Nuclear Theory·nucl-th

Wednesday·October 7, 2020

14 papers—6 primary·8 cross-listed

01
Nuclear de-excitations in low-energy charged-current $ν_{e}$ scattering on $^{40}$ Ar
S. Gardiner (Fermi National Accelerator Laboratory)🇺🇸
Background: Large argon-based neutrino detectors, such as those planned for the Deep Underground Neutrino Experiment, have the potential to provide unique sensitivity to low-energy (few to tens of MeV) electron neutrinos produced by core-collapse supernovae. Despite their importance for neutrino energy reconstruction, nuclear de-excitations following charged-current $ν_{e}$ absorption on $^{40}$ Ar have never been studied in detail at supernova energies. Purpose: I develop a model of nuclear de-excitations that occur following the $^{40} Ar (ν_{e}, e^{-})^{40} K^{*}$ reaction. This model is applied to the calculation of exclusive cross sections. Methods: A simple expression for the inclusive differential cross section is derived under the allowed approximation. Nuclear de-excitations are described using a combination of measured $γ$ -ray decay schemes and the Hauser-Feshbach statistical model. All calculations are carried out using a novel Monte Carlo event generator called MARLEY (Model of Argon Reaction Low Energy Yields). Results: Various total and differential cross sections are presented. Two de-excitation modes, one involving only $γ$ -rays and the other including single neutron emission, are found to be dominant at few tens-of-MeV energies. Conclusions: Nuclear de-excitations have a strong impact on the achievable energy resolution for supernova $ν_{e}$ detection in liquid argon. Tagging events involving neutron emission, though difficult, could substantially improve energy reconstruction. Given a suitable calculation of the inclusive cross section, the MARLEY nuclear de-excitation model may readily be applied to other scattering processes.
nucl-thPRC(2021)·42 citations
02
Daejeon16 interaction with contact-term corrections for heavy nuclear systems
Panagiota Papakonstantinou · James P. Vary · Youngman Kim
The Daejeon16 two-nucleon interaction is employed in many-body approaches based on the mean-field approximation. The perturbative character of Daejeon16 is verified by comparing results for 16O from the Hartree-Fock (HF) approximation and from the no-core shell model and by examining the magnitude of perturbative corrections to the HF energy in light and heavy nuclei. In order to approximately describe energies and radii across the nuclear chart, a phenomenological correction in the form of a two-plus-three-nucleon contact interaction is introduced. With fitted parameters we achieve a very good description of medium-mass nuclei in terms of energy and size and also in terms of the centroid energy of the giant monopole resonance and the dipole polarizability calculated within the random-phase approximation (RPA). Our results provide further justification for the use of Daejeon16 augmented with phenomenological corrections as an effective interaction of perturbative character in a variety of applications.
nucl-thJ.Phys.G(2021)·5 citations
03
Neutron skin thickness of $^{208}$ Pb determined from reaction cross section for proton scattering
Shingo Tagami · Tomotsugu Wakasa · Jun Matsui · Maya Takechi · Masanobu Yahiro
The reaction cross section $σ_{R}$ is useful to determine the neutron radius $R_{n}$ as well as the matter radius $R_{m}$ . The chiral (Kyushu) $g$ -matrix folding model for $^{12}$ C scattering on $^{9}$ Be, $^{12}$ C, $^{27}$ Al targets was tested in the incident energy range of $30 \lsim E_{in} \lsim 400$ MeV, and it is found that the model reliably reproduces the $σ_{R}$ in $30 \lsim E_{in} \lsim 100$ MeV and $250 \lsim E_{in} \lsim 400$ MeV. \item[Aim] We determine $R_{n}$ and the neutron skin thickness $R_{skin}$ of $^{208} Pb$ by using high-quality $σ_{R}$ data for the $p +^{208} Pb$ scattering in $30 \leq E_{in} \leq 100$ MeV. The theoretical model is the Kyushu $g$ -matrix folding model with the densities calculated with Gongny-D1S HFB (GHFB) with the angular momentum projection (AMP). \item[Results] The Kyushu $g$ -matrix folding model with the GHFB+AMP densities underestimates $σ_{R}$ in $30 \leq E_{in} \leq 100$ ~MeV only by a factor of 0.97. Since the proton radius $R_{p}$ calculated with GHFB+AMP agrees with the precise experimental data of 5.444 fm, the small deviation of the theoretical result from the data on $σ_{R}$ allows us to scale the GHFB+AMP neutron density so as to reproduce the $σ_{R}$ data. In $E_{in}$ = 30--100 MeV, the experimental $σ_{R}$ data can be reproduced by assuming the neutron radius of $^{208} Pb$ as $R_{n}$ = $5.722 \pm 0.035$ fm. \item[Conclusion] The present result $R_{skin}$ = $0.278 \pm 0.035$ fm is in good agreement with the recent PREX-II result of $r_{skin}$ = $0.283 \pm 0.071$ fm.
nucl-thnucl-exPRC(2021)·31 citations
04
Correspondence between Israel-Stewart and first-order causal and stable hydrodynamics for Bjorken-expanding baryon-rich systems with vanishing particle masses
Arpan Das🇵🇱 · Wojciech Florkowski🇵🇱 · Radoslaw Ryblewski🇵🇱
We obtain an exact correspondence between the dynamical equations in Israel-Stewart (IS) theory and first-order causal and stable (FOCS) hydrodynamics for a boost-invariant system with an ideal gas equation of state at finite baryon chemical potential. Explicit expressions for the temperature and chemical potential dependence of the regulators in the FOCS theory are given in terms of the kinetic coefficients and constant relaxation time of the IS theory. Using the correspondence between the IS and FOCS theory, stability conditions for a charged fluid which are known in the FOCS approach are applied and one finds that the IS theory considered is unstable.
nucl-thhep-phPRD(2021)·7 citations
05
Density-dependent nn-potential from subleading chiral three-neutron forces: Long-range terms
N. Kaiser
The long-range terms of the subleading chiral three-nucleon force [published in Phys.\,Rev.\,C77, 064004 (2008)] are specified to the case of three neutrons. From these $3 n$ -interactions an effective density-dependent neutron-neutron potential $V_{med}$ in pure neutron matter is derived. Following the division of the pertinent 3n-diagrams into two-pion exchange, two-pion-one-pion exchange and ring topology, all self-closings and concatenations of two neutron-lines to an in-medium loop are evaluated. The momentum and $k_{n}$ -dependent potentials associated with the spin-operators $1, σ_{1} \cdot σ_{2}, σ_{1} \cdot q σ_{2} \cdot q, i (σ_{1} + σ_{2}) \cdot (q \times p), (σ_{1} \cdot p σ_{2} \cdot p + σ_{1} \cdot p^{'} σ_{2} \cdot p^{'})$ and $σ_{1} \cdot (q \times p) σ_{2} \cdot (q \times p)$ are expressed in terms of functions, which are either given in closed analytical form or require at most one numerical integration. The subsubleading chiral 3N-force is treated in the same way. The obtained results for $V_{med}$ are helpful to implement the long-range chiral three-body forces into advanced neutron matter calculations.
nucl-th9 citations
06
Many-body forces and nucleon clustering near the QCD critical point
Dallas DeMartini🇺🇸 · Edward Shuryak🇺🇸
It has been proposed that one can look for the QCD critical point (CP) by the Beam Energy Scan (BES) accurately monitoring event-by-event fluctuations. This experimental program is under way at the BNL RHIC collider. Separately, it has been studied how clustering of nucleons at freezeout affects proton multiplicity distribution and light nuclei production. It was found that even a minor increase of the range of nuclear forces dramatically increases clustering, while large correlation length $ξ$ near CP makes attraction due to binary forces unrealistically large. In this paper we show that repulsive many-body forces near CP should overcome the binary ones and effectively suppress clustering. We also discuss current experimental data and point out locations at which a certain drop in clustering may already be observed.
nucl-thPRC(2021)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nuclear de-excitations in low-energy charged-current νe​ scattering on 40Ar

Daejeon16 interaction with contact-term corrections for heavy nuclear systems

Neutron skin thickness of 208Pb determined from reaction cross section for proton scattering

Correspondence between Israel-Stewart and first-order causal and stable hydrodynamics for Bjorken-expanding baryon-rich systems with vanishing particle masses

Density-dependent nn-potential from subleading chiral three-neutron forces: Long-range terms

Many-body forces and nucleon clustering near the QCD critical point

Affiliations

Nuclear de-excitations in low-energy charged-current $ν_{e}$ scattering on $^{40}$ Ar

Neutron skin thickness of $^{208}$ Pb determined from reaction cross section for proton scattering