Nuclear Theory·nucl-th

Wednesday·August 30, 2017

10 papers—4 primary·6 cross-listed

01
New Results on Short-Range Correlations in Nuclei
Nadia Fomin🇺🇸 · Douglas Higinbotham🇺🇸 · Misak Sargsian🇺🇸 · Patricia Solvignon🇺🇸
Nuclear dynamics at short distances is one of the most fascinating topics of strong interaction physics. The physics of it is closely related to the understanding the role of the QCD in generating nuclear forces at short distances as well as understanding the dynamics of the super-dense cold nuclear matter relevant to the interior of neutron stars. With an emergence of high energy electron and proton beams there is a significant recent progress in high energy nuclear scattering experiments aimed at studies of short-range structure of nuclei. This in turn stimulated new theoretical studies resulting in the observation of several new phenomena specific to the short range structure of nuclei. In this work we review recent theoretical and experimental progress in studies of short-range correlations in nuclei and their importance for advancing our understanding of the dynamics of nuclear interactions at small distances.
nucl-thnucl-exAnn.Rev.Nucl.Part.Sci.(2017)·80 citations
02
Isospin-symmetry breaking in superallowed Fermi beta-decay due to isospin-nonconserving forces
K. Kaneko · Y. Sun · T. Mizusaki · S. Tazaki · S. K. Ghorui
We investigate isospin-symmetry breaking effects in the sd-shell region with large-scale shell-model calculations, aiming to understand the recent anomalies observed in superallowed Fermi beta-decay. We begin with calculations of Coulomb displacement energies (CDE's) and triplet displacement energies (TDE's) by adding the T=1,J=0 isospin nonconserving (INC) interaction into the usual isospin-invariant Hamiltonian. It is found that CDE's and TDE's can be systematically described with high accuracy. A total number of 122 one- and two-proton separation energies are predicted accordingly, and locations of the proton drip-line and candidates for proton-emitters are thereby suggested. However, attempt to explain the anomalies in the superallowed Fermi beta-decay fails because these well-fitted T=1,J=0 INC interactions are found no effects on the nuclear matrix elements. It is demonstrated that the observed large isospin-breaking correction in the 32Cl beta-decay, the large isospin-mixing in the 31Cl beta-decay, and the small isospin-mixing in the 23Al beta-decay can be consistently understood by introducing additional T=1,J=2 INC interactions related to the s1/2 orbit.
nucl-thPLB(2017)·33 citations
03
Analysis of corrections to the eikonal approximation
Chloë Hebborn · Pierre Capel
Various corrections to the eikonal approximations are studied for two- and three-body nuclear collisions with the goal to extend the range of validity of this approximation to beam energies of 10 MeV/nucleon. Wallace's correction does not improve much the elastic-scattering cross sections obtained at the usual eikonal approximation. On the contrary, a semiclassical approximation that substitutes the impact parameter by a complex distance of closest approach computed with the projectile-target optical potential efficiently corrects the eikonal approximation. This opens the possibility to analyze data measured down to 10 MeV/nucleon within eikonal-like reaction models.
nucl-thPRC(2017)·11 citations
04
A Minimal Nuclear Energy Density Functional
Aurel Bulgac🇺🇸 · Michael McNeil Forbes🇺🇸 · Shi Jin🇺🇸 · Rodrigo Navarro Perez🇺🇸 · Nicolas Schunck🇺🇸
We present a minimal nuclear energy density functional (NEDF) called "SeaLL1" that has the smallest number of possible phenomenological parameters to date. SeaLL1 is defined by 7 significant phenomenological parameters, each related to a specific nuclear property. It describes the nuclear masses of even-even nuclei with a mean energy error of 0.97 MeV and a standard deviation 1.46 MeV, two-neutron and two-proton separation energies with r.m.s. errors of 0.69 MeV and 0.59 MeV respectively, and the charge radii of 345 even-even nuclei with a mean error $ϵ_{r} =$ 0.022 fm and a standard deviation $σ_{r} =$ 0.025 fm. SeaLL1 incorporates constraints on the EoS of pure neutron matter from quantum Monte Carlo calculations with chiral effective field theory two-body (NN) interactions at N3LO level and three-body (NNN) interactions at the N2LO level. Two of the seven parameters are related to the saturation density and the energy per particle of the homogeneous symmetric nuclear matter, one is related to the nuclear surface tension, two are related to the symmetry energy and its density dependence, one is related to the strength of the spin-orbit interaction, and one is the coupling constant of the pairing interaction. We identify additional phenomenological parameters that have little effect on ground-state properties, but can be used to fine-tune features such as the Thomas-Reiche-Kuhn sum rule, the excitation energy of the giant dipole and Gamow-Teller resonances, the static dipole electric polarizability, and the neutron skin thickness.
nucl-thPRC(2018)·80 citations
05
Nucleon Axial Radius and Muonic Hydrogen - A New Analysis and Review
Richard J. Hill🇺🇸 · Peter Kammel🇺🇸 · William J. Marciano🇺🇸 · Alberto Sirlin🇺🇸
Weak capture in muonic hydrogen ( $μ$ H) as a probe of the chiral properties and nucleon structure predictions of Quantum Chromodynamics (QCD) is reviewed. A recent determination of the axial-vector charge radius squared, $r_{A}^{2} (z exp.) = 0.46 (22) fm^{2}$ , from a model independent $z$ expansion analysis of neutrino-nucleon scattering data is employed in conjunction with the MuCap measurement of the singlet muonic hydrogen capture rate, $Λ_{singlet}^{MuCap} = 715.6 (7.4) s^{- 1}$ , to update the induced pseudoscalar nucleon coupling: $g ˉ_{P}^{MuCap} = 8.23 (83)$ derived from experiment, and $g ˉ_{P}^{theory} = 8.25 (25)$ predicted by chiral perturbation theory. Accounting for correlated errors this implies $g ˉ_{P}^{theory} / g ˉ_{P}^{MuCap} = 1.00 (8)$ , confirming theory at the 8% level. If instead, the predicted expression for $g ˉ_{P}^{theory}$ is employed as input, then the capture rate alone determines $r_{A}^{2} (μ H) = 0.46 (24) fm^{2}$ , or together with the independent $z$ expansion neutrino scattering results, a weighted average $r_{A}^{2} (ave.) = 0.46 (16) fm^{2}$ . Sources of theoretical uncertainty are critically examined and potential experimental improvements are described that can reduce the capture rate error by about a factor of 3. Muonic hydrogen can thus provide a precise and independent $r_{A}^{2}$ value which may be compared with other determinations, such as ongoing lattice gauge theory calculations. The importance of an improved $r_{A}^{2}$ determination for phenomenology is illustrated by considering the impact on critical neutrino-nucleus cross sections at neutrino oscillation experiments.
↳ hep-phhep-latnucl-exnucl-thRept.Prog.Phys.(2018)·85 citations
06
Determination of electric dipole transitions in heavy quarkonia using potential non-relativistic QCD
Jorge Segovia🇩🇪 · Sebastian Steinbeißer🇩🇪
The electric dipole transitions $χ_{b J} (1 P) \to γ Υ (1 S)$ with $J = 0, 1, 2$ and $h_{b} (1 P) \to γ η_{b} (1 S)$ are computed using the weak-coupling version of a low-energy effective field theory named potential non-relativistic QCD (pNRQCD). In order to improve convergence and thus give firm predictions for the studied reactions, the full static potential is incorporated into the leading order Hamiltonian; moreover, we must handle properly renormalon effects and re-summation of large logarithms. The precision we reach is $k_{γ}^{3} / (m v)^{2} \times O (v^{2})$ , where $k_{γ}$ is the photon energy, $m$ is the mass of the heavy quark and $v$ its velocity. Our analysis separates those relativistic contributions that account for the electromagnetic interaction terms in the pNRQCD Lagrangian which are $v^{2}$ suppressed and those that account for wave function corrections of relative order $v^{2}$ . Among the last ones, corrections from $1/ m$ and $1/ m^{2}$ potentials are computed, but not those coming from higher Fock states since they demand non-perturbative input and are $Λ_{QCD}^{2} / (m v)^{2}$ or $Λ_{QCD}^{3} / (m^{3} v^{4})$ suppressed, at least, in the strict weak coupling regime. These proceedings are based on the forthcoming publication \cite{steinbeisser}
↳ hep-phhep-exhep-latnucl-thJ.Phys.Conf.Ser.(2018)·1 citation
07
Linearly polarized gluons and axial charge fluctuations in the Glasma
T. Lappi🇫🇮 · S. Schlichting🇺🇸
We calculate of the one- and two-point correlation functions of the energy density and the divergence of the Chern-Simons current in the nonequilibrium Glasma state formed in a high-energy nuclear collision. We show that the latter depends on the difference of the total and linearly polarized gluon transverse momentum distributions. Since the divergence of the Chern-Simons current provides the source of axial charge, we infer information about the statistical properties of axial charge production at early times. We further develop a simple phenomenological model to characterize axial charge distributions in terms of distributions of the energy density.
↳ hep-phnucl-thPRD(2018)·68 citations
08
The Equation of State for the Nucleonic and Hyperonic Core of Neutron Stars
Laura Tolos🇪🇸 · Mario Centelles🇪🇸 · Angels Ramos🇪🇸
We reexamine the equation of state for the nucleonic and hyperonic inner core of neutron stars that satisfies the 2 $M_{⊙}$ observations as well as the recent determinations of stellar radii below 13 km, while fulfilling the saturation properties of nuclear matter and finite nuclei together with the constraints on the high-density nuclear pressure coming from heavy-ion collisions. The recent nucleonic FSU2R and hyperonic FSU2H models are fine tuned improving the density dependence of pure neutron matter at subsaturation densities. The corresponding nuclear matter properties at saturation, the symmetry energy and its slope turn out to be compatible with recent experimental and theoretical determinations. We obtain the mass, radius and composition of neutron stars for the two updated models and study the impact on these properties of the uncertainties in the hyperon-nucleon couplings estimated from hypernuclear data. We find that the onset of appearance of each hyperon strongly depends on the hyperon-nuclear uncertainties, whereas the maximum masses for neutron stars differ by at most 0.1 $M_{⊙}$ , although a larger deviation should be expected tied to the lack of knowledge of the hyperon potentials at the high densities present in the center of $2 M_{⊙}$ stars. For easier use, we provide tables with the results from the FSU2R and FSU2H models for the equation of state and the neutron star mass-radius relation.
↳ astro-ph.HEnucl-thPubl.Astron.Soc.Austral.·113 citations
09
Isothermal compressibility of hadronic matter formed in relativistic nuclear collisions
Maitreyee Mukherjee🇮🇳 · Sumit Basu🇺🇸 · Arghya Chatterjee🇮🇳 · Sandeep Chatterjee🇵🇱 · Souvik Priyam Adhya🇮🇳 · Sanchari Thakur🇮🇳 · Tapan K. Nayak🇮🇳
We present the first estimates of isothermal compressibility (\kT) of hadronic matter formed in relativistic nuclear collisions ( $s_{NN} = 7.7$ GeV to 2.76~TeV) using experimentally observed quantities. \kT~is related to the fluctuation in particle multiplicity, temperature, and volume of the system formed in the collisions. Multiplicity fluctuations are obtained from the event-by-event distributions of charged particle multiplicities in narrow centrality bins. The dynamical components of the fluctuations are extracted by removing the contributions to the fluctuations from the number of participating nucleons. From the available experimental data, a constant value of \kT~has been observed as a function of collision energy. The results are compared with calculations from UrQMD, AMPT, and EPOS event generators, and estimations of \kT~are made for Pb-Pb collisions at the CERN Large Hadron Collider. A hadron resonance gas (HRG) model has been used to calculate \kT~as a function of collision energy. Our results show a decrease in \kT~at low collision energies to \sNN~ $\sim$ ~20~GeV, beyond which the \kT~values remain almost constant.
↳ nucl-exhep-exhep-phnucl-thPLB(2018)·23 citations
10
Heavy and heavy-light mesons and the Lorentz structure of the quark-antiquark interaction
Sofia Leitão🇵🇹 · Alfred Stadler🇵🇹 · M. T. Peña🇵🇹 · Elmar P. Biernat🇵🇹
We solve a Minkowski-space integral equation, derived in the Covariant Spectator Theory, for quark-antiquark bound states describing heavy and heavy-light mesons. The equation's kernel contains a one-gluon exchange interaction and a covariant generalization of a linear confining potential with a mixed scalar, pseudoscalar, and vector Lorentz structure, characterized by a continuous mixing parameter. We investigate to what extent the Lorentz structure of the confining kernel can be determined by fitting the mixing parameter to the meson spectrum.
↳ hep-phnucl-thActa Phys.Polon.Supp.(2017)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE