, is considered in the case of a proton target and applied to neutron removal from $^{29}$ Ne at 240 MeV/nucleon. The computed cross sections and their sensitivities are compared using an earlier detailed analysis of carbon target data. The nuclear structure input, for the $^{29}$ Ne ground-state and $^{28}$ Ne final states, is that deduced from the carbon target analysis. The comparisons quantify the sensitivity of the two reactions to the angular momenta and binding energies of the active valence orbitals - showing the carbon target to be relatively more efficient for removals from weakly-bound, low- $ℓ$ , halo-like orbitals. Probing this sensitivity experimentally would provide useful tests of these predictions and of the model's description of the reaction mechanism.
nucl-thnucl-ex3 citations
05
Fermion Pair Dynamics in Open Quantum Systems
S. M. Wang🇺🇸 · W. Nazarewicz🇺🇸
Three-body decay is a rare decay mode observed in a handful of unbound rare isotopes. The angular and energy correlations between emitted nucleons are of particular interest, as they provide invaluable information on the interplay between structure and reaction aspects of the nuclear open quantum system. To study the mechanism of two-nucleon emission, we developed a time-dependent approach that allows us to probe emitted nucleons at long times and large distances. We successfully benchmarked the new method against the Green's function approach and applied it to low-energy two-proton and two-neutron decays. In particular, we studied the interplay between initial-state nucleon-nucleon correlations and final-state interaction. We demonstrated that the time evolution of the two-nucleon wave function is strongly impacted by the diproton/dineutron dynamics and that the correlations between emitted nucleons provide invaluable information on the dinucleon structure in the initial-state.
nucl-thnucl-exPRL(2021)·52 citations
06
Exploring the flavor content of light and heavy-light pseudoscalars
R. M. Moita (Instituto Tecnológico de Aeronáutica, DCTA, São José dos Campos, Brazil)🇧🇷 · J. P. B. C. de Melo (Laboratório de Física Teórica e Computacional - LFTC - UCS/UNICID São Paulo, Brazil)🇧🇷 · K. Tsushima (Laboratório de Física Teórica e Computacional - LFTC - UCS/UNICID- São Paulo, Brazil)🇧🇷 · T. Frederico (Instituto Tecnológico de Aeronáutica, DCTA, São José dos Campos, Brazil)🇧🇷
The electroweak properties of light and charmed D and Ds pseudoscalar mesons are investigated within a unified covariant constituent quark model. The quark-antiquark-meson vertices are assumed to have a symmetric form by the exchange of quark momenta, which is successful in describing the light pseudoscalar meson properties. The flavor decomposition of the elastic electromagnetic form factors, electromagnetic charge radii, and weak decay constants are calculated. Based on the results a discussion on the SU(3) and SU(4) symmetry breaking is made and a comparison with the pion and kaon properties to highlight the Higgs contribution to the structure of these mesons.
↳ hep-phnucl-thPRD(2021)·13 citations
07
Gravo-thermal catastrophe in gravitational collapse and energy progenitor of Gamma-Ray Bursts
She-Sheng Xue🇮🇹
We study the homologous collapse of stellar nuclear core, the virial theorem for hadron collisional relaxations, and photon productions from hadron collisions. We thus show the gravo-thermal dynamical process that transforms gravitational energy to photon energy. The process is energetically and entropically favourable. The total baryon number conservation, Euler equation for energy-momentum conservation and Poisson's equation for gravitational potential are adopted to describe homologous core collapses. The virial theorem determines the hadron collision energy gain from gravitational potential. The hadronic photon production rate determines the photon energy density. The time scales of macroscopic and microscopic processes are studied to verify approximations. As a result, we show the formation of opaque photon-pair spheres, whose total energy, size, temperature and number density, accounting for the main energetic features of Gamma-Ray Burst progenitors. We obtain the intrinsic correlations of these quantities. They depend only on the averaged thermal index of the stellar core. We discuss the possibility to confront them with observational data.
↳ astro-ph.HEnucl-thphysics.plasm-phJCAP(2021)·5 citations
08
Axial-vector nucleon-to-delta transition form factors using the complex-mass renormalization scheme
Y. Ünal🇹🇷 · A. Küçükarslan🇹🇷 · S. Scherer🇩🇪
We investigate the axial-vector nucleon-to-delta transition form factors in the framework of relativistic baryon chiral perturbation theory at the one-loop order using the complex-mass renormalization scheme. We determine the available six free parameters by fitting to an empirical parametrization of the form factors obtained from the BNL neutrino bubble chamber experiments. A unique feature of our calculation is the prediction of a non-vanishing form factor $C_{3}^{A} (Q^{2})$ . Moreover, our results show a surprising sensitivity to the coupling constant $g_{1}$ of the leading-order Lagrangian $L_{π Δ}^{(1)}$ .
↳ hep-phnucl-thPRD(2021)·12 citations
09
Genuine empirical pressure within the proton
Adam Freese🇺🇸 · Gerald A. Miller🇺🇸
A phenomenological extraction of pressure within the proton has recently been performed using JLab CLAS data (arXiv:2104.02031 [nucl-ex]). The extraction used a 3-dimensional Breit frame description in which the initial and final proton states have different momenta. Instead, we obtain the two-dimensional transverse light front pressure densities that incorporate relativistic effects arising from the boosts that cause the initial and final states to differ. The mechanical radius is then determined to be $0.518 \pm 0.06 2_{fit} \pm 0.12 6_{sys} fm$ , which is smaller than the electric charge radius and larger than the light front momentum radius. The forces within the proton are shown to be predominantly repulsive at distances less than $0.43 \pm 0.12 fm$ from the center, and predominantly attractive further out.
↳ hep-phnucl-exnucl-thPRD(2021)·30 citations

Affiliations

first authorsco-authorsvia INSPIRE