Nuclear Theory·nucl-th

Friday·April 19, 2024

7 papers—4 primary·3 cross-listed

01
Systematic shell-model analysis of $2 ν β β$ decay of $^{76}$ Ge and $^{96}$ Zr to the ground and excited states of $^{76}$ Se and $^{96}$ Mo
Deepak Patel · Praveen C. Srivastava · Jouni Suhonen
In this work, we have studied the $2 ν β β$ decay of $^{76}$ Ge and $^{96}$ Zr isotopes utilizing large-scale shell-model calculations. The GWBXG effective interaction has been employed in the calculation of $2 ν β β$ -decay nuclear matrix elements (NMEs). We have tested the effective interaction by comparing the predicted spectroscopic properties, such as energy spectra and transition probabilities, with the available experimental data. The variation of cumulative NMEs with respect to the $1^{+}$ state energies of the intermediate nucleus is also studied, corresponding to $0_{g.s.}^{+} \to 0_{g.s.}^{+}$ , $0_{g.s.}^{+} \to 0_{2}^{+}$ , and $0_{g.s.}^{+} \to 2_{1}^{+}$ transitions between the parent and grand-daughter nuclei. The effective values of axial-vector coupling strength ( $g_{A}^{eff}$ ) are calculated using the predicted NMEs and experimental half-lives for $0_{g.s.}^{+} \to 0_{g.s.}^{+}$ transitions. The extracted half-lives for $0_{g.s.}^{+} \to 0_{2}^{+}$ , and $0_{g.s.}^{+} \to 2_{1}^{+}$ transitions using the shell-model predicted NMEs are consistent with the recent experimental data. The comparison of the shell-model predicted NMEs with previous NMEs available in the literature is discussed. Also, the computed branching ratios for the $2 ν β β$ decay of $^{76}$ Ge and both the $2 ν β β$ and single- $β$ decay of $^{96}$ Zr are reported corresponding to the calculated $g_{A}^{eff}$ values.
nucl-thnucl-exPRC(2024)·5 citations
02
Study of structure of deuteron from analysis of bremsstrahlung emission in proton-deuteron scattering in cluster models
K. A. Shaulskyi (1) · S. P. Maydanyuk (1 and 2) · V. S. Vasilevsky (3) ((1) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine, (2) Wigner Research Centre for Physics, Budapest, Hungary, (3) Bogolyubov Institute for Theoretical Physics, Kyiv, Ukraine)
Purpose: In this paper we investigated emission of bremsstrahlung photons in the scattering of protons off deuterons within the microscopic cluster models in a wide region of the beam energy from low energies up to 1.5 GeV. Methods: Three-cluster model of bremsstrahlung is constructed for such a reaction. Formalism of the model includes form factor of deuteron which characterizes dependence of bremsstrahlung cross sections on structure of deuteron. This gives possibility to investigate the structure of nuclei from analysis of bremsstrahlung cross sections. Results: We studied dependence of the bremsstrahlung cross section on the structure of deuteron. We use three different shapes of the deuteron wave functions. Besides, we also calculate the cross section by neglecting internal structure of deuteron. Analysis of dependence of the cross section on such a parameter shows the following. (1) At beam energies 145 and 195 MeV used in experiments bremsstrahlung cross section is not sensitive visibly on variations of the shape of the deuteron wave functions. (2) Stable difference between cross sections calculated with and without internal structure of deuteron is observed at higher energy of beam (larger 500 MeV). (3) The spectrum is increased as we pass from structureless deuteron (the oscillator length $b = 0$ ) to the deuteron discribed by the shell-model wave function (the realistic oscillator length) inside the full energy region of the emitted photons. Conclusion: Our cluster model is a suitable tool to study the structure of deuteron with high enough precision from bremsstrahlung analysis. We propose new experiments for such an investigation.
nucl-thPRC(2024)·5 citations
03
Single-channel, single-energy partial-wave analysis with continuity improved through minimal phase constraints
A. Svarc🇭🇷 · R.L. Workman🇪🇸
Single-energy partial-wave analysis has often been applied as a way to fit data with minimal model dependence. However, remaining unconstrained, partial waves at neighboring energies will vary discontinuously because the overall amplitude phase cannot be determined through single-channel measurements. This problem can be mitigated through the use of a constraining penalty function based on an associated energy-dependent fit. However, the weight given to this constraint results in a biased fit to the data. In this paper, for the first time, we explore a constraining function which does not influence the fit to data. The constraint comes from the overall phase found in multi-channel fits which, in the present study, are the Bonn-Gatchina and Jülich-Bonn multi-channel analyses. The data are well reproduced and weighting of the penalty function does not influence the result. The method is applied to $K Λ$ photoproduction data and all observables can be maximally well reproduced. While the employed multi-channel analyses display very different multipole amplitudes, we show that the major difference between two sets of multipoles can be related to the different overall phases.
nucl-thPRC(2024)·2 citations
04
Gapless non-hydrodynamic modes in relativistic kinetic theory
Lorenzo Gavassino🇺🇸
We provide rigorous criteria to determine whether the non-hydrodynamic sector of a relativistic kinetic theory is gapless. These general criteria apply to both Boltzmann's equation and approximate models thereof, provided that the latter are consistent with thermodynamic principles. As an application of these criteria, we prove that the non-hydrodynamic sector is gapless whenever the scattering cross-section decays to zero at large energies. Physically, this happens because, if particles with very high energy (compared to the temperature) are free streaming, we can use them to build hot non-hydrodynamic waves, which live longer than any hydrodynamic wave. Since many standard cross-sections in quantum field theory vanish at high energies, the existence of these non-thermal long-lived waves is a rather general feature of relativistic systems.
nucl-thhep-thmath-phmath.MPPRResearch(2024)·26 citations
05
Constraints on the finite volume two-nucleon spectrum at $m_{π} \approx 806$ MeV
William Detmold🇺🇸 · Marc Illa🇺🇸 · William I. Jay🇺🇸 · Assumpta Parreño🇪🇸 · Robert J. Perry🇪🇸 · Phiala E. Shanahan🇺🇸 · Michael L. Wagman🇺🇸
The low-energy finite-volume spectrum of the two-nucleon system at a quark mass corresponding to a pion mass of $m_{π} \approx 806$ MeV is studied with lattice quantum chromodynamics (LQCD) using variational methods. The interpolating-operator sets used in [Phys.Rev.D 107 (2023) 9, 094508] are extended by including a complete basis of local hexaquark operators, as well as plane-wave dibaryon operators built from products of both positive- and negative-parity nucleon operators. Results are presented for the isosinglet and isotriplet two-nucleon channels. In both channels, noticably weaker variational bounds on the lowest few energy eigenvalues are obtained from operator sets which contain only hexaquark operators or operators constructed from the product of two negative-parity nucleons, while other operator sets produce low-energy variational bounds which are consistent within statistical uncertainties. The consequences of these studies for the LQCD understanding of the two-nucleon spectrum are investigated.
↳ hep-lathep-phnucl-thPRD(2025)·21 citations
06
Abnormal solutions of Bethe--Salpeter equation with massless and massive exchanges
Jaume Carbonell1🇫🇷 · Vladimir Karmanov🇷🇺 · Ekaterina Kupriyanova🇷🇺 · Hagop Sazdjian🇫🇷
We summarize the main properties of the so called ''abnormal solutions'' of the Wick--Cutkosky model, i.e. two massive scalar particles interacting via massless scalar exchange ("photons"), within the Bethe--Salpeter equation. These solutions do not exist in the non-relativistic limit, in spite of having very small binding energies. They present a genuine many-body character dominated by photons, with a norm of the valence constituent wave function (two-body norm) that vanishes in the limit of zero binding energy. We present new results concerning the massive-exchange case, in particular determine under which conditions is it possible to obtain such peculiar solutions without spoiling the model by tachyonic states ( $M^{2} < 0$ ).
↳ hep-phcond-mat.str-elnucl-thquant-phFew Body Syst.(2024)·0 citations
07
Dirac Spectral Density in N $_{f}$ =2+1 QCD at T=230 MeV
Andrei Alexandru🇺🇸 · Claudio Bonanno🇪🇸 · Massimo D'Elia🇮🇹 · Ivan Horváth🇺🇸
We compute the renormalized Dirac spectral density in $N_{f} = 2 + 1$ QCD at physical quark masses, temperature $T = 230$ MeV and system size $L_{s} = 3.4$ fm. To that end, we perform a point-wise continuum limit of the staggered density in lattice QCD with staggered quarks. We find, for the first time, that a clear infrared structure (IR peak) emerges in the density of Dirac operator describing dynamical quarks. We also provide numerical evidence that a component of this peak, which becomes dominant in the thermodynamic limit, is due to a non-trivial accumulation of near-zero modes. Features of this structure are consistent with those previously attributed to the recently-proposed IR phase of thermal QCD. Our results (i) provide the only complete first-principles evidence that these IR features exist and are physical; (ii) improve the upper bound for IR-phase transition temperature $T_{IR}$ so that the new window is $200 < T_{IR} < 230$ MeV; (iii) are consistent with non-restoration of anomalous U $_{A}$ (1) symmetry (chiral limit) below $T = 230$ MeV.
↳ hep-lathep-thnucl-thPRD(2024)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE

Systematic shell-model analysis of 2νββ decay of 76Ge and 96Zr to the ground and excited states of 76Se and 96Mo

Study of structure of deuteron from analysis of bremsstrahlung emission in proton-deuteron scattering in cluster models

Single-channel, single-energy partial-wave analysis with continuity improved through minimal phase constraints

Gapless non-hydrodynamic modes in relativistic kinetic theory

Constraints on the finite volume two-nucleon spectrum at mπ​≈806 MeV

Abnormal solutions of Bethe--Salpeter equation with massless and massive exchanges

Dirac Spectral Density in Nf​=2+1 QCD at T=230 MeV

Affiliations

Systematic shell-model analysis of $2 ν β β$ decay of $^{76}$ Ge and $^{96}$ Zr to the ground and excited states of $^{76}$ Se and $^{96}$ Mo

Constraints on the finite volume two-nucleon spectrum at $m_{π} \approx 806$ MeV

Dirac Spectral Density in N $_{f}$ =2+1 QCD at T=230 MeV