Nuclear Theory·nucl-th

Wednesday·August 29, 2018

9 papers—3 primary·6 cross-listed

01
Relativistic Brueckner-Hartree-Fock in nuclear matter without the average momentum approximation
Hui Tong · Xiu-Lei Ren · Peter Ring · Shi-Hang Shen · Si-Bo Wang · Jie Meng
Brueckner-Hartree-Fock theory allows to derive the $G$ -matrix as an effective interaction between nucleons in the nuclear medium. It depends on the center of mass momentum $P$ of the two particles and on the two relative momenta $q$ and $q^{'}$ before and after the scattering process. In the evaluation of the total energy per particle in nuclear matter usually the angle averaged center of mass momentum approximation has been used. We derive in detail the exact expressions of the angular integrations of the momentum $P$ within relativistic Brueckner-Hartree-Fock (RBHF) theory, especially for the case of asymmetric nuclear matter. In order to assess the reliability of the conventional average momentum approximation for the binding energy, the saturation properties of symmetric and asymmetric nuclear matter are systematically investigated based on the realistic Bonn nucleon-nucleon potential. It is found that the exact treatment of the center of mass momentum leads to non-negligible contributions to the higher order physical quantities. The correlation between the symmetry energy $E_{sym}$ , the slope parameter $L$ , and the curvature $K_{sym}$ of the symmetry energy are investigated. The results of our RBHF calculations for the bulk parameters characterizing the equation of state are compared with recent constraints extracted from giant monopole resonance and isospin diffusion experiments.
nucl-thPRC(2018)·46 citations
02
Nuclear structure studies of double Gamow-Teller strength
N. Auerbach · Bui Minh Loc
The double Gamow-Teller strength distributions in even- $A$ Calcium isotopes were calculated using the nuclear shell model by applying the single Gamow-Teller operator two times sequentially on the ground state of the parent nucleus. The number of intermediate states actually contributing to the results was determined. The sum rules for the double Gamow-Teller operator in the full calculation were approximately fulfilled. In the case that the symmetry is restored approximately by introducing degeneracies of the $f$ -levels, and the $p$ -levels in the $f p$ -model space, the agreement with the sum rules was very close.
nucl-thPRC(2018)·12 citations
03
Binding-energy independence of reduced spectroscopic strengths derived from (p, 2p) and (p, pn) reactions with nitrogen and oxygen isotopes
M. Gómez-Ramos · A.M. Moro
A campaign of intermediate energy (300-450 MeV/u) proton-induced nucleon knockout measurements in inverse kinematics has been recently undertaken at the R 3 B/LAND setup at GSI. We present a systematic theoretical analysis of these data with the aim of studying the quenching of the single-particle strengths and its binding-energy dependence. For that, the measured semi-inclusive (p, 2p) and (p, pn) cross sections are compared with theoretical predictions based on single-particle cross sections derived from a novel coupled-channels formalism and shell-model spectroscopic factors. A systematic reduction of about 20-30% is found, with a very limited dependence on proton-neutron asymmetry.
nucl-thnucl-exPLB(2018)·54 citations
04
DUNE as the Next-Generation Solar Neutrino Experiment
Francesco Capozzi🇺🇸 · Shirley Weishi Li🇺🇸 · Guanying Zhu🇺🇸 · John F. Beacom🇺🇸
We show that the Deep Underground Neutrino Experiment (DUNE), with significant but feasible new efforts, has the potential to deliver world-leading results in solar neutrinos. With a 100 kton-year exposure, DUNE could detect $≳ 1 0^{5}$ signal events above 5 MeV electron energy. Separate precision measurements of neutrino-mixing parameters and the $^{8}$ B flux could be made using two detection channels ( $ν_{e} +^{40}$ Ar and $ν_{e, μ, τ} + e^{-}$ ) and the day-night effect ( $> 10 σ$ ). New particle physics may be revealed through the comparison of solar neutrinos (with matter effects) and reactor neutrinos (without), which is discrepant by $\sim 2 σ$ (and could become $5.6 σ$ ). New astrophysics may be revealed through the most precise measurement of the $^{8}$ B flux (to 2.5\%) and the first detection of the {\it hep} flux (to 11\%). {\it DUNE is required:} No other experiment, even proposed, has been shown capable of fully realizing these discovery opportunities.
↳ hep-phastro-ph.SRhep-exnucl-th+1PRL(2019)·164 citations
05
Quark-mass dependence in $ω \to 3 π$ decays
Maximilian Dax🇩🇪 · Tobias Isken🇩🇪 · Bastian Kubis🇩🇪
We study the quark-mass dependence of $ω \to 3 π$ decays, based on a dispersion-theoretical framework. We rely on the quark-mass-dependent scattering phase shift for the pion-pion $P$ -wave extracted from unitarized chiral perturbation theory. The dispersive representation then takes into account the final-state rescattering among all three pions. The described formalism may be used as an extrapolation tool for lattice QCD calculations of three-pion decays, for which $ω \to 3 π$ can serve as a paradigm case.
↳ hep-phhep-latnucl-thEPJC(2018)·40 citations
06
Small- $x$ Helicity Evolution: an Operator Treatment
Yuri V. Kovchegov🇺🇸 · Matthew D. Sievert🇺🇸
We rederive the small- $x$ evolution equations governing quark helicity distribution in a proton using solely an operator-based approach. In our previous works on the subject, the evolution equations were derived using a mix of diagrammatic and operator-based methods. In this work, we re-derive the double-logarithmic small- $x$ evolution equations for quark helicity in terms of the "polarized Wilson lines", the operators consisting of light-cone Wilson lines with one or two non-eikonal local operator insertions which bring in helicity dependence. For the first time we give explicit and complete expressions for the quark and gluon polarized Wilson line operators, including insertions of both the gluon and quark sub-eikonal operators. We show that the double-logarithmic small- $x$ evolution of the "polarized dipole amplitude" operators, made out of regular light-cone Wilson lines along with the polarized ones constructed here, reproduces the equations derived in our earlier works. The method we present here can be used as a template for determining the small- $x$ asymptotics of any transverse momentum-dependent (TMD) quark (or gluon) parton distribution functions (PDFs), and is not limited to helicity.
↳ hep-phnucl-thPRD(2019)·117 citations
07
Robustness of anomaly-related magnetoresistance in doped Weyl semimetals
Hiroaki Ishizuka🇯🇵 · Naoto Nagaosa🇯🇵
Weyl semimetal with Weyl fermions at Fermi energy is one of the topological materials, and is a condensed-matter realization of the relativistic fermions. However, there are several crucial differences such as the shift of Fermi energy, which can hinder the expected interesting physics. Chiral anomaly is a representative nontrivial phenomenon associated with Weyl fermions, which dictates the transfer of fermions between the Weyl fermions with opposite chirality; it is manifested as the negative magnetoresistance. Here we demonstrate that the magnetoresistance is robust against the deviation from the ideal Weyl Hamiltonian such as the shifted Fermi energy and nonlinear dispersions. We study a model with the energy dispersion containing two Weyl nodes, and find that the magnetoresistance persists even when the Fermi level is far away from the node, even above the saddle point that separates the two nodes. Surprisingly, the magnetoresistance remains even after the pair annihilation of the nodes.
↳ cond-mat.mes-hallcond-mat.str-elnucl-thPRB(2019)·6 citations
08
Two-photon exchange correction to the Lamb shift and hyperfine splitting of S levels
Oleksandr Tomalak🇩🇪
We evaluate the two-photon exchange corrections to the Lamb shift and hyperfine splitting of S states in electronic hydrogen relying on modern experimental data and present the two-photon exchange on a neutron inside the electronic and muonic atoms. These results are relevant for the precise extraction of the isotope shift as well as in the analysis of the ground state hyperfine splitting in usual and muonic hydrogen.
↳ hep-phnucl-exnucl-thphysics.atom-phEPJA(2019)·49 citations
09
Study of charged particle multiplicity, average transverse momentum and azimuthal anisotropy in Xe+Xe collisions at $s_{N N}$ = 5.44 TeV using AMPT model
Sourav Kundu🇮🇳 · Dukhishyam Mallick🇮🇳 · Bedangadas Mohanty🇮🇳
We have studied the average charged particle density ( $<$ dN $_{c h}$ /d $η$ $>$ ), transverse momentum ( $p_{T}$ ) spectra, $<$ $p_{T}$ $>$ and azimuthal anisotropies of inclusive charged particles produced in Xe+Xe collisions at $s_{N N}$ = 5.44 TeV using A Multiphase Transport Model (AMPT), which includes the deformation of Xe $^{129}$ nucleus. Calculations have been performed with the string melting version of AMPT model and compared with the recent measurements from the ALICE experiment. The model results over predict the measured $<$ dN $_{c h}$ /d $η$ $>$ for central collisions, agree with the data for mid-central collisions and under predict the measurements for peripheral collisions. The centrality dependence of $<$ $p_{T}$ $>$ of charged particles measured in ALICE is not reproduced by the model results. The calculated elliptic flow ( $v_{2}$ ) from AMPT model overpredicts the ALICE measurements in central collisions but are consistent with the data in mid central collisions. We find that the model shows a mild centrality dependence of triangular flow and overestimates the ALICE measurements. Within the model framework, we have also studied various collision configurations of Xe nuclei such as body-body, tip-tip, side-side and random. We find a strong dependence of the above observable on the collision configurations.
↳ nucl-exhep-exnucl-thEPJA(2019)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE