Nuclear Theory·nucl-th

Monday·October 17, 2016

9 papers—2 primary·7 cross-listed

01
Simplified P $_{N}$ Equations for Nonclassical Transport with Isotropic Scattering
R. Vasques · R.N. Slaybaugh
An asymptotic analysis is used to derive a set of diffusion approximations to the nonclassical transport equation with isotropic scattering. These approximations are shown to reduce to the simplified P $_{N}$ equations under the assumption of classical transport, and therefore are labeled nonclassical SP $_{N}$ equations. In addition, the nonclassical SP $_{N}$ equations can be manipulated into a classical form with modified parameters, which can be implemented in existing SP $_{N}$ codes. Numerical results are presented for an one-dimensional random periodic system, validating the theoretical predictions.
nucl-thmath-phmath.MP0 citations
02
Role of core excitation in (d,p) transfer reactions
A. Deltuva · A. Ross · E. Norvaišas · F. M. Nunes
[Background:] Recent work found that core excitation can be important in extracting structure information from (d,p) reactions. [Purpose:] Our objective is to systematically explore the role of core excitation in (d,p) reactions, and understand the origin of the dynamical effects. [Method:] Based on the particle-rotor model of $n +^{10}$ Be, we generate a number of models with a range of separation energies ( $S_{n} = 0.1 - 5.0$ MeV), while maintaining a significant core excited component. We then apply the latest extension of the momentum-space based Faddeev method, including dynamical core excitation in the reaction mechanism to all orders, to the $^{10}$ Be(d,p) $^{11}$ Be like reactions, and study the excitation effects for beam energies from $E_{d} = 15 - 90$ MeV. [Results:] We study the resulting angular distributions and the differences between the spectroscopic factor that would be extracted from the cross sections, when including dynamical core excitation in the reaction, to that of the original structure model. We also explore how different partial waves affect the final cross section. [Conclusions:] Our results show a strong beam energy dependence of the extracted spectroscopic factors that become smaller for intermediate beam energies. This dependence increases for loosely bound systems.
nucl-thnucl-exPRC(2016)·22 citations
03
Complex angular momenta approach for scattering problems in the presence of both monopoles and short range potentials
Fabrizio Canfora🇨🇱
It is analyzed the quantum mechanical scattering off a topological defect (such as a Dirac monopole) as well as a Yukawa-like potential(s) representing the typical effects of strong interactions. This system, due to the presence of a short-range potential, can be analyzed using the powerful technique of the complex angular momenta which, so far, has not been employed in the presence of monopoles (nor of other topological solitons). Due to the fact that spatial spherical symmetry is achieved only up to internal rotations, the partial wave expansion becomes very similar to the Jacob-Wick helicity amplitudes for particles with spin. However, since the angular-momentum operator has an extra "internal" contribution, fixed cuts in the complex angular momentum plane appear. Correspondingly, the background integral in the Regge formula does not decrease for large values of cos(Theta) (namely, large values of the Mandelstam variable s). Hence, the experimental observation of this kind of behavior could be a direct signal of non-trivial topological structures in strong interactions. The possible relations of these results with the soft Pomeron are shortly analyzed.
↳ hep-thhep-phnucl-thPRD(2016)·1 citation
04
Production Uncertainties of p-Nuclei in the $γ$ -Process in Massive Stars Using a Monte Carlo Approach
T. Rauscher · N. Nishimura · R. Hirschi · G. Cescutti · A. St.J. Murphy · A. Heger
Proton-rich nuclei, the so-called p-nuclei, are made in photodisintegration processes in outer shells of massive stars in the course of the final supernova explosion. Nuclear uncertainties in the production of these nuclei have been quantified in a Monte Carlo procedure. Bespoke temperature-dependent uncertainties were assigned to different types of reactions involving nuclei from Fe to Bi and all rates were varied randomly within the uncertainties. The resulting total production uncertainties of the p-nuclei are below a factor of two, with few exceptions. Key reactions dominating the final uncertainties have been identified in an automated procedure using correlations between rate and abundance uncertainties. Our results are compared to those of a previous study manually varying reaction rates.
↳ astro-ph.HEastro-ph.SRnucl-exnucl-thJPS Conf.Proc.(2017)·0 citations
05
Exotic Hadron Bound State Production at Hadronic Colliders
Yi Jin🇨🇳 · Shi-Yuan Li🇨🇳 · Yan-Rui Liu🇨🇳 · Lu Meng🇨🇳 · Zong-Guo Si🇨🇳 · Xiao-Feng Zhang🇨🇳
The non-relativistic wave function framework is applied to study the production and decay of the exotic hadrons which can be effectively described as bound states of other hadrons. Employing the factorized formulation, we investigate the production of exotic hadrons in the multiproduction processes at high energy hadronic colliders with the help of event generators. This study provides crucial information for the measurements of the relevant exotic hadrons.
↳ hep-phnucl-thCPC(2017)·14 citations
06
What can we learn from NJL-type models about dense matter?
Michael Buballa🇩🇪
The merits and limitations of the Nambu--Jona-Lasinio model as a model for strong interactions at nonzero density are critically discussed. We present several examples, demonstrating that, while in general the results should not be trusted quantitatively, the NJL model is a powerful theoretical tool for getting new insights and ideas about the QCD phase diagram and the dense-matter equation of state.
↳ hep-phnucl-thBled Workshops Phys.(2016)·3 citations
07
$η$ bound state: theory and experiment
Hartmut Machner🇩🇪
The search for a quasi bound $η$ meson in atomic nuclei is reviewed. This tentative state is studied theoretically as well as experimentally.
↳ nucl-exhep-phnucl-thEPJ Web Conf.(2017)·1 citation
08
Heavy-Quark QCD Exotica
Richard F. Lebed🇺🇸 · Ryan E. Mitchell🇺🇸 · Eric S. Swanson🇺🇸
This review presents an overview of the remarkable progress in the field of heavy-quark exotic hadrons over the past 15 years. It seeks to be pedagogical rather than exhaustive, summarizing both the progress and specific results of experimental discoveries, and the variety of theoretical approaches designed to explain these new states.
↳ hep-phhep-exnucl-exnucl-thPPNP(2017)·847 citations
09
Proton-proton fusion and tritium $β$ -decay from lattice quantum chromodynamics
Martin J. Savage🇺🇸 · Phiala E. Shanahan🇺🇸 · Brian C. Tiburzi🇺🇸 · Michael L. Wagman🇺🇸 · Frank Winter🇺🇸 · Silas R. Beane🇺🇸 · Emmanuel Chang🇺🇸 · Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸
The nuclear matrix element determining the $pp \to d e^{+} ν$ fusion cross section and the Gamow-Teller matrix element contributing to tritium $β$ -decay are calculated with lattice Quantum Chromodynamics (QCD) for the first time. Using a new implementation of the background field method, these quantities are calculated at the SU(3)-flavor-symmetric value of the quark masses, corresponding to a pion mass of $m_{π}$ ~ 806 MeV. The Gamow-Teller matrix element in tritium is found to be 0.979(03)(10) at these quark masses, which is within $2 σ$ of the experimental value. Assuming that the short-distance correlated two-nucleon contributions to the matrix element (meson-exchange currents) depend only mildly on the quark masses, as seen for the analogous magnetic interactions, the calculated $pp \to d e^{+} ν$ transition matrix element leads to a fusion cross section at the physical quark masses that is consistent with its currently accepted value. Moreover, the leading two-nucleon axial counterterm of pionless effective field theory is determined to be $L_{1, A} = 3.9 (0.1) (1.0) (0.3) (0.9) fm^{3}$ at a renormalization scale set by the physical pion mass, also in agreement with the accepted phenomenological range. This work concretely demonstrates that weak transition amplitudes in few-nucleon systems can be studied directly from the fundamental quark and gluon degrees of freedom and opens the way for subsequent investigations of many important quantities in nuclear physics.
↳ hep-lathep-phnucl-thPRL(2017)·115 citations

Affiliations

first authorsco-authorsvia INSPIRE