Nuclear Theory·nucl-th

Thursday·October 10, 2019

8 papers—5 primary·3 cross-listed

01
Baseline predictions of elliptic flow and fluctuations at the RHIC Beam Energy Scan using response coefficients
S. Rao🇺🇸 · M. Sievert🇺🇸 · J. Noronha-Hostler🇺🇸
Currently the RHIC Beam Energy Scan is exploring a new region of the Quantum Chromodynamic phase diagram at large baryon densities that approaches nuclear astrophysics regimes. This provides an opportunity to study relativistic hydrodynamics in a regime where the net conserved charges of baryon number, strangeness, and electric charge play a role, which will significantly change the theoretical approach to simulating the baryon-dense Quark-Gluon Plasma. Here we detail many of the important changes needed to adapt both initial conditions and the medium to baryon-rich matter. Then, we make baseline predictions for the elliptical flow and fluctuations based on extrapolating the physics at LHC and top RHIC energies to support future analyses of where and how the new baryon-dense physics causes these extrapolations to break down. First we compare eccentricities across beam energies, exploring their underlying assumptions; we find the the extrapolated initial state is predicted to be nearly identical to that at AuAu $s_{N N} = 200$ GeV. Then the final flow harmonic predictions are based on linear+cubic response. We discuss preliminary STAR results in order to determine the implications that they have for linear+cubic response coefficients at the lowest beam energy of AuAu $s_{N N} = 7$ GeV.
nucl-thhep-exhep-phPRC(2021)·43 citations
02
Density functional theory for nuclear fission -- a proposal
J. Dobaczewski
The fission process is a fascinating phenomenon in which the atomic nucleus, a compact self-bound mesoscopic system, undergoes a spontaneous or induced quantum transition into two or more fragments. A predictive, accurate and precise description of nuclear fission, rooted in a fundamental quantum many-body theory, is one of the biggest challenges in science. Current approaches assume adiabatic motion of the system with internal degrees of freedom at thermal equilibrium. With parameters adjusted to data, such modelling works well in describing fission lifetimes, fragment mass distributions, or their total kinetic energies. However, are the assumptions valid? For the fission occurring at higher energies and/or shorter times, the process is bound to be non-adiabatic and/or non-thermal. The vision of this project is to go beyond these approximations, and to obtain a unified description of nuclear fission at varying excitation energies. The key elements of this project are the use of nuclear density functional theory with novel, nonlocal density functionals and innovative high-performance computing techniques. Altogether, the project aims at better understanding of nuclear fission, where slow, collective, and semi-classical effects are intertwined with fast, microscopic, quantum evolution.
nucl-th6 citations
03
Triangular symmetry in cluster nuclei
R. Bijker · A.H. Santana-Valdés
In this contribution, we present evidence for the occurrence of triangular symmetry in cluster nuclei. We discuss the structure of rotational bands for 3-alpha and 3-alpha+1 configurations with triangular D(3h) symmetry by exploiting the double group D'(3h), and study the application to 12C and 13C. The structure of rotational bands can be used as a fingerprint of the underlying geometric configuration of alpha-particles.
nucl-thnucl-exJ.Phys.Conf.Ser.(2020)·1 citation
04
Taming nuclear complexity with a committee of multilayer neural networks
R.-D. Lasseri🇫🇷 · D. Regnier🇫🇷 · J.-P. Ebran🇫🇷 · A. Penon
We demonstrate that a committee of deep neural networks is capable of predicting the ground-state and excited energies of more than 1800 atomic nuclei with an accuracy akin to the one achieved by state-of-the-art nuclear energy density functionals (EDFs) and a major speed-up. An active learning strategy is proposed to train this algorithm with a minimal set of 210 nuclei. This approach enables future fast studies of the influence of EDFs parametrizations on structure properties over the whole nuclear chart and suggests that for the first time an artificial intelligence successfully encoded the laws of nuclear deformation.
nucl-thphysics.comp-phPRL(2020)·83 citations
05
Short-range correlations for neutrinoless double-beta decay and low-momentum NN potentials
L. Coraggio🇮🇹 · N. Itaco🇮🇹 · R. Mancino🇮🇹
We approach the calculation of the nuclear matrix element of the neutrinoless double-beta decay process, considering the light-neutrino-exchange channel, by way of the realistic shell-model. In particular the focus of our work is spotted on the role of the short-range correlations, which should be taken into account because of the short-range repulsion of the realistic potentials. Our shell-model wave functions are calculated using an effective Hamiltonian derived from the high-precision CD-Bonn nucleon-nucleon potential, the latter renormalized by way of the so-called V-low-k approach. The renormalization procedure decouples the repulsive high-momentum component of the potential from the low-momentum ones by the introduction of a cutoff Lambda, and is employed to renormalize consistently the two-body neutrino potentials to calculate the nuclear matrix elements of candidates to this decay process in mass interval ranging from A=76 up to A=136. We study the dependence of the decay operator on the choice of the cutoff, and compare our results with other approaches that can be found in present literature.
nucl-thJ.Phys.Conf.Ser.(2020)·8 citations
06
An effective field theory approach to quarkonium at small transverse momentum
Sean Fleming🇺🇸 · Yiannis Makris🇮🇹 · Thomas Mehen🇺🇸
In this work we apply effective field theory (EFT) to observables in quarkonium production and decay that are sensitive to soft gluon radiation, in particular measurements that are sensitive to small transverse momentum. Within the EFT framework we study $χ_{Q}$ decay to light quarks followed by the fragmentation of those quarks to light hadrons. We derive a factorization theorem that involves transverse momentum distribution (TMD) fragmentation functions and new quarkonium TMD shape functions. We derive renormalization group equations, both in rapidity and virtuality, which are used to evolve the different terms in the factorization theorem to resum large logarithms. This theoretical framework will provide a systematic treatment of quarkonium production and decay processes in TMD sensitive measurements.
↳ hep-phnucl-thJHEP(2020)·61 citations
07
Heavy-flavour observables in relativistic nuclear collisions: theory overview
Andrea Beraudo🇮🇹
Transport calculations represent the major tool to simulate the modifications induced by the presence of a hot-deconfined medium on the production of heavy-flavour particles in high-energy nuclear collisions. After a brief description of the approach and of the major achievements in its phenomenological applications we discuss some recent developments. From the theory side we focus on the evaluation of transport coefficients and on recent formulations of the problem of heavy-flavour in-medium propagation in the language of open quantum systems. From a more phenomenological perspective we give an overview of the attempts to extend theoretical models to reproduce recent experimental data arising from event-by-event fluctuations (odd flow harmonics, event-shape-engineering) or from medium-modifications of hadronization ( $D_{s}$ and $Λ_{c}$ production)
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2020)·0 citations
08
Crust of accreting neutron stars within simplified reaction network
Nikolay N. Shchechilin · Andrey I. Chugunov (Ioffe Institute)
Transiently accreting neutron stars in low mass X-ray binaries are generally believed to be heated up by nuclear reactions in accreted matter during hydrostatic compression. Detailed modeling of these reactions is required for the correct interpretation of observations. In this paper, we construct a simplified reaction network, which can be easily implemented and depends mainly on atomic mass tables as nuclear physics input. We show that it reproduces results of the detailed network by Lau et al. (2018) very well, if one applies the same mass model. However, the composition and the heating power are shown to be sensitive to the mass table used and treatment of mass tables boundary, if one applies several of them in one simulation. In particular, the impurity parameter $Q_{imp}$ at density $ρ = 2 \times 1 0^{12}$ g cm $^{- 3}$ can differ for a factor of few, and even increase with density increase. The profile of integrated heat realize shown to be well confined between results by Fantina et al. (2018) and Lau et al. (2018).
↳ astro-ph.HEastro-ph.SRnucl-thMNRAS(2019)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE