Nuclear Theory·nucl-th

Tuesday·August 23, 2016

8 papers—4 primary·4 cross-listed

01
Shell Model States in the Continuum
A. M. Shirokov · A. I. Mazur · I. A. Mazur · J. P. Vary
We suggest a method for calculating scattering phase shifts and energies and widths of resonances which utilizes only eigenenergies obtained in variational calculations with oscillator basis and their dependence on oscillator basis spacing $ℏΩ$ . We make use of simple expressions for the $S$ -matrix at eigenstates of a finite (truncated) Hamiltonian matrix in the oscillator basis obtained in the HORSE ( $J$ -matrix) formalism of quantum scattering theory. The validity of the suggested approach is verified in calculations with model Woods--Saxon potentials and applied to calculations of $n α$ resonances and non-resonant scattering using the no-core shell model.
nucl-thPRC(2016)·54 citations
02
Chiral EFT based nuclear forces: Achievements and challenges
R. Machleidt🇺🇸 · F. Sammarruca
During the past two decades, chiral effective field theory has become a popular tool to derive nuclear forces from first principles. Two-nucleon interactions have been worked out up to sixth order of chiral perturbation theory and three-nucleon forces up to fifth order. Applications of some of these forces have been conducted in nuclear few- and many-body systems---with a certain degree of success. But in spite of these achievements, we are still faced with great challenges. Among them is the issue of a proper uncertainty quantification of predictions obtained when applying these forces in {\it ab initio} calculations of nuclear structure and reactions. A related problem is the order by order convergence of the chiral expansion. We start this review with a pedagogical introduction and then present the current status of the field of chiral nuclear forces. This is followed by a discussion of representative examples for the application of chiral two- and three-body forces in the nuclear many-body system including convergence issues.
nucl-thnucl-exPhys.Scripta(2016)·112 citations
03
The fluctuations of quadrangular flow
Giuliano Giacalone🇫🇷 · Li Yan🇫🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Jean-Yves Ollitrault🇫🇷
The ATLAS Collaboration has measured for the first time the fourth cumulant of quadrangular flow, $v_{4} {4}^{4}$ . Unlike the fourth cumulants of elliptic and triangular flows, it presents a change of sign above 30\% centrality. We show that this change of sign is predicted by event-by-event hydrodynamics. We argue that it results from the combined effects of a nonlinear hydrodynamic response, which couples quadrangular flow to elliptic flow, and elliptic flow fluctuations.
nucl-thhep-phnucl-exJ.Phys.Conf.Ser.(2017)·15 citations
04
Three-body antikaon-nucleon systems
N.V. Shevchenko🇨🇿
The paper contains a review of the exact or accurate results achieved in the field of the three-body antikaon-nucleon physics. Different states and processes in $K ˉ N N$ and $K ˉ K ˉ N$ systems are considered. In particular, quasi-bound states in $K^{-} pp$ and $K^{-} K^{-} p$ systems were investigated together with antikaonic deuterium atom. Near-threshold scattering of antikaons on deuteron, including the $K^{-} d$ scattering length, and applications of the scattering amplitudes are also discussed. All exact three-body results were calculated using some form of Faddeev equations. Different versions of $K ˉ N$ , $Σ N$ , $K ˉ K ˉ$ , and $N N$ potentials, specially constructed for the calculations, allowed investigation of the dependence of the three-body results on the two-body input. Special attention is paid to the antikaon-nucleon interaction, being the most important for the three-body systems. Approximate calculations, performed additionally to the exact ones, demonstrate accuracy of the commonly used approaches.
nucl-thFew Body Syst.(2017)·25 citations
05
The magnetic moments and electromagnetic form factors of the decuplet baryons in chiral perturbation theory
Hao-Song Li🇨🇳 · Zhan-Wei Liu🇦🇺 · Xiao-Lin Chen🇨🇳 · Wei-Zhen Deng🇨🇳 · Shi-Lin Zhu🇨🇳
We have systematically investigated the magnetic moments and magnetic form factors of the decuplet baryons to the next-to-next-leading order in the framework of the heavy baryon chiral perturbation theory. Our calculation includes the contributions from both the intermediate decuplet and octet baryon states in the loops. We also calculate the charge and magnetic dipole form factors of the decuplet baryons. Our results may be useful to the chiral extrapolation of the lattice simulations of the decuplet electromagnetic properties.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2017)·22 citations
06
The LPM effect in sequential bremsstrahlung: 4-gluon vertices
Peter Arnold🇺🇸 · Han-Chih Chang🇺🇸 · Shahin Iqbal🇵🇰
The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper, we continue study of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-gluon approximations. In particular, this paper completes the calculation of the rate for real double gluon bremsstrahlung from an initial gluon with various simplifying assumptions (thick media; $q^$ approximation; and large $N_{c}$ ) by now including processes involving 4-gluon vertices.
↳ hep-phnucl-thJHEP(2016)·29 citations
07
Bayesian Estimation of Thermonuclear Reaction Rates
Christian Iliadis🇺🇸 · Kevin Anderson🇺🇸 · Alain Coc🇫🇷 · Frank Timmes🇺🇸 · Sumner Starrfield🇺🇸
The problem of estimating non-resonant astrophysical S-factors and thermonuclear reaction rates, based on measured nuclear cross sections, is of major interest for nuclear energy generation, neutrino physics, and element synthesis. Many different methods have been applied in the past to this problem, almost all of them based on traditional statistics. Bayesian methods, on the other hand, are now in widespread use in the physical sciences. In astronomy, for example, Bayesian statistics is applied to the observation of extra-solar planets, gravitational waves, and type Ia supernovae. However, nuclear physics, in particular, has been slow to adopt Bayesian methods. We present astrophysical S-factors and reaction rates based on Bayesian statistics. We develop a framework that incorporates robust parameter estimation, systematic effects, and non-Gaussian uncertainties in a consistent manner. The method is applied to the d(p, $γ$ ) $^{3}$ He, $^{3}$ He( $^{3}$ He,2p) $^{4}$ He, and $^{3}$ He( $α$ , $γ$ ) $^{7}$ Be reactions, important for deuterium burning, solar neutrinos, and big bang nucleosynthesis.
↳ astro-ph.SRnucl-thApJ(2016)·64 citations
08
Quark self-energy in an ellipsoidally anisotropic quark-gluon plasma
Babak S. Kasmaei🇺🇸 · Mohammad Nopoush🇺🇸 · Michael Strickland🇺🇸
We calculate the quark self-energy in a quark-gluon plasma that possesses an ellipsoidal momentum-space anisotropy in the local rest frame. By introducing additional transverse momentum anisotropy parameters into the parton distribution functions, we generalize previous results which were obtained for the case of a spheroidal anisotropy. Our results demonstrate that the presence of anisotropies in the transverse directions affects the real and imaginary parts of quark self-energy and, consequently, the self-energy depends on both the polar and azimuthal angles in the local rest frame of the matter. Our results for the quark self-energy set the stage for the calculation of the effects of ellipsoidal momentum-space anisotropy on quark-gluon plasma photon spectra and collective flow.
↳ hep-phnucl-thPRD(2016)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE