Nuclear Theory·nucl-th

Friday·March 1, 2019

13 papers—6 primary·7 cross-listed

01
[Submitted on 27 Feb 2019]
Electromagnetic Scattering in Degenerate and Partially Degenerate Nuclear Matter
Stephan Stetina🇦🇹
I calculate the rate of electromagnetic scattering in degenerate and partially degenerate plasmas composed of electrons, muons, protons, and neutrons. Correlations with strong interactions, induced by the polarizability of electromagnetically and strongly charged protons, are taken into account. At subnuclear densities induced interactions are shown to cause a drastic increase of the longitudinal scattering rate. The results obtained are particularly relevant for the electron contribution to transport in the outer core of neutron stars, and represent a first step towards a realistic calculation of transport phenomena in neutron star mergers.
Comments:
35 pages, 24 figures
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1902.10745 [pdf]
1 citation
02
[Submitted on 28 Feb 2019]
Dressed Quark Tensor Vertex and Nucleon Tensor Charge
Langtian Liu🇨🇳 · Lei Chang🇨🇳 · Yu-xin Liu🇨🇳
We construct the quark-antiquark scattering kernels of Bethe-Salpeter equation from the quark self-energy directly under two specific forms of quark-gluon vertices. The quark dressed tensor vertex is then calculated within this consistent framework and rainbow-ladder(RL) approximation. After employing a simplified nucleon model, the nucleon tensor charge can be defined with the tensor vertex. We then compute the tensor charge with the bare tensor vertex and the dressed vertices obtained in this framework and in RL approximation. The obtained results are consistent with the lattice QCD calculations. We also find that typically the gluon dressing effects suppress the nucleon tensor charge compared to the bare tensor vertex, by about $23%$ for RL approximation, and turn to be about $13%$ in this framework.
Comments:
9 pages, 6 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1902.10917 [pdf]
PRD(2019)·11 citations
03
[Submitted on 28 Feb 2019]
Reexamination of the $β^{+}$ decay process of $^{13} N$ nucleus
B.F. Irgaziev · Jameel-Un Nabi · Abdul Kabir
It is known from the scattering theory that the phase-shift of elastic collision does not provide a unique potential to describe the bound state of the two-particle system. The bound state wave function is the most crucial input for various nuclear processes bearing astrophysical significance. In this paper, we emphasize on the important role of the asymptotic normalization coefficients for description of the $^{13} N ⟶^{13} C + β^{+} + ν_{e}$ reaction. Using experimental data of the elastic scattering phase-shift of proton and neutron on $^{12} C$ , we find the asymptotic normalization coefficients which determine the tail of the bound state wave functions. This allows us to modify the wave functions of $^{13} N$ and $^{13} C$ within the single-particle approach using the inverse scattering theory. These wave functions are used to determine the nuclear matrix element for calculation of the half-life and log{\textit ft} values of $β^{+}$ decay of $^{13} N$ . The calculated values of the log{\textit ft} and half-life are smaller than the measured values when the single-particle wave functions are employed. Using overlap functions, instead of single-particle functions, we obtain a better comparison. The overlap function is represented as the product of single-particle function and the corresponding spectroscopic factor.
Comments:
21 pages, 7 figures 1 table
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1902.10925 [pdf]
0 citations
04
[Submitted on 28 Feb 2019]
Low-energy dipole excitation modes in $^{10}$ Be
Yuki Shikata · Yoshiko Kanada-En'yo · Hiroyuki Morita
Low-energy dipole excitations in $^{10}$ Be were investigated based on the generator coordinate method with $α +^{6}$ He and $α + α + 2 n$ cluster models. We obtained three $1^{-}$ states in $E_{x} < 15$ ~MeV, which show different characters in the $E 1$ , compressive dipole, and toroidal dipole transition strengths. We found the strong toroidal dipole transition in the $1_{1}^{-}$ state, remarkable $E 1$ strength in the $1_{2}^{-}$ state, and the strong $E 1$ and compressive dipole strength in the $1_{3}^{-}$ state. The $1_{1}^{-}$ is described by the $α +^{6}$ He cluster structure, where as the $1_{2}^{-}$ and $1_{3}^{-}$ states are understood by three-body excitations of the $α + α + 2 n$ clustering.
Comments:
20 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1902.10962 [pdf]
PTEP(2019)·8 citations
05
[Submitted on 28 Feb 2019]
Energy-weighted sum rule for nuclear density functional theory
Nobuo Hinohara
The expressions for the energy-weighted sum rule of the isoscalar and isovector coordinate operators are derived based on the second-order fluctuation of the local densities. Conventional derivation of the Thouless theorem for the energy-weighted sum rule is based on the double commutator of the Hamiltonian, while the present derivation does not assume a Hamiltonian operator and is applicable to nuclear energy density functionals. The expressions include the contribution of the local gauge symmetry breaking of the energy density functional. It is shown that the local gauge invariance of the kinetic and current densities and kinetic pair density is important, while all the other local densities do not contribute to the energy-weighted sum rule of the coordinate operators. The finite-amplitude method calculations are performed and the expressions for the energy-weighted sum rule are numerically examined for the isoscalar and isovector multipole operators up to $L = 3$ for selected spherical and axially deformed nuclei.
Comments:
17 pages, 4 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1902.11005 [pdf]
PRC(2019)·7 citations
06
[Submitted on 28 Feb 2019]
Examination of Flow and Non-Flow Factorization Methods in Small Collision Systems
S.H. Lim🇺🇸 · Q. Hu🇺🇸 · R. Belmont🇺🇸 · K.K. Hill🇺🇸 · J.L. Nagle🇺🇸 · D.V. Perepelitsa🇺🇸
Two particle correlations have been used extensively to study hydrodynamic flow patterns in heavy-ion collisions. In small collision systems, such as $p$ $+$ $p$ and $p$ $+$ $A$ , where particle multiplicities are much smaller than in $A$ $+$ $A$ collisions, non-flow effects from jet correlations, momentum conservation, particle decays, etc. can be significant, even when imposing a large pseudorapidity gap between the particles. A number of techniques to subtract the non-flow contribution in two particle correlations have been developed by experiments at the Large Hadron Collider (LHC) and then used to measure particle flow in $p$ $+$ $p$ and $p$ $+$ Pb collisions. Recently, experiments at the Relativistic Heavy Ion Collider (RHIC) have explored the possibility of adopting these techniques for small collision systems at lower energies. In this paper, we test these techniques using Monte Carlo generators PYTHIA and HIJING, which do not include any collective flow, and AMPT, which does. We find that it is crucial to examine the results of such tests both for correlations integrated over particle transverse momentum $p_{T}$ and differentially as a function of $p_{T}$ . Our results indicate reasonable non-flow subtraction for $p$ $+$ $p$ collisions at the highest LHC energies, while failing if applied to $p$ $+$ $p$ collisions at RHIC. In the case of $p$ $+$ Au collisions at RHIC, both HIJING and AMPT results indicate a substantial over-subtraction of non-flow for $p_{T} ≳ 1 GeV / c$ and hence an underestimate of elliptic flow.
Comments:
27 pages, 28 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1902.11290 [pdf]
PRC(2019)·33 citations
07
[Submitted on 27 Feb 2019] (cross-list from hep-ph)
Chiral imbalance in hadron matter : its manifestation in photon polarization asymmetries
A.A.Andrianov🇷🇺 · V.A.Andrianov🇷🇺 · D.Espriu🇪🇸 · A.V.Iakubovich🇷🇺 · A.E.Putilova🇷🇺
The possibility of the formation of a local parity breaking (LPB) in a quark-hadron medium is examined as a result of chiral symmetry violation, i.e, the appearance of difference between the average densities of right- and left-handed quarks in the fireball after heavy-ion collisions (HIC). Using the effective meson Lagrangian motivated by QCD extended to the chiral medium the properties of light scalar and pseudoscalar mesons are analyzed. It is establish that exotic decays of scalar mesons arise due to mixing of $π$ and $a_{0}$ vacuum states in the presence of chiral imbalance. The pion electromagnetic formfactor obtains a parity-odd supplement which generates a photon polarization asymmetry in pion polarizability. We conjecture that the above-mentioned properties of LPB can be revealed in experiments on LHC, RHIC, FAIR and NICA accelerators.
Comments:
7 pages, talk on Int. Conf. Hadron Structure and QCD 2018 dedicated to the memory of Lev N. Lipatov. arXiv admin note: substantial text overlap with arXiv:1710.01760
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1902.10705 [pdf]
Phys.Part.Nucl.Lett.(2019)·3 citations
08
[Submitted on 27 Feb 2019] (cross-list from astro-ph.HE)
Finite-temperature extension for cold neutron star equations of state
Carolyn A. Raithel · Feryal Ozel · Dimitrios Psaltis
Observations of isolated neutron stars place constraints on the equation of state (EOS) of cold, neutron-rich matter, while nuclear physics experiments probe the EOS of hot, symmetric matter. Many dynamical phenomena, such as core-collapse supernovae, the formation and cooling of proto-neutron stars, and neutron star mergers, lie between these two regimes and depend on the EOS at finite temperatures for matter with varying proton fractions. In this paper, we introduce a new framework to accurately calculate the thermal pressure of neutron-proton-electron matter at arbitrary density, temperature, and proton fraction. This framework can be expressed using a set of five physically-motivated parameters that span a narrow range of values for realistic EOS and are able to capture the leading-order effects of degenerate matter on the thermal pressure. We base two of these parameters on a new approximation of the Dirac effective mass, with which we reproduce the thermal pressure to within <~30% for a variety of realistic EOS at densities of interest. Three additional parameters, based on the behavior of the symmetry energy near the nuclear saturation density, allow for the extrapolation of any cold EOS in beta-equilibrium to arbitrary proton fractions. Our model thus allows a user to extend any cold nucleonic EOS, including piecewise-polytropes, to arbitrary temperature and proton fraction, for use in calculations and numerical simulations of astrophysical phenomena. We find that our formalism is able to reproduce realistic finite-temperature EOS with errors of <~20% and offers a 1-3 orders-of-magnitude improvement over existing ideal-fluid models.
Comments:
Accepted for publication in ApJ
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1902.10735 [pdf]
ApJ(2019)·88 citations
09
[Submitted on 28 Feb 2019] (cross-list from hep-ph)
Nature of the $Y (4260)$ : A light-quark perspective
Yun-Hua Chen🇨🇳 · Ling-Yun Dai🇨🇳 · Feng-Kun Guo🇨🇳 · Bastian Kubis🇩🇪
The $Y (4260)$ has been one of the most puzzling pieces among the so-called $X Y Z$ states. In this paper, we try to gain insights into the structure of the $Y (4260)$ from the light-quark perspective. We study the dipion invariant mass spectrum of the $e^{+} e^{-} \to Y (4260) \to J / ψ π^{+} π^{-}$ process and the ratio of the cross sections $σ (e^{+} e^{-} \to J / ψ K^{+} K^{-}) / σ (e^{+} e^{-} \to J / ψ π^{+} π^{-})$ . In particular, we consider the effects of different light-quark SU(3) eigenstates inside the $Y (4260)$ . The strong pion-pion final-state interactions as well as the $K K ˉ$ coupled channel in the $S$ -wave are taken into account in a model-independent way using dispersion theory. We find that the SU(3) octet state plays a significant role in these transitions, implying that the $Y (4260)$ contains a large light-quark component. Our findings suggest that the $Y (4260)$ is neither a hybrid nor a conventional charmonium state, and they are consistent with the $Y (4260)$ having a sizeable $D ˉ D_{1}$ component which, however, is not completely dominant.
Comments:
22 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1902.10957 [pdf]
PRD(2019)·44 citations
10
[Submitted on 28 Feb 2019] (cross-list from cond-mat.quant-gas)
Generalized Crossover in Interacting Fermions within the Low-Energy Expansion
Hiroyuki Tajima
We generalize the Bardeen-Cooper-Schrieffer-Bose-Einstein-condensation (BCS-BEC) crossover of two-component fermions, which is realized by tuning the $s$ -wave scattering length $a$ between the fermions, to the case of an arbitrary effective range $r_{e}$ . By using the Nozières-Schmitt-Rink (NSR) approach, we show another crossover by changing $r_{e}$ and present several similarities and differences between these two crossovers. Furthermore, the region ( $r_{e} > a /2$ ) where the effective range expansion breaks down and the Hamiltonian becomes non-Hermitian is found, being consistent with the Wigner's causality bound. Our results are universal for low-density interacting fermions with low-energy constants $a$ and $r_{e}$ and are directly relevant to ultracold Fermi atomic gases as well as dilute neutron matter.
Comments:
6 pages, 4 figures, accepted by J. Phys. Soc. Jpn
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
1902.11081 [pdf]
J.Phys.Soc.Jap.(2019)·6 citations
11
[Submitted on 28 Feb 2019] (cross-list from physics.data-an)
Determination of the quark-gluon string parameters from the data on pp, pA and AA collisions at wide energy range using Bayesian Gaussian Process Optimization
Vladimir Kovalenko (Saint Petersburg State University)🇷🇺
Bayesian Gaussian Process Optimization can be considered as a method of the determination of the model parameters, based on the experimental data. In the range of soft QCD physics, the processes of hadron and nuclear interactions require using phenomenological models containing many parameters. In order to minimize the computation time, the model predictions can be parameterized using Gaussian Process regression, and then provide the input to the Bayesian Optimization. In this paper, the Bayesian Gaussian Process Optimization has been applied to the Monte Carlo model with string fusion. The parameters of the model are determined using experimental data on multiplicity and cross section of pp, pA and AA collisions at wide energy range. The results provide important constraints on the transverse radius of the quark-gluon string ( $r_{s t r}$ ) and the mean multiplicity per rapidity from one string ( $μ_{0}$ ).
Comments:
9 pages, 5 figures, proc. XIIIth Quark Confinement and the Hadron Spectrum
Subjects:
Data Analysis, Statistics and Probability (physics.data-an); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1902.11082 [pdf]
PoS(2019)·1 citation
12
[Submitted on 28 Feb 2019] (cross-list from nucl-ex)
Shape staggering of mid-shell mercury isotopes from in-source laser spectroscopy compared with Density Functional Theory and Monte Carlo Shell Model calculations
S. Sels🇧🇪 · T. Day Goodacre🇬🇧 · B. A. Marsh🇨🇭 · A. Pastore🇬🇧 · W. Ryssens🇫🇷 · Y. Tsunoda🇯🇵 · N. Althubiti🇬🇧 · B. Andel🇸🇰 · A. N. Andreyev🇬🇧 · D. Atanasov🇩🇪 · A. E. Barzakh🇷🇺 · M. Bender🇫🇷 and 36 other authors
Neutron-deficient $^{177 - 185}$ Hg isotopes were studied using in-source laser resonance-ionization spectroscopy at the CERN-ISOLDE radioactive ion-beam facility, in an experiment combining different detection methods tailored to the studied isotopes. These include either alpha-decay tagging or Multi-reflection Time-of-Flight gating to identify the isotopes of interest. The endpoint of the odd-even nuclear shape staggering in mercury was observed directly by measuring for the first time the isotope shifts and hyperfine structures of $^{177 - 180}$ Hg. Changes in the mean-square charge radii for all mentioned isotopes, magnetic dipole and electric quadrupole moments of the odd-A isotopes and arguments in favor of $I = 7/2$ spin assignment for $^{177, 179}$ Hg were deduced. Experimental results are compared with Density Functional Theory (DFT) and Monte-Carlo Shell Model (MCSM) calculations. DFT calculations with several Skyrme parameterizations predict a large jump in the charge radius around the neutron $N = 104$ mid shell, with an odd-even staggering pattern related to the coexistence of nearly-degenerate oblate and prolate minima. This near-degeneracy is highly sensitive to many aspects of the effective interaction, a fact that renders perfect agreement with experiment out of reach for current functionals. Despite this inherent diffculty, the SLy5s1 and a modified UNEDF1^{SO} parameterization predict a qualitatively correct staggering that is off by two neutron numbers. MCSM calculations of states with the experimental spins and parities show good agreement for both electromagnetic moments and the observed charge radii. A clear mechanism for the origin of shape staggering within this context is identified: a substantial change in occupancy of the proton $π h_{9/2}$ and neutron $ν i_{13/2}$ orbitals.
Comments:
19 pages, 18 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1902.11211 [pdf]
PRC(2019)·65 citations
13
[Submitted on 28 Feb 2019] (cross-list from hep-ph)
Novel Method for Precisely Measuring the $X (3872)$ Mass
Feng-Kun Guo🇨🇳
The $X (3872)$ is the first and the most interesting one amongst the abundant $X Y Z$ states. Its mass coincides exactly with the $D^{0} D ˉ^{* 0}$ threshold with an uncertainty of 180 keV. Precise knowledge of its mass is crucial to understand the $X (3872)$ . However, whether it is above or below the $D^{0} D ˉ^{* 0}$ threshold is still unknown. We propose a completely new method to measure the $X (3872)$ mass precisely by measuring the $X (3872) γ$ line shape between 4010 and 4020 MeV, which is strongly sensitive to the $X (3872)$ mass relative to the $D^{0} D ˉ^{* 0}$ threshold due to a triangle singularity. This method can be applied to experiments which produce copious $D^{* 0} D ˉ^{* 0}$ pairs, such as electron-positron, proton-antiproton and other experiments, and may lead to much more precise knowledge about the $X (3872)$ mass.
Comments:
Version to be published in Phys. Rev. Lett
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1902.11221 [pdf]
PRL(2019)·77 citations

Affiliations

first authorsco-authorsvia INSPIRE