Nuclear Theory·nucl-th

Wednesday·June 5, 2019

7 papers—5 primary·2 cross-listed

01
[Submitted on 3 Jun 2019]
Adiabatic projection method with Euclidean time subspace projection
Serdar Elhatisari🇹🇷
Euclidean time projection is a powerful tool that uses exponential decay to extract the low-energy information of quantum systems. The adiabatic projection method, which is based on Euclidean time projection, is a procedure for studying scattering and reactions on the lattice. The method constructs the adiabatic Hamiltonian that gives the low-lying energies and wave functions of two-cluster systems. In this paper we seek the answer to the question whether an adiabatic Hamiltonian constructed in a smaller subspace of the two-cluster state space can still provide information on the low-lying spectrum and the corresponding wave functions. We present the results from our investigations on constructing the adiabatic Hamiltonian using Euclidean time projection and extracting details of the low-energy spectrum and wave functions by diagonalizing it. In our analyses we consider systems of fermion-fermion and fermion-dimer interacting via a zero-range attractive potential in one dimension, and fermion-fermion interacting via an attractive Gaussian potential in three dimensions. The results presented here provide a guide for improving the adiabatic projection method and for reducing the computational costs of large-scale calculations of \emph{ab initio} nuclear scattering and reactions using Monte Carlo methods.
Comments:
13 pages, 5 figures, version accepted for publication in EJPA
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
arXiv:
1906.01046 [pdf]
EPJA(2019)·7 citations
02
[Submitted on 4 Jun 2019]
Analytical forms of wave function and form factors of deuteron
V.I. Zhaba🇺🇦
On the received coefficients of the analytical forms for deuteron wave function in coordinate representation in form r^(l+1)*exp(-A*r) for the modern realistic nucleon-nucleon potentials NijmI, NijmII, Nijm93, Reid93 and Argonne v18 are calculated charge GC(p), quadrupole GQ(p) and magnetic GM(p) deuteron form factors. An original dipole fit for proton and neutron isoscalar electric and magnetic form factors is used for calculations. Theoretical calculations of values of the deuteron form factor are compared with their experimental data of world collaborations (Bates, BLAST, Bonn, JLab, Mainz, Naval Research Lab, NIKHEF, Orsay, Saclay, SLAC, Stanford, VEPP3 and VEPP4) and reviews (Abbott, Boden, Garcon and Karpius). The change of the sign of form factors is in the pulse regions at 4.7-4.9 fm-1 for GC; at 12.8-14.7 fm-1 for GQ; at 6.3-8.1 and 11.4-12.2 fm-1 for GM. The theoretical values for the form factors GQ(0) and GM(0) were calculated at the boundary condition for the momentum at p2=0. Calculated positions of the zero for deuteron form factors are compared with values for other potential models. The peculiarities of parametrizations of deuteron form factors for theoretical approaches and fits of theoretical calculations to experimental values, which are described in the cited literature, are analyzed. Formulas for spherical and quadrupole form factors are writed, which are expressed in terms of the coefficients for the indicated deuteron wave function. At large values of momentum the asymptotics of the deuteron form factors are determined by the coefficients of the analytical forms for deuteron wave function, nucleon isoscalar form factors and the order of momentum in the denominator. The further use of deuteron form factors for obtaining polarization observables in processes involving deuteron as a projectile is discussed.
Comments:
12 pages, in Ukrainian, 3 figures, 4 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1906.01389 [pdf]
Visnyk Lviv University.Series Physics(2019)·3 citations
03
[Submitted on 4 Jun 2019]
"Splitting" magnetic catalysis effect prevents vacuum superconductivity in strong magnetic fields
Gaoqing Cao🇨🇳
By comparing the two- and three-flavor Nambu--Jona-Lasinio (NJL) models, we demonstrate that the naively expected vacuum superconductivity (VSC) in constant magnetic field $B = B z^$ is disfavored due to the splitting magnetic catalysis effect (MCE) to chiral condensates with different quark flavors. Based on the simple two-flavor NJL model, we illuminate, in the lowest Landau level approximation, the similar origins of $π^{0}$ and $ρ ˉ_{1}^{+}$ ( $ρ^{+}$ meson with spin $S_{z} = 1$ ) mass reductions with smaller $B$ and their different features at larger $B$ . With the full Landau levels, the two-flavor NJL model is found to be invalid to study the magnetic field effect to $ρ ˉ_{1}^{+}$ meson with physical vacuum mass $775 MeV$ . Then, restricted to $ρ$ meson mass below two-quark threshold in vacuum, that is $m_{ρ}^{v} < 2 m_{q}^{v}$ , it is found that $π^{0}$ mass decreases and then increases with $B$ slowly, and $ρ ˉ_{1}^{+}$ mass vanishing point is delayed to larger $B$ compared to the point particle result. In the more realistic three-flavor NJL model, all the quark masses split in strong magnetic field as a combinatorial result of their different current masses and electric charges. By choosing a vacuum mass closer to the physical one, $ρ ˉ_{1}^{+}$ meson mass is found to be consistent with the LQCD results semi-quantitatively in smaller $B$ region but increase in larger $B$ region. These features are mainly outcomes of the interplay between the $S_{z} - B$ coupling effect and splitting MCE to the composite $u$ and $d$ quarks, which definitely disfavors VSC when the latter dominates. Furthermore, mesonic flavor mixing is modified by $B$ among the neutral pseudoscalars: $π^{0}, η_{0}$ and $η_{8}$ , which is very important to suppress the mass enhancement of the effective mass eigenstates at large $B$ .
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1906.01398 [pdf]
PRD(2019)·23 citations
04
[Submitted on 1 Jun 2019]
Influence of initial-state momentum anisotropy on the final-state collectivity in small collision systems
Maowu Nie🇨🇳 · Li Yi🇨🇳 · Jiangyong Jia🇨🇳 · Guoliang Ma🇺🇸
A multi-phase transport model is used to understand the origin of long-range collective azimuthal correlations in small-system collisions. To disentangle between collectivity associated with initial-state intrinsic momentum anisotropy and the collectivity arising as a final-state response to the collision geometry, we studied the development of collectivity in 5.02 TeV $p$ +Pb collisions with both initial-state and final-state effects included. We find that the initial momentum anisotropy may not be fully isotropized through parton interactions, and the final-state partonic collectivity in general are correlated with both the initial momentum anisotropy and the shape of the collision geometry. The initial momentum anisotropy also influences the event by event fluctuation of collective flow. Therefore the mere evidence of geometry response of the collective flow can not rule out the presence of large contributions from the initial state.
Comments:
5 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1906.01422 [pdf]
PRC(2019)·18 citations
05
[Submitted on 4 Jun 2019]
Diffusion of charm quarks in jets in high-energy heavy-ion collisions
Sa Wang🇨🇳 · Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
The radial distribution of $D^{0}$ mesons in jets probes the diffusion of charm quark relative to the jet axis and provides a new perspective to study the interaction mechanisms between heavy quarks and the medium in the nucleus-nucleus collisions. The in-medium parton propagations are described by a Monte Carlo transport model which uses the next-to-leading order (NLO) plus parton shower (PS) event generator SHERPA as input and includes elastic (collisional) and inelastic (radiative) interaction for heavy quarks as well as light partons. At low $D^{0}$ meson $p_{T}$ , the radial distribution significantly shifts to larger radius indicating a strong diffusion effect which is consistent with the recent experimental data. We demonstrate that the angular deviation of charm quarks declines with $p_{T}$ and is very sensitive to the collisional more than radiative interaction at $p_{T} < 5$ ~GeV. As predictions, we present the $D^{0}$ meson radial distribution in jets in p+p and $0 - 10%$ Au+Au collisions at $s_{N N} = 200$ ~GeV at the RHIC, and also estimate the nuclear modification factor of charm jet in central Au+Au collisions at 200~GeV at the RHIC and central Pb+Pb collisions at $5.02$ ~TeV at the LHC.
Comments:
8 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
1906.01499 [pdf]
EPJC(2019)·39 citations
06
[Submitted on 22 May 2019] (cross-list from cond-mat.stat-mech)
Kramers's escape rate problem within a non-Markovian description
Benjamin Schüller🇩🇪 · Alex Meistrenko🇩🇪 · Hendrik van Hees🇩🇪 · Zhe Xu🇨🇳 · Carsten Greiner🇩🇪
We compare the thermal escape rates of a Brownian particle, initially trapped into one of the two wells of an asymmetric double-well potential, for thermal Markovian and non-Markovian noise. The Markovian treatment of this problem goes originally back to the studies of Kramers in 1940 and is therefore often referred to as "Kramers's escape rate problem". We solve the generalized Langevin equation for the trajectories of the particles numerically and analytically for both limiting cases, Markovian and non-Markovian thermal noise. We compute the escape rate and work out the fundamental differences arising from finite correlation times of the thermal noise.
Comments:
42 pages, 18 figures
Subjects:
Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1905.09652 [pdf]
Annals Phys.(2020)·7 citations
07
[Submitted on 4 Jun 2019] (cross-list from nucl-ex)
Effects of one valence proton on seniority and angular momentum of neutrons in neutron-rich $^{122 - 131}$ Sb $_{51}$ isotopes
S. Biswas🇫🇷 · A. Lemasson🇫🇷 · M. Rejmund🇫🇷 · A. Navin🇫🇷 · Y.H. Kim🇫🇷 · C. Michelagnoli🇫🇷 · I. Stefan🇫🇷 · R. Banik🇮🇳 · P. Bednarczyk🇵🇱 · S. Bhattacharya🇮🇳 · S. Bhattacharyya🇮🇳 · E. Clément🇫🇷 and 49 other authors
The neutron-rich $^{122 - 131}$ Sb isotopes were produced as fission fragments in the reaction $^{9}$ Be( $^{238}$ U,~f) with 6.2 MeV/u beam energy. An unique setup, consisting of AGATA, VAMOS++ and EXOGAM detectors, was used which enabled the prompt-delayed gamma-ray ( $γ$ ) spectroscopy of fission fragments in the time range of 100 ns - 200 $μ$ s. New isomers, prompt and delayed transitions were established in the even-A $^{122 - 130}$ Sb isotopes. In the odd-A $^{123 - 131}$ Sb isotopes, new prompt and delayed $γ$ -ray transitions were identified, in addition to the confirmation of the previously known isomers. The half-lives of the isomeric states and the $B (E 2)$ transition probabilities of the observed transitions depopulating these isomers were extracted. The experimental data was compared with the theoretical results obtained in the framework of Large-Scale Shell-Model (LSSM) calculations in a restricted model space. Modifications of several components of the shell model interaction were introduced to obtain a consistent agreement with the excitation energies and the $B (E 2)$ transition probabilities in neutron-rich Sn and Sb isotopes. The isomeric configurations in Sn and Sb were found to be relatively pure. Further, the calculations revealed that the presence of a single valence proton, mainly in the $g_{7/2}$ orbital in Sb isotopes, leads to significant mixing (due to the $ν π$ interaction) of: (i) the neutron seniorities ( $υ_{ν}$ ) and (ii) the neutron angular momentum ( $I_{ν}$ ). The above features have a weak impact on the excitation energies, but have an important impact on the $B (E 2)$ transition probabilities. In addition, a constancy of the relative excitation energies irrespective of neutron seniority and neutron number in Sn and Sb was observed.
Comments:
23 pages, 18 figures, 10 tables
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1906.01245 [pdf]
PRC(2019)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE

Adiabatic projection method with Euclidean time subspace projection

Analytical forms of wave function and form factors of deuteron

"Splitting" magnetic catalysis effect prevents vacuum superconductivity in strong magnetic fields

Influence of initial-state momentum anisotropy on the final-state collectivity in small collision systems

Diffusion of charm quarks in jets in high-energy heavy-ion collisions

Kramers's escape rate problem within a non-Markovian description

Effects of one valence proton on seniority and angular momentum of neutrons in neutron-rich 122−131Sb51​ isotopes

Affiliations

Effects of one valence proton on seniority and angular momentum of neutrons in neutron-rich $^{122 - 131}$ Sb $_{51}$ isotopes