Nuclear Theory·nucl-th

Tuesday·August 25, 2020

8 papers—4 primary·4 cross-listed

01
Coupled-cluster calculations of neutrinoless double-beta decay in $^{48}$ Ca
S. J. Novario🇺🇸 · P. Gysbers🇨🇦 · J. Engel🇺🇸 · G. Hagen🇺🇸 · G. R. Jansen🇺🇸 · T. D. Morris🇺🇸 · P. Navrátil🇨🇦 · T. Papenbrock🇺🇸 · S. Quaglioni🇺🇸
We use coupled-cluster theory and nuclear interactions from chiral effective field theory to compute the nuclear matrix element for the neutrinoless double-beta decay of $^{48}$ Ca. Benchmarks with the no-core shell model in several light nuclei inform us about the accuracy of our approach. For $^{48}$ Ca we find a relatively small matrix element. We also compute the nuclear matrix element for the two-neutrino double-beta decay of $^{48}$ Ca with a quenching factor deduced from two-body currents in recent ab-initio calculation of the Ikeda sum-rule in $^{48}$ Ca [Gysbers et al., Nature Physics 15, 428-431 (2019)].
nucl-thPRL(2021)·115 citations
02
Microscopic model for the collective enhancement of nuclear level densities
Jie Zhao · Tamara Nikšić · Dario Vretenar
A microscopic method for calculating nuclear level densities (NLD) is developed, based on the framework of energy density functionals. Intrinsic level densities are computed from single-quasiparticle spectra obtained in a finite-temperature self-consistent mean-field (SCMF) calculation that takes into account nuclear deformation, and is specified by the choice of the energy density functional (EDF) and pairing interaction. The total level density is calculated by convoluting the intrinsic density with the corresponding collective level density, determined by the eigenstates of a five-dimensional quadrupole or quadrupole plus octupole collective Hamiltonian. The parameters of the Hamiltonian (inertia parameters, collective potential) are consistently determined by deformation-constrained SCMF calculations using the same EDF and pairing interaction. The model is applied in the calculation of NLD of $^{94, 96, 98}$ Mo, $^{106, 108}$ Pd, $^{106, 112}$ Cd, $^{160, 162, 164}$ Dy, $^{166}$ Er, and $^{170, 172}$ Yb, in comparison with available data. It is shown that the collective enhancement of the intrinsic level density, consistently computed from the eigenstates of the corresponding collective Hamiltonian, leads to total NLDs that are in excellent agreement with data over the whole energy range of measured values.
nucl-thnucl-exPRC(2020)·19 citations
03
Local energy-momentum conservation and initial conditions for quark-gluon plasma evolution in nucleus-nucleus collisions at SPS and RHIC BES energies
Antoni Szczurek🇵🇱
We investigate consequences of local energy-momentum conservation for initial eccentricity coefficients in heavy ion collisions at not too high energies relevant for CERN SPS and RHIC BES. Different models of energy density available for pion production are considered. We study dependence of eccentricity coefficients on space-time rapidity for different impact parameters. The naive formula how to define eccentricities breaks with our initial conditions and must be corrected. We predict considerable eccentricities for $ϵ_{1, 2, 3, 4}$ and specific dependence on space-time rapidity as well as on impact parameter for lower energies. The effect becomes smaller at larger energies when restricting to narrow rapidity interval arround zero. Our predictions are in principle input for further hydrodynamical evolution but it is not clear whether they can be easily used. Our initial condition suggest a strong preequilibrium phase which is difficult for modelling.
nucl-thhep-ph0 citations
04
The total reaction cross section of heavy-ion reactions induced by stable and unstable exotic beams: The low-energy regime
L. F. Canto · V. Guimaraes · J. Lubian · M. S. Hussein
In this review paper we present a detailed account of the extraction and the calculation of the total reaction cross section of strongly bound and weakly bound, stable and unstable, exotic, nuclei. We discuss the optical model and the more general coupled channels model of direct reactions. The effect of long-range absorption due to the coupling to excited states in the target and to the breakup continuum in the projectile is also discussed. The generalized optical theorem for charged particle scattering and the resulting sum-of differences method is then discussed. The so-called "quarter-point recipe" is discussed next, and the quarter-point angle is introduced as a simple and rapid mean to obtain the total reaction cross section. The last topic discussed is the reduction of the total reaction cross section that would allow a large body of data to sit on a single universal function. Such a universal function exists in the case of the fusion data, and the aim of this last topic of the review is to extend the fusion case to the total reaction, by adding the direct reaction contribution. Also discussed is the inclusive breakup cross section and how it can be used to extract the total reaction cross section of the interacting fragment with the target. This method is also known as the Surrogate method and represents a case of hybrid reactions. The sum of the integrated inclusive breakup cross section with the complete fusion cross section supplies the total fusion cross section. The main experimental methods to determine the total reaction cross section are also discussed, with emphasis in recent techniques developed to deal with reactions induced by unstable beams.
nucl-thnucl-exEPJA(2020)·47 citations
05
Distribution Amplitudes of Heavy Mesons and Quarkonia on the Light Front
Fernando E. Serna🇧🇷 · Roberto Correa da Silveira🇧🇷 · J. J. Cobos-Martínez🇲🇽 · Bruno El-Bennich🇧🇷 · Eduardo Rojas🇨🇴
The ladder kernel of the Bethe-Salpeter equation is amended by introducing a different flavor dependence of the dressing functions in the heavy-quark sector. Compared with earlier work this allows for the simultaneous calculation of the mass spectrum and leptonic decay constants of light pseudoscalar mesons, the $D_{u}$ , $D_{s}$ , $B_{u}$ , $B_{s}$ and $B_{c}$ mesons and the heavy quarkonia $η_{c}$ and $η_{b}$ within the same framework at a physical pion mass. The corresponding Bethe-Salpeter amplitudes are projected onto the light front and we reconstruct the distribution amplitudes of the mesons in the full theory. A comparison with the first inverse moment of the heavy meson distribution amplitude in heavy quark effective theory is made.
↳ hep-phhep-exhep-latnucl-thEPJC(2020)·45 citations
06
Gravitational wave asteroseismology for low-mass neutron stars
Hajime Sotani
The fundamental ( $f$ -) mode gravitational waves from cold low-mass neutron stars are systematically studied with various equations of state (EOSs) characterized by the nuclear saturation parameters, especially focusing on the phenomena of the avoided crossing with the first pressure ( $p_{1}$ -) mode. We find that the $f$ -mode frequency and the average density for the neutron star at the avoided crossing can be expressed as a function of the parameter, $η$ , which is the specific combination of the nuclear saturation parameters. Owing to these relations, we can derive the empirical formula expressing the $f$ -mode frequency for a low-mass neutron star, whose central density is larger than that for the neutron star at the avoided crossing, as a function of $η$ and the square root of the stellar average density, $x$ . On the other hand, we also derive the empirical formula expressing the $f$ -mode frequency for a neutron star, whose central density is less than that for the neutron star at the avoided crossing, as a function of $x$ independently of the adopted EOS. Furthermore, adopting the empirical formula of $x$ as a function of $η$ and $u_{c}$ , which is the ratio of the stellar central density to the saturation density, we can also rewrite our empirical formula for the $f$ -mode frequency to a function of $η$ and $u_{c}$ . So, by observing the $f$ -mode gravitational wave from a low-mass neutron star, whose mass or gravitational redshift is known, one could evaluate the values of $η$ and $u_{c}$ , which enables us to severely constrain the EOS for neutron star matter.
↳ astro-ph.HEnucl-thPRD(2020)·24 citations
07
Nanoplasmonic Laser Fusion. Response to Földes and Pokol -- Letter to the Editor
László P. Csernai · Norbert Kroó · István Papp · Daniel D. Strottman
Földes and Pokol in their letter "Inertial fusion without compression does not work either with or without nanoplasmonics" criticized our works \cite{CS2015,CKP2018}. Here we refute their argumentation. Our proposed improvement is the combination of two basic research discoveries: (i) The possibility of detonations on space-time hyper-surfaces with time-like normal (i.e. simultaneous detonation in a whole volume) and (ii) to increase the ignition volume to the whole target, by regulating the laser light absorption using nanoantennas. These principles can be realized in an in-line, one dimensional configuration, in the simplest way with two opposing laser beams as in particle colliders \cite{CsEA2020,Bonasera2019}.
↳ physics.plasm-phnucl-thLaser Part.Beams(2020)·0 citations
08
A Study of Multifractal Analysis in 16O-AgBr Collisions at 60A and 200A GeV
Nazeer Ahmad🇮🇳 · Tufail Ahmad🇮🇳 · Omveer Singh🇮🇳 · Shakeel Ahmad🇮🇳
A multifractal analysis to study the multiparticle dynamics in 60A and 200A GeV/c 16O-AgBr collisions has been performed in the pseudorapidity phase space. Multifractal moments Gq as the function of pseudorapidity bin size for different order of the moments, q have been calculated. The power-law behaviour has been observed in the considered data sets. The variation of multifractal dimensions, Dq and multifractal spectral function, f( $α$ q) with order of the moments, q have been studied thoroughly. Dq is found to decrease with increasing order of the moments, q indicating thereby a self-similar behaviour in the multiparticle production in the considered collisions. We have also found a concave downward curve of multifractal spectral function with maxima q=0.
↳ hep-exnucl-exnucl-thJ.Mod.Phys.(2018)·0 citations

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