Nuclear Theory·nucl-th

Thursday·October 15, 2020

9 papers—3 primary·6 cross-listed

01
Fission Dynamics of Compound Nuclei: Pairing versus Fluctuations
Yu Qiang · Junchen Pei · Paul Stevenson
Energy dependence of fission observables is a key issue for wide nuclear applications. We studied real-time fission dynamics from low-energy to high excitations in the compound nucleus $^{240}$ Pu with the time-dependent Hartree-Fock+BCS approach. It is shown that the evolution time of the later phase of fission towards scission is considerably lengthened at finite temperature. As the role of dynamical pairing is vanishing at high excitations, the random transition between single-particle levels around the Fermi surface to mimic thermal fluctuations is indispensable to drive fission. The obtained fission yields and total kinetic energies with fluctuations can be divided into two asymmetric scission channels, namely S1 and S2, which explain well experimental results, and give microscopic support to the Brosa model. With increasing fluctuations, S2 channel takes over S1 channel and the spreading fission observables are obtained.
nucl-thPRC(2021)·35 citations
02
$Λ_{c} N$ interaction in leading order covariant chiral effective field theory
Jing Song🇨🇳 · Yang Xiao🇨🇳 · Zhi-Wei Liu🇨🇳 · Chun-Xuan Wang🇨🇳 · Kai-Wen Li🇨🇳 · Li-Sheng Geng🇨🇳
We study the $Λ_{c} N$ interaction in the covariant chiral effective field theory (ChEFT) at leading order. All the relevant low-energy constants are determined by fitting to the lattice QCD simulations from the HAL QCD Collaboration. Extrapolating the results to the physical point, we show that the $Λ_{c} N$ interaction is weakly attractive in the $^{1} S_{0}$ channel, but in the $^{3} S_{1}$ channel, it is only attractive at extremely low energies and soon turns repulsive for larger laboratory energy. Furthermore, we show that the neglect of the $^{3} S_{1} -^{3} D_{1}$ coupling provided by the leading order covariant ChEFT would result in an attractive interaction in the $^{3} S_{1}$ channel at the physical point, which coincides with the previous non-relatistic ChEFT study. As a byproduct, we predict the $^{3} D_{1}$ phase shifts and the mixing angel $ε_{1}$ , which can be checked by future lattice QCD simulations. In addition, we compare the $Λ_{c} N$ interaction with the $Λ N$ and $N N$ interactions to study how the baryon-nucleon ( $B N$ ) interactions evolve as a function of the baryon mass with the replacement of a light quark by a strange or charm quark in the baryon ( $B$ ).
nucl-thhep-phPRC(2020)·16 citations
03
Hadrons and Few-Body Physics
Jean-Marc Richard🇫🇷
We present a selection of topics with an interplay of hadron and few-body physics. This includes few-nucleon systems, light hypernuclei and quark dynamics for baryons and multiquarks. It is stressed that standard quark models predict very few stable multiquarks.
nucl-thhep-phFew Body Syst.(2020)·3 citations
04
Mass structure of hadrons and light-front sum rules in t' Hooft model
Xiangdong Ji🇺🇸 · Yizhuang Liu🇨🇳 · Ismail Zahed🇺🇸
We study the mass/energy structure of the bound state of hadrons in two-dimensional quantum chromodynamics in the large number of color limit (t' Hooft model). We analyze separately the contributions from the traceless and trace part of the energy-momentum tensor, and show that the masses are related to the matrix elements of the scalar charge and Coulomb energy. We derive the light-front sum rules for the scalar charge and Coulomb energy, expressed in terms of the light-front wave functions, and find that they are regular at $x = 0$ without the delta function contribution. We also consider the result for the massless Goldstone boson, as well as the structure of the gravitational form factors of the bound meson states.
↳ hep-phhep-lathep-thnucl-thPRD(2021)·23 citations
05
Hybrid Stars with Hyperons and Strange Quark Matter
Wasif Husain🇦🇺 · Anthony W. Thomas🇦🇺
We consider the possibility of having hybrid stars with a phase transition from hadrons into strange matter at the core of a neutron star in b equilibrium. For the hadron phase equation of state (EoS) the quark-meson coupling model is used, while the MIT bag model is used to describe the strange matter phase. The phase transition is treated using the Gibbs construction method and results are calculated and checked against the observational constaints imposed on the EoS. The results are also compared with the hadronic EoS including hyperons, F-QMC700
↳ hep-phastro-ph.HEnucl-thAIP Conf.Proc.(2021)·11 citations
06
Hyperfine structure of the first rotational level in H $_{2}$ , D $_{2}$ and HD molecules and the deuteron quadrupole moment
Mariusz Puchalski · Jacek Komasa · Krzysztof Pachucki
We perform the four-body calculation of the hyperfine structure in the first rotational state $J = 1$ of the H $_{2}$ , D $_{2}$ , and HD molecules and determine the accurate value for the deuteron electric quadrupole moment $Q_{d} = 0.285 699 (15) (18)$ fm $^{2}$ in significant disagreement with former spectroscopic determinations. Our results for the hyperfine parameters agree very well with the currently most accurate molecular-beam magnetic resonance measurement performed several decades ago by N.F. Ramsey and coworkers. They also indicate the significance of previously neglected nonadiabatic effects. Moreover, a very good agreement with the recent calculation of $Q_{d}$ based on the chiral effective field theory, although much less accurate, indicates the importance of the spin dependence of nucleon interactions in the accurate description of nuclei.
↳ physics.chem-phnucl-thPRL(2020)·17 citations
07
Resonance photoproduction of pionic atoms at the Gamma Factory
Victor V. Flambaum🇦🇺 · Junlan Jin🇨🇳 · Dmitry Budker🇩🇪
We present a possibility of direct resonance production of pionic atoms (Coulomb bound states of a negative pion and a nucleus) with a rate of up to $\sim 1 0^{10}$ per second using the gamma-ray beams from the Gamma Factory.
↳ nucl-exnucl-thphysics.atom-phPRC(2021)·13 citations
08
Ab initio construction of the energy density functional for electron systems with the functional-renormalization-group-aided density functional theory
Takeru Yokota🇯🇵 · Tomoya Naito🇯🇵
We show an $ab initio$ construction of the energy density functional (EDF) for electron systems using the functional renormalization group. The correlation energies of the homogeneous electron gas given in our framework reproduce the exact behavior at high density and agree with the Monte-Carlo data in a wide range of densities. Our analytic technique enables us to get the correlation energies efficiently for various densities, which realizes the determination of EDF in the local density approximation (LDA) without any fitting for physically relevant densities. Applied to the Kohn-Sham calculation for the noble gas atoms, our EDF shows comparable results to those of other conventional ones in LDA.
↳ cond-mat.str-elcond-mat.quant-gashep-thnucl-th+1PRResearch(2021)·17 citations
09
Standard Model $O (α)$ renormalization of $g_{A}$ and its impact on new physics searches
Leendert Hayen🇺🇸
We present an $O (α)$ Standard Model calculation of the inner radiative corrections to Gamow-Teller $β$ decays. We find that \textit{a priori} contributions arise from the photonic vertex correction and $γ W$ box diagram. Upon evaluation most elastic contributions vanish due to crossing symmetry or cancellation between isoscalar and isovector photonic contributions, leaving only the polarized parity-odd contribution, i.e., the Gamow-Teller equivalent of the well-known axial $γ W$ box contribution for Fermi decays. We show that weak magnetism contributes significantly to the Born amplitude, and consider additional hadronic contributions at low energy using a holomorphic continuation of the polarized Bjorken sum rule constrained by experimental data. We perform the same procedure for the Fermi inner radiative correction through a combination of the running of Bjorken and Gross-Llewellyn Smith sum rules. We discuss heavy flavor, higher-twist, and target mass corrections and find a significant increase at low momentum from the latter. We find $Δ_{R}^{A} = 0.02532 (22)$ and $Δ_{R}^{V} = 0.02473 (27)$ for axial and vector inner radiative corrections, respectively, resulting in $Δ_{R}^{A} - Δ_{R}^{V} = 0.60 (5) \times 1 0^{- 3}$ , which allows us to extract $g_{A}^{0}$ for the first time to our knowledge. We discuss consequences for comparing experimental data to lattice calculations in beyond Standard Model fits. Further, we show how some traditional $β$ decay calculations contain part of this effect but fail to account for cancellations in the full $O (α)$ result. Finally, we correct for a double-counting instance in the isospin $T = 1/2$ mirror decay extraction of $∣ V_{u d} ∣$ , the up-down matrix element of the Cabibbo-Kobayashi-Maskawa matrix, resolving a long-standing tension and leading to increased precision.
↳ hep-phhep-latnucl-exnucl-thPRD(2021)·113 citations

Affiliations

first authorsco-authorsvia INSPIRE