Nuclear Theory·nucl-th

Friday·December 3, 2021

10 papers—7 primary·3 cross-listed

01
Exploring experimental conditions to reduce uncertainties in the optical potential
M. Catacora-Rios · G. B. King · A. E. Lovell · F. M. Nunes
Background: Uncertainty quantification for nuclear theories has gained a more prominent role in the field, with more and more groups attempting to understand the uncertainties on their calculations. However, recent studies have shown that the uncertainties on the optical potentials are too large for the theory to be useful. Purpose: The purpose of this work is to explore possible experimental conditions that may reduced the uncertainties on elastic scattering and single-nucleon transfer cross sections that come from the fitting of the optical model parameters to experimental data. Method: Using Bayesian methods, we explore the effect of the uncertainties of optical model parameters on the angular grid of the differential cross section, including cross section data at nearby energies, and changes in the experimental error bars. We also study the effect on the resulting uncertainty when other observables are included in the fitting procedure, particularly the total (reaction) cross sections. Results: We study proton and neutron elastic scattering on 48Ca and 208Pb. We explore the parameter space with Markov- Chain Monte Carlo, produce posterior distributions for the optical model parameters, and construct the corresponding 95% confidence intervals on the elastic-scattering cross sections. We also propagate the uncertainties on the optical potentials to the 48Ca(d,p)49Ca(g.s.) and 208Pb(d,p)209Pb(g.s.) cross sections. Conclusions: We find little sensitivity to the angular grid and an improvement of up to a factor of 2 on the uncertainties by including data at a nearby energy. Although reducing the error bars on the data does reduce the uncertainty, the gain is often considerably smaller than one would naively expect.
nucl-thPRC(2019)·30 citations
02
Constructing chiral effective field theory around unnatural leading-order interactions
Rui Peng🇨🇳 · Songlin Lyu🇨🇳 · Sebastian König🇺🇸 · Bingwei Long🇨🇳
A momentum-dependent formulation based on a stationary spin-0 and isospin-1 dibaryon field is proposed to improve convergence of chiral effective field theory in the $\cs 10$ channel of $N N$ scattering. Although the two-parameter leading-order interaction appears to be unnatural, it nevertheless has the necessary features of an effective field theory. A rapid order-by-order convergence is found in $\cs 10$ . As an application beyond the two-body level, the triton binding energy is studied and compared to standard chiral effective field theory with partly perturbative pions. The consistency of the chiral Lagrangian for the new formulation is examined by working out the pionic radiative corrections, and consequences of nontrivial chiral-connection terms are discussed.
nucl-thPRC(2022)·21 citations
03
Neutron skin thickness of $^{48}$ Ca, $^{132}$ Sn and $^{208}$ Pb with KIDS density functional
Chang Ho Hyun
Neutron skin thickness ( $R_{n p}$ ) of the atomic nuclei $^{48}$ Ca, $^{132}$ Sn and $^{208}$ Pb are considered in the KIDS (Korea:IBS-Daegu-Sungkyunkwan) density functional formalism. Model parameters most relevant to $R_{n p}$ are constrained from standard nuclear data and neutron star properties determined from modern observations. Mean values of $R_{n p}$ are obtained as 0.161, 0.220 and 0.160 fm for $^{48}$ Ca, $^{132}$ Sn and $^{208}$ Pb, respectively, and the corresponding standard deviations are 0.011, 0.020 and 0.021 fm. Correlations between $R_{n p}$ of the three nuclei are considered, and we find that $R_{n p}$ 's are correlated very strongly. We obtain correlation coefficient 0.978 between $R_{n p}$ of $^{48}$ Ca and $^{208}$ Pb, and 0.996 between $R_{n p}$ of $^{132}$ Sn and $^{208}$ Pb.
nucl-thNew Phys.Sae Mulli(2022)·4 citations
04
Ab initio predictions link the neutron skin of $^{208}$ Pb to nuclear forces
Baishan Hu · Weiguang Jiang · Takayuki Miyagi · Zhonghao Sun · Andreas Ekström · Christian Forssén · Gaute Hagen · Jason D. Holt · Thomas Papenbrock · S. Ragnar Stroberg · Ian Vernon
Heavy atomic nuclei have an excess of neutrons over protons, which leads to the formation of a neutron skin whose thickness is sensitive to details of the nuclear force. This links atomic nuclei to properties of neutron stars, thereby relating objects that differ in size by orders of magnitude. The nucleus $^{208}$ Pb is of particular interest because it exhibits a simple structure and is experimentally accessible. However, computing such a heavy nucleus has been out of reach for ab initio theory. By combining advances in quantum many-body methods, statistical tools, and emulator technology, we make quantitative predictions for the properties of $^{208}$ Pb starting from nuclear forces that are consistent with symmetries of low-energy quantum chromodynamics. We explore $1 0^{9}$ different nuclear-force parameterisations via history matching, confront them with data in select light nuclei, and arrive at an importance-weighted ensemble of interactions. We accurately reproduce bulk properties of $^{208}$ Pb and determine the neutron skin thickness, which is smaller and more precise than a recent extraction from parity-violating electron scattering but in agreement with other experimental probes. This work demonstrates how realistic two- and three-nucleon forces act in a heavy nucleus and allows us to make quantitative predictions across the nuclear landscape.
nucl-thastro-ph.HEnucl-exNat.Phys.(2024)·317 citations
05
A transport model study of multiparticle cumulants in $p + p$ collisions at 13 TeV
Xin-Li Zhao🇨🇳 · Zi-Wei Lin🇺🇸 · Liang Zheng🇨🇳 · Guo-Liang Ma🇨🇳
Flow-like signals including the ridge structure observed in small collision systems that are similar to those in large collision systems have led to questions about the onset of collectivity in nuclear collisions. In this study, we use the string melting version of a multi-phase transport (AMPT) model with or without the sub-nucleon geometry for the proton to study multiparticle cumulants in $p + p$ collisions at 13 TeV. Both versions of the model produce negative $c_{2} {4}$ values at high multiplicities. In addition, the dependence of $c_{2} {4}$ on the parton cross section is non-monotonous, where only a range of parton cross section values leads to negative $c_{2} {4}$ . Furthermore, the AMPT model with sub-nucleon geometry better describes the multiplicity dependence of $c_{2} {4}$ , demonstrating the importance of incorporating the sub-nucleon geometry in studies of small collision systems.
nucl-thnucl-exPLB(2023)·21 citations
06
Two-neutron halo structure and anti-halo effect in 31F
Hiroshi Masui · Wataru Horiuchi · Masaaki Kimura
We perform a detailed analysis for the structure of 31F, which is a candidate of the halo nucleus. We calculate the radius and reaction cross-section using a three-body model of 29F+n+n and discuss how the competition between the neutron-pairing and the single-particle energy induces structural changes of 31F. The present analysis further clarifies a new aspect of the anti-halo efect that suppresses the halo structure.
nucl-thFew Body Syst.(2022)·0 citations
07
Ab initio nuclear thermodynamics from lattice effective field theory
Bing-Nan Lu🇨🇳 · Ning Li🇨🇳 · Serdar Elhatisari🇹🇷 · Dean Lee🇺🇸 · Joaquín E. Drut🇺🇸 · Timo A. Lähde🇩🇪 · Evgeny Epelbaum🇩🇪 · Ulf-G. Meißner🇩🇪
We show that the {\it ab initio} calculations of nuclear thermodynamics can be performed efficiently using lattice effective field theory. The simulations use a new approach called the pinhole trace algorithm to calculate thermodynamic observables for a fixed number of protons and neutrons enclosed in a finite box. In this framework, we calculate the equation of state, the liquid-vapor coexistence line and the critical point of neutral symmetric nuclear matter with high precision. Since the algorithm uses a canonical ensemble with a fixed number of particles, it provides a sizable computational advantage over grand canonical ensemble simulations that can be a factor of several thousands to as much as several millions for large volume simulations.
nucl-thcond-mat.stat-mechhep-latnucl-exPoS(2022)·0 citations
08
Recent progress on nucleon form factors
Dalibor Djukanovic🇩🇪
The form factors of the nucleon provide key information on nucleon properties. When confronted with precisely measured observables from experiments, they serve as benchmark quantities for lattice calculations. On the other hand lattice determinations may serve as vital theory input for the interpretation of experiments, e.g. in neutrino-nucleus scattering. I review recent progress in the calculation of nucleon form factors on the lattice and its relevance to future experiments.
↳ hep-lathep-phnucl-thPoS(2022)·11 citations
09
Perturbative and non-perturbative effects in ultraperipheral production of lepton pairs
I.M. Dremin🇷🇺
Perturbative and non-perturbative terms of the cross sections of ultraperipheral production of lepton pairs in ion collisions are taken into account. It is shown that production of low-mass $e^{+} e^{-}$ pairs is strongly enhanced (compared to perturbative estimates) due to the non-perturbative Sommerfeld-Gamow-Sakharov (SGS) factor. Coulomb attraction of the non-relativistic components of those pairs leads to the finite value of their mass distribution at lowest masses. Their annihilation can result in the increased intensity of 511 keV photons. It can be recorded at the NICA collider and is especially crucial in astrophysical implications regarding the 511 keV line emitted from the Galactic center. The analogous effect can be observed in lepton pairs production at LHC. Energy spectra of lepton pairs created in ultraperipheral nuclear collisions and their transverse momenta are calculated.
↳ hep-phastro-ph.HEhep-exnucl-ex+10 citations
10
Gluon-mediated inclusive Deep Inelastic Scattering from Regge to Bjorken kinematics
Renaud Boussarie🇫🇷 · Yacine Mehtar-Tani🇺🇸
We revisit high energy factorization for gluon mediated inclusive Deep Inelastic Scattering (DIS) for which we propose a new semi-classical approach that accounts systematically for the longitudinal extent of the target in contrast with the shockwave limit. In this framework, based on a partial twist expansion, we derive a factorization formula that involves a new gauge invariant unintegrated gluon distribution which depends explicitly on the Feynman $x$ variable. It is shown that both the Regge and Bjorken limits are recovered in this approach. We reproduce in particular the full one loop inclusive DIS cross-section in the leading twist approximation and the all-twist dipole factorization formula in the strict $x = 0$ limit. Although quantum evolution is not discussed explicitly in this work, we argue that the proper treatment of the $x$ dependence of the gluon distribution encompasses the kinematic constraint that must be imposed on the phase-space of gluon fluctuations in the target to ensure stability of small- $x$ evolution.
↳ hep-phnucl-thJHEP(2022)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE