Nuclear Theory·nucl-th

Tuesday·January 28, 2020

11 papers—7 primary·4 cross-listed

01
Screening properties of quark-gluon plasma obtained from distribution and correlation functions of the constituent quasiparticle model
V. Filinov🇷🇺 · A. Larkin🇷🇺 · V. Fortov🇷🇺
Based on the constituent quasiparticle model of quark-gluon plasma (QGP), the matrix elements of the density operator and the Wigner function in the color phase space are presented in form of color path integrals over Wiener and SU(3) group Haar measures. Monte Carlo calculations of quark and gluon momentum distributions and spatial pair distribution functions have been carried out for the strongly coupled QGP plasma in thermal equilibrium at zero baryon chemical potential. The Debye screening mass and the running coupling constant have been obtained from the spatial pair distribution function and are in agreement with the available lattice QCD data. At densities related to the average interparticle distance more than 0.4 fm the gluon bound states in the form of glueballs have been found. Comparison with the Maxwell Boltzmann distribution shows significant influence of interparticle interaction on high energy asymptotics of the momentum distribution functions, resulting in appearance of quantum tails. The new color pair correlation function has been introduced, and related new color screening mass has been discussed.
nucl-thhep-phPRC(2020)·0 citations
02
Integrable wave function, describing space-time evolution of alpha-decay
A.Ya.Dzyublik
In the framework of decay theory of Goldberger and Watson we treat $α$ -decay of nuclei as a transition caused by a residual interaction between the initial unperturbed bound state and the scattering states with alpha-particle. The integrable wave function for the $α$ -decay is derived. The alpha-particle is described by the wave packet, having small amplitude inside the nucleus and exponentially growing in external region up to the $α$ -wave front. The Moshinsky's distortions of the alpha-wave front are analyzed. It is found that the energy of the decaying level does not satisfy commonly accepted Bohr-Sommerfeld quantization rule for the quasibound levels. Only far from this condition the decay rate turns out to be determined by the Gamov's factor for the barrier penetrability. The derived general expression for the decay rate is approximated by the familiar quasiclassical formula.
nucl-th3 citations
03
Matter-wave interference originates mass-angle correlation in fusion-fission
Oleksandr Gorbachenko · Sergiy Kun
Mass-angle correlation of fission fragments has been understood as manifestation of quasifission. We show that this is not so: the effect can originate from correlation between fusion-fission amplitudes with different total spins signifying matter-wave interference in compound nucleus processes. This resolves the well-known puzzle with the mass-angle correlation in the complete fusion sub-barrier reaction $^{16}$ O+ $^{238}$ U. Our finding is important for more reliable predictions of production cross sections for superheavy elements. Matter-wave interference also produces quantum-classical transition to the time-orientation localization of the coherently rotating dinucleus in quasifission.
nucl-thquant-ph0 citations
04
Nuclear medium effect on neutron capture reactions during neutron star mergers
Kazuyuki Ogata · Carlos A. Bertulani
The discovery of gravitational waves has confirmed old theoretical predictions that binary systems formed with compact stars play a crucial role not only for cosmology and nuclear astrophysics. As a byproduct of these and subsequent observations, it is now clear that neutron-star mergers can be a competitive site for the production of half of the elements heavier than iron in the universe following a sequence of fast neutron capture reactions known as the r process. In this article we discuss an effect which has been so far neglected in calculations of r-process nucleosynthesis in neutron star mergers. We show that the corrections due to the neutron environment even at relatively small neutron densities, within the bounds of numerical hydrodynamical simulations of neutron star mergers and after the onset of the r process, are non-negligible and need to be taken into account to accurately describe the elemental abundance as determined by observations.
nucl-thJ.Phys.G(2020)·2 citations
05
Correspondence between isoscalar monopole strengths and $α$ inelastic cross sections on $^{24}$ Mg
Kazuyuki Ogata · Yohei Chiba · Yukinori Sakuragi
The correspondence between the isoscalar monopole (IS0) transition strengths and $α$ inelastic cross sections, the $B (IS0)$ - $(α, α^{'})$ correspondence, is investigated for $^{24}$ Mg( $α, α^{'}$ ) at 130 and 386 MeV. We adopt a microscopic coupled-channel reaction framework to link structural inputs, diagonal and transition densities, for $^{24}$ Mg obtained with antisymmetrized molecular dynamics to the ( $α, α^{'}$ ) cross sections. We aim at clarifying how the $B (IS0)$ - $(α, α^{'})$ correspondence is affected by the nuclear distortion, the in-medium modification to the nucleon-nucleon effective interaction in the scattering process, and the coupled-channels effect. It is found that these effects are significant and the explanation of the $B (IS0)$ - $(α, α^{'})$ correspondence in the plane wave limit with the long-wavelength approximation, which is often used, makes no sense. Nevertheless, the $B (IS0)$ - $(α, α^{'})$ correspondence tends to remain because of a strong constraint on the transition densities between the ground state and the $0^{+}$ excited states. The correspondence is found to hold at 386 MeV with an error of about 20%-30%, while it is seriously stained at 130 MeV mainly by the strong nuclear distortion. It is also found that when a $0^{+}$ state that has a different structure from a simple $α$ cluster state is considered, the $B (IS0)$ - $(α, α^{'})$ correspondence becomes less valid. For a quantitative discussion on the $α$ clustering in $0^{+}$ excited states of nuclei, a microscopic description of both the structure and reaction parts will be necessary.
nucl-thPTEP(2021)·2 citations
06
Measuring intensity interference in a low multiplicity system $π π x$ with a new observing method
Q. He🇨🇳 · X. He🇨🇳 · T. Li🇨🇳
Prior proposed observing approaches using event mixing technique for Bose-Einstein correlations (BEC) measurements in exclusive reactions with very low multiplicities are still unsatisfactory due to the problems of sample reduction and introducing extra and unnecessary fitting parameters. We here propose an event mixing method with a new mixing cut, named energy sum range (ESR) cut, to investigate two-pion Bose-Einstein correlations (BEC) in reactions with only two identical pions among three final state particles. This mixing method employs two-pion energy sum characteristic to control the mixing procedures, with no requirement on eliminating any original events. Numerical simulations are performed to show the viability of this new BEC observing method.
nucl-thhep-exnucl-exActa Phys.Polon.B(2020)·0 citations
07
Bulk properties and multi-particle correlations in large and small systems
Bjoern Schenke🇺🇸 · Chun Shen🇺🇸 · Prithwish Tribedy🇺🇸
Charged particle production is calculated in a hybrid framework consisting of the IP-Glasma initial state, MUSIC viscous relativistic fluid dynamics, and the UrQMD microscopic hadronic cascade. Using one set of parameters, we compute observables for a large variety of collision systems. We compare to experimental data in p+p, p+Pb, Xe+Xe, Au+Au and Pb+Pb collisions at various energies, and make predictions for potential O+O runs at RHIC and LHC.
nucl-thhep-phnucl-exNPA(2021)·10 citations
08
Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive $^{222}$ Ra and $^{228}$ Ra Beams
P.A. Butler🇬🇧 · L.P. Gaffney🇬🇧 · P. Spagnoletti🇬🇧 · K. Abrahams🇿🇦 · M. Bowry🇬🇧 · J. Cederkäll🇸🇪 · G. De Angelis🇮🇹 · H. De Witte🇧🇪 · P.E. Garrett🇨🇦 · A. Goldkuhle🇩🇪 · C. Henrich🇩🇪 · A. Illana🇮🇹 and 31 other authors
There is sparse direct experimental evidence that atomic nuclei can exhibit stable pear shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole ( $E 3$ ) matrix elements have been determined for transitions in $^{222, 228}$ Ra nuclei using the method of sub-barrier, multi-step Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of $E$ 3 matrix elements for different nuclear transitions is explained by describing $^{222}$ Ra as pear-shaped with stable octupole deformation, while $^{228}$ Ra behaves like an octupole vibrator.
↳ nucl-exhep-phnucl-thphysics.atom-phPRL(2020)·92 citations
09
Equation of state and composition of the inner crust of an accreting neutron star: multicomponent model
Nikolay N. Shchechilin · Andrey I. Chugunov
Correct interpretation of X-ray observations of transiently accreting neutron stars requires modeling of nuclear-physical processes in these objects. We consider a chain of nuclear reactions that drives the crust composition in an accreting neutron star and heats up the star. We constructed multicomponent approach with the kinetics of nuclear reactions described in simplified stepwise manner. The redistribution of nucleons between nuclei by emission and capture of neutrons is shown to significantly affect the nuclear reaction chains and the composition of the inner crust. In particular, even if the outer crust has one-component composition, the appearance of free neutrons in the inner crust leads to branching of reaction chains and formation of the multicomponent composition. We apply the compressible liquid drop nuclear model, which includes effects of free neutrons on nuclear energies. It allows us to calculate the composition, the heating profile and the equation of state of matter up to densities \rho ~ 2 \times 10^{13} g cm^{-3}.
↳ astro-ph.SRastro-ph.HEnucl-thJ.Phys.Conf.Ser.(2019)·3 citations
10
Superfluidity in Disordered Neutron Stars Crusts
J. A. Sauls🇺🇸 · N. Chamel🇧🇪 · M. A. Alpar🇹🇷
Nonequilibrium conditions imposed by neutrino cooling through the liquid-solid transition lead to disorder in the solid crust of neutron stars. Disorder reduces the superfluid fraction, $ρ_{s} / ρ$ , at densities above that of neutron drip, $ρ_{d} \approx 4 \times 1 0^{11} g / c m^{3}$ . For an amorphous solid crust the suppression of $ρ_{s}$ is small, except in the highest density regions of the crust. In contrast to the strong reduction in neutron conduction predicted for coherent Bragg scattering in a crystalline crust, the disordered solid crust supports sufficient neutron superfluid density to account for pulsar glitches.
↳ astro-ph.HEcond-mat.supr-connucl-th30 citations
11
Centrality criteria of inelastic nucleon-nucleon collisions
Vladimir Komarov🇷🇺 · Bota Baimurzinova🇷🇺 · Ainur Kunsafina🇷🇺 · Dmitry Tsirkov🇷🇺
A process of inelastic nucleon-nucleon collisions with the impact parameter less than a radius of the nucleon quark core is considered. The criteria for selection of such collisions from a full array of the nucleon-nucleon interactions are suggested.
↳ hep-phnucl-exnucl-th1 citation

Affiliations

first authorsco-authorsvia INSPIRE