Nuclear Theory·nucl-th

Tuesday·March 16, 2021

13 papers—6 primary·7 cross-listed

01
Novel Relaxation Time Approximation to the Relativistic Boltzmann Equation
Gabriel S. Rocha🇧🇷 · Gabriel S. Denicol🇧🇷 · Jorge Noronha🇺🇸
We show that the widely used relaxation time approximation to the relativistic Boltzmann equation contains basic flaws, being incompatible with microscopic and macroscopic conservation laws. We propose a new approximation that fixes such fundamental issues and maintains the basic properties of the linearized Boltzmann collision operator. We show how this correction affects transport coefficients, such as the bulk viscosity and particle diffusion.
nucl-thhep-phhep-thPRL(2021)·107 citations
02
Predictive power for superheavy nuclear mass and possible stability beyond the neutron drip line in deformed relativistic Hartree-Bogoliubov theory in continuum
Kaiyuan Zhang🇨🇳 · Xiaotao He🇨🇳 · Jie Meng🇨🇳 · Cong Pan🇨🇳 · Caiwan Shen🇨🇳 · Chen Wang🇨🇳 · Shuangquan Zhang🇨🇳
The predictive power of the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) for nuclear mass is examined in the superheavy region, $102 \leq Z \leq 120$ . The accuracy of predicting the 10 (56) measured (measured and empirical) masses is $0.635$ ( $0.642$ ) MeV, in comparison with $0.515$ ( $1.360$ ) MeV by WS4 and $0.910$ ( $2.831$ ) MeV by FRDM. Possible stability against multineutron emission beyond the two-neutron drip line is explored by the DRHBc theory, which takes into account simultaneously the deformation effects, the pairing correlations, and the continuum effects. Nuclei stable against two- and multineutron emissions beyond the two-neutron drip line are predicted in $_{106}$ Sg, $_{108}$ Hs, $_{110}$ Ds, and $_{112}$ Cn isotopic chains, forming a peninsula of stability adjacent to the nuclear mainland. This stability is mainly due to the deformation which significantly affects the shell structure around the Fermi surface. The pairing correlations and continuum influence the stability peninsula in a self-consistent way.
nucl-thPRC(2021)·63 citations
03
The effect of single-particle space-momentum angle distribution on two-pion HBT correlation in relativistic heavy-ion collisions by using a multiphase transport model
Hang Yang🇨🇳 · Qichun Feng🇨🇳 · Yanyv Ren🇨🇳 · Jingbo Zhang🇨🇳 · Lei Huo🇨🇳
With the string melting version of a multiphase transport(AMPT) model, we analyze the transverse momentum dependence of HBT radius $R_{s}$ and the single-pion transverse angle distribution in central Au+Au collisions at $S_{N N} = 19.6, 27, 39, 62.4, 200$ GeV. And base on a series of functions, a numerical connection between these two phenomena has been built. We can estimate the single-pion transverse angle distribution from the HBT analysis.
nucl-thCPC(2021)·5 citations
04
A polynomial in transverse momentum manifesting thermalisation in nuclear collisions
Rahul Ramachandran Nair🇵🇱
A specific value of light front variable $ζ_{c} (p_{T}, m)$ of the inclusively produced hadrons in a relativistic nuclear collision is constructed as a polynomial in transverse momentum $p_{T}$ of the particle within the UrQMD transport model. It is shown that those particles with the absolute value of their light front variable $ζ$ greater than the corresponding $ζ_{c} (p_{T}, m)$ follow a Fermi-Dirac or Bose-Einstein distribution depending upon the spin of the particle.
nucl-thhep-ph2 citations
05
S-shell $ΛΛ$ hypernuclei based on chiral interactions
Hoai Le🇩🇪 · Johann Haidenbauer🇩🇪 · Ulf-G Meißner🇩🇪 · Andreas Nogga🇩🇪
We generalize the Jacobi no-core shell model (J-NCSM) to study double-strangeness hypernuclei. All particle conversions in the strangeness $S = - 1, - 2$ sectors are explicitly taken into account. In two-body space, such transitions may lead to the coupling between states of identical particles and of non-identical ones. Therefore, a careful consideration is required when determining the combinatorial factors that connect the many-body potential matrix elements and the free-space two-body potentials. Using second quantization, we systematically derive the combinatorial factors in question for $S = 0, - 1, - 2$ sectors. As a first application, we use the J-NCSM to investigate $ΛΛ$ s-shell hypernuclei based on hyperon-hyperon (YY) potentials derived within chiral effective field theory at leading order (LO) and up to next-to-leading order (NLO). We find that the LO potential overbinds $_{ΛΛ}^{6} He$ while the prediction of the NLO interaction is close to experiment. Both interactions also yield a bound state for $_{ΛΛ}^{5} He$ . The $_{ΛΛ}^{4} H$ system is predicted to be unbound.
nucl-thEPJA(2021)·16 citations
06
Analysis of the Pion-Nucleus Scattering within the Folding and the Kisslinger Type Potentials
V.K. Lukyanov🇷🇺 · E.V. Zemlyanaya🇷🇺 · K.V. Lukyanov🇷🇺 · I. Abdul-Magead🇷🇺
Elastic cross sections are calculated and compared with the data on $π^{\pm}$ scattering on $^{28}$ Si, $^{40}$ Ca, $^{58}$ Ni, $^{208}$ Pb nuclei in the energy range from 130 to 290 MeV. To this end, both the folding optical potential (OP) and the local modified Kisslinger-type OP were calculated, and then the $π A$ cross sections were obtained by solving the Klein-Gordon equation to account for the relativization and distortion wave effects. In the folding OPs, the parameters of the elementary $π N$ amplitude were fitted when describing the $π A$ scattering data, and thus the essential in-medium effect on the parameters of the $π N$ amplitude was established since the pion is scattered not on a free but on a bound nuclear nucleon. Fairly good agreement with experimental data was obtained for both models of optical potentials and their forms turn out to be in coincidence in the region of their surfaces.
nucl-thNPA(2021)·4 citations
07
The muon abundance in the primordial Universe
Jan Rafelski🇺🇸 · Cheng Tao Yang🇺🇸
Muon abundance is required for the understanding of several fundamental questions regarding properties of the primordial Universe. In this paper we evaluate the production and decay rates of muons in the cosmic plasma as a function of temperature. This allows us to determine when exactly the muon abundance disappears. When the Universe cools below the temperature $k T_{disappear} \approx 4.135$ MeV the muon decay rate overwhelms production rates and muons vanish quasi-instantaneously from the Universe. Interestingly, we show that at $T_{disappear}$ the muon number is nearly equal to baryon abundance.
↳ hep-phastro-ph.COnucl-thActa Phys.Polon.B(2021)·6 citations
08
Nuclear effects in neutrino-nucleus DIS and probe for short range correlation
Fei Huang🇨🇳 · Ji Xu🇨🇳 · Xing-Hua Yang🇨🇳
We investigate charged-current neutrino-nucleus deep inelastic scattering with particular interests in relationship of short range correlation (SRC) and EMC effect. The structure functions $F_{2}^{A} (x, Q^{2})$ , $x F_{3}^{A} (x, Q^{2})$ and ratios of differential cross sections are presented where the nuclei $A$ are chosen to be carbon, iron and lead. We propose a kind of universal modification functions which would provide a nontrivial test of SRC universality on the platform of neutrino-nucleus scattering and improve our understanding of nucleon structure substantially.
↳ hep-phnucl-thPRD(2021)·8 citations
09
The Pair-Instability Mass Gap for Black Holes
S. E. Woosley (1)🇺🇸 · Alexander Heger (2 and 3 and 4 and 5) ((1) UCSC, (2) Monash, (3) OzGrav, (4) ASTRO-3D, (5) JINA-CEE)🇦🇺
Stellar evolution theory predicts a "gap" in the black hole birth function caused by the pair instability. Presupernova stars that have a core mass below some limiting value, Mlo, after all pulsational activity is finished, collapse to black holes, whereas more massive ones, up to some limiting value, Mhi, explode, promptly and completely, as pair-instability supernovae. Previous work has suggested Mlo is approximately 50 solar masses and Mhi is approximately 130 solar masses. These calculations have been challenged by recent LIGO observations that show many black holes merging with individual masses, Mlo is least some 65 solar masses. Here we explore four factors affecting the theoretical estimates for the boundaries of this mass gap: nuclear reaction rates, evolution in detached binaries, rotation, and hyper-Eddington accretion after black hole birth. Current uncertainties in reaction rates by themselves allow Mlo to rise to 64 solar masses and Mhi as large as 161 solar masses. Rapid rotation could further increase Mlo to about 70 solar masses, depending on the treatment of magnetic torques. Evolution in detached binaries and super-Eddington accretion can, with great uncertainty, increase Mlo still further. Dimensionless Kerr parameters close to unity are allowed for the more massive black holes produced in close binaries, though they are generally smaller.
↳ astro-ph.SRastro-ph.HEgr-qcnucl-thApJL(2021)·266 citations
10
Improving Schrödinger Equation Implementations with Gray Code for Adiabatic Quantum Computers
Chia Cheng Chang🇯🇵 · Kenneth S. McElvain🇺🇸 · Ermal Rrapaj🇺🇸 · Yantao Wu🇯🇵
We reformulate the continuous space Schrödinger equation in terms of spin Hamiltonians. For the kinetic energy operator, the critical concept facilitating the reduction in model complexity is the idea of position encoding. Binary encoding of position produces a Heisenberg-like model and yields exponential improvement in space complexity when compared to classical computing. Encoding with a binary reflected Gray code, and a Hamming distance 2 Gray code yields the additional effect of reducing the spin model down to the XZ and transverse Ising model respectively. We also identify the bijective mapping between diagonal unitaries and the Walsh series, producing the mapping of any real potential to a series of $k$ -local Ising models through the fast Walsh transform. Finally, in a finite volume, we provide some numerical evidence to support the claim that the total time needed for adiabatic evolution is protected by the infrared cutoff of the system. As a result, initial state preparation from a free-field wavefunction to an interacting system is expected to exhibit polynomial time complexity with volume and constant scaling with respect to lattice discretization for all encodings. For the Hamming distance 2 Gray code, the evolution starts with the transverse Hamiltonian before introducing penalties such that the low lying spectrum reproduces the energy levels of the Laplacian. The adiabatic evolution of the penalty Hamiltonian is therefore sensitive to the ultraviolet scale. It is expected to exhibit polynomial time complexity with lattice discretization, or exponential time complexity with respect to the number of qubits given a fixed volume.
↳ quant-phhep-latnucl-thPRX Quantum(2022)·13 citations
11
Strangeness neutral equation of state for QCD with a critical point
J. M. Stafford🇺🇸 · D. Mroczek🇺🇸 · A. R. Nava Acuna🇺🇸 · J. Noronha-Hostler🇺🇸 · P. Parotto🇩🇪 · D. R. P. Price🇺🇸 · C. Ratti🇺🇸
We present a strangeness-neutral equation of state for QCD that exhibits critical behavior and matches lattice QCD results for the Taylor-expanded thermodynamic variables up to fourth-order in $μ_{B} / T$ . It is compatible with the SMASH hadronic transport approach and has a range of temperatures and baryonic chemical potentials relevant for phase II of the Beam Energy Scan at RHIC. We provide an updated version of the software BES-EoS, which produces an equation of state for QCD that includes a critical point in the 3D Ising model universality class. This new version also includes isentropic trejectories and the critical contribution to the correlation length. Since heavy-ion collisions have zero global net-strangeness density and a fixed ratio of electric charge to baryon number, the BES-EoS is more suitable to describe this system. Comparison with the previous version of the EoS is thoroughly discussed.
↳ hep-phnucl-thEur.Phys.J.Plus(2021)·65 citations
12
Single $π^{0}$ Production Off Neutrons Bound in Deuteron with Linearly Polarized Photons
C. Mullen🇬🇧 · S. Gardner🇬🇧 · D. I. Glazier🇬🇧 · S. J. D. Kay🇬🇧 · K. Livingston🇬🇧 · I. I. Strakovsky🇺🇸 · R. L. Workman🇺🇸 · S. Abt🇨🇭 · P. Achenbach🇩🇪 · F. Afzal🇩🇪 · Z. Ahmed🇨🇦 · C. S. Akondi🇺🇸 and 70 other authors
The quasifree $γ d \to π^{0} n (p)$ photon beam asymmetry, $Σ$ , has been measured at photon energies, $E_{γ}$ , from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49 to 148 $^{\circ}$ . In this kinematic region, polarization observables are sensitive to contributions from the $Δ (1232)$ and $N (1440)$ resonances. The extracted values of $Σ$ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID, and Bonn-Gatchina analyses; while a revised SAID fit, including the new $Σ$ measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict $π^{0} n$ photoproduction observables, based on fits to published data in the channels $π^{0} p$ , $π^{+} n$ , and $π^{-} p$ .
↳ nucl-exhep-exhep-phnucl-thEPJA(2021)·6 citations
13
Chiral susceptibility in dense thermo-magnetic QCD medium within HTL approximation
Ritesh Ghosh🇮🇳 · Bithika Karmakar🇮🇳 · Munshi Golam Mustafa🇮🇳
We have computed the chiral susceptibility in quark-gluon plasma in presence of finite chemical potential and weak magnetic field within hard thermal loop approximation. First we construct the massive effective quark propagator in a thermomagnetic medium. Then we obtain completely analytic expression for the chiral susceptibility in weak magnetic field approximation. In the absence of magnetic field the thermal chiral susceptibility increases in presence of finite chemical potential. The effect of thermomagnetic correction is found to be very marginal as temperature is the dominant scale in weak field approximation.
↳ hep-phhep-latnucl-thPRD(2021)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE