Nuclear Theory·nucl-th

Thursday·October 22, 2015

10 papers—5 primary·5 cross-listed

01
Jacobi no-core shell model for p-shell nuclei
S. Liebig · U.-G. Meißner · A. Nogga
We introduce an algorithm to obtain coefficients of fractional parentage for light $p$ -shell nuclei. The coefficients enable to use Jacobi coordinates in no-core shell model calculations separating off the center-of-mass motion. Fully antisymmetrized basis states are given together with recoupling coefficients that allow one to apply two- and three-nucleon operators. As an example, we study the dependence on the harmonic oscillator frequency of $^{3}$ H, $^{4}$ He, $^{6}$ He, $^{6}$ Li and $^{7}$ Li and extract their binding and excitation energies. The coefficients will be made openly accessible as HDF5 data files.
nucl-thEPJA(2016)·34 citations
02
Hyperon-mixed neutron star with universal many-body repulsion
Y. Yamamoto🇯🇵 · T. Furumoto🇯🇵 · N. Yasutake🇯🇵 · Th.A. Rijken🇳🇱
Neutron stars with large masses $\sim 2 M_{⊙}$ require the hard stiffness of equation of state (EoS) of neutron-star matter. On the other hand, hyperon mixing brings about remarkable softening of EoS. In order to solve this problem, a multi-pomeron exchange potential (MPP) is introduced as a model for the universal many-body repulsion in baryonic systems on the basis of the Extended Soft Core (ESC) baryon-baryon interaction. The strength of MPP is determined by analyzing the nucleus-nucleus scattering with the G-matrix folding model. The interactions in $Λ N$ , $Σ N$ and $Ξ N$ channels are shown to be consistent with experimental indications. The EoS in neutron-star matter with hyperon mixing is obtained from ESC in addition of MPP, and mass-radius relations of neutron stars are derived. The maximum mass is shown to reach $2 M_{⊙}$ even in the case of including hyperon mixing on the basis of model-parameters determined by terrestrial experiments.
nucl-thastro-ph.SREPJA(2016)·50 citations
03
Do hyperons exist in the interior of neutron stars ?
Debarati Chatterjee🇫🇷 · Isaac Vidana🇵🇹
In this work we review the role of hyperons on the properties of neutron and proto-neutron stars. In particular, we revise the so-called "hyperon puzzle", go over some of the solutions proposed to tackle it, and discuss the implications that the recent measurements of unusually high neutron star masses have on our present knowledge of hypernuclear physics. We reexamine also the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.
nucl-thastro-ph.HEEPJA(2016)·277 citations
04
Phenomenological analysis of near threshold periodic modulations of the proton timelike form factor
A. Bianconi🇮🇹 · E. Tomasi-Gustafsson🇫🇷
We have recently highlighted the presence of a periodically oscillating 10 \% modulation in the BABAR data on the proton timelike form factors, in the reaction $e^{+} + e^{-}$ $\to$ $p ˉ + p$ . Here we deepen our previous data analysis, and confirm that in the case of several standard parametrizations it is possible to write the form factor in the form $F_{0}$ $+$ $F_{osc}$ , where $F_{0}$ is a parametrization expressing the long-range trend of the form factor (for $q^{2}$ ranging from the $p ˉ p$ threshold to 36 GeV $^{2}$ ), and $F_{osc}$ is a function of the form $exp (- B p) cos (C p)$ , where $p$ is the relative momentum of the final $p ˉ p$ pair. Error bars allow for a clean identification of the main features of this modulation for $q^{2}$ $<$ 10 GeV $^{2}$ . Assuming this oscillatory modulation to be an effect of final state interactions between the forming proton and the antiproton, we propose a phenomenological model based on a double-layer imaginary optical potential. This potential is flux-absorbing when the distance between the proton and antiproton centers of mass is $≳$ 1.7-1.8 fm and flux-generating when it is $≲$ 1.7-1.8 fm. The main features of the oscillations may be reproduced with some freedom in the potential parameters, but the transition between the two layers must be sudden (0-0.2 fm) to get the correct oscillation period. The flux-absorbing part of the $p ˉ p$ interaction is due to the annihilation of $p ˉ p$ pairs into multi-meson states. We interpret the flux-creating part of the potential as due to the creation of a $1/ q$ -ranged state when the virtual photon decays into a set of current quarks and antiquarks, including heavy ones, that may exist for a short time. The decay of these large mass states leads to an intermediate stage regeneration of the $p ˉ p$ channel.
nucl-thhep-phPRC(2016)·52 citations
05
A MUSTA-FORCE algorithm for solving partial differential equations of relativistic hydrodynamics
J. Porter-Sobieraj · M. Słodkowski · D. Kikoła · J. Sikorski · P. Aszklar
Understanding event-by-event correlations and fluctuations is crucial for the comprehension of the dynamics of heavy ion collisions. Relativistic hydrodynamics is an elegant tool for modeling these phenomena; however, such simulations are time-consuming, and conventional CPU calculations are not suitable for event-by-event calculations. This work presents a feasibility study of a new hydrodynamic code that employs graphics processing units together with a general MUSTA-FORCE algorithm (Multi-Stage Riemann Algorithm - First Order Centered scheme) to deliver a high-performance yet universal tool for event-by-event hydrodynamic simulations. We also investigate the performance of selected slope limiters that reduce the amount of numeric oscillations and diffusion in the presence of strong discontinuities and shock waves. The numerical results are compared to the exact solutions to assess the code's accuracy.
physics.comp-phnucl-thInt.J.Nonlin.Sci.Numer.Simul.(2017)·1 citation
06
Roy-Steiner-equation analysis of pion-nucleon scattering
Martin Hoferichter🇺🇸 · Jacobo Ruiz de Elvira🇩🇪 · Bastian Kubis🇩🇪 · Ulf-G. Meißner🇩🇪
We review the structure of Roy-Steiner equations for pion-nucleon scattering, the solution for the partial waves of the t-channel process $π π \to N ˉ N$ , as well as the high-accuracy extraction of the pion-nucleon S-wave scattering lengths from data on pionic hydrogen and deuterium. We then proceed to construct solutions for the lowest partial waves of the s-channel process $π N \to π N$ and demonstrate that accurate solutions can be found if the scattering lengths are imposed as constraints. Detailed error estimates of all input quantities in the solution procedure are performed and explicit parameterizations for the resulting low-energy phase shifts as well as results for subthreshold parameters and higher threshold parameters are presented. Furthermore, we discuss the extraction of the pion-nucleon $σ$ -term via the Cheng-Dashen low-energy theorem, including the role of isospin-breaking corrections, to obtain a precision determination consistent with all constraints from analyticity, unitarity, crossing symmetry, and pionic-atom data. We perform the matching to chiral perturbation theory in the subthreshold region and detail the consequences for the chiral convergence of the threshold parameters and the nucleon mass.
↳ hep-phhep-latnucl-exnucl-thPhys.Rept.(2016)·324 citations
07
Measurement of the absolute differential cross section of proton-proton elastic scattering at small angles
D. Mchedlishvili🇬🇪 · D. Chiladze🇬🇪 · S. Dymov🇷🇺 · Z. Bagdasarian🇬🇪 · S. Barsov🇷🇺 · R. Gebel🇩🇪 · B. Gou🇨🇳 · M. Hartmann🇩🇪 · A. Kacharava🇩🇪 · I. Keshelashvili🇩🇪 · A. Khoukaz🇩🇪 · P. Kulessa🇵🇱 and 29 other authors
The differential cross section for proton-proton elastic scattering has been measured at a beam energy of 1.0 GeV and in 200 MeV steps from 1.6 to 2.8 GeV for centre-of-mass angles in the range from 12-16 degrees to 25-30 degrees, depending on the energy. Absolute normalisations of typically 3% were achieved by studying the energy losses of the circulating beam of the COSY storage ring as it passed repeatedly through the windowless hydrogen target of the ANKE magnetic spectrometer. It is shown that the data have a significant impact upon a partial wave analysis. After extrapolating the differential cross sections to the forward direction, the results are broadly compatible with the predictions of forward dispersion relations.
↳ nucl-exnucl-thPLB(2016)·8 citations
08
Etaprime interactions with nucleons and nuclei
Steven D. Bass🇦🇹 · Pawel Moskal🇵🇱
We summarise recent progress in theory and experiment towards understanding etaprime meson interactions with nucleons and nuclei. Highlights include the production mechanism of etaprime mesons in proton-proton collisions close to threshold, the etaprime effective mass shift in nuclei and the determination of the etaprime-nucleon scattering length in free space.
↳ hep-phnucl-exnucl-thActa Phys.Polon.B(2016)·11 citations
09
Watson's theorem and the $N Δ (1232)$ axial transition
L. Alvarez-Ruso🇪🇸 · E. Hernández🇪🇸 · J. Nieves🇪🇸 · M.J. Vicente Vacas🇪🇸
We present a new determination of the $N Δ$ axial form factors from neutrino induced pion production data. For this purpose, the model of Hernandez {\it et al.} [Phys. Rev. D76, 033005 (2007)] is improved by partially restoring unitarity. This is accomplished by imposing Watson's theorem on the dominant vector and axial multipoles. As a consequence, a larger $C_{5}^{A} (0)$ , in good agreement with the prediction from the off-diagonal Goldberger-Treiman relation, is now obtained.
↳ hep-phhep-exnucl-exnucl-thPRD(2016)·54 citations
10
Neutral hidden charm pentaquark states $P_{c}^{0} (4380)$ and $P_{c}^{0} (4450)$ in $π^{-} p \to J / ψ n$ reaction
Qi-Fang Lü🇨🇳 · Xiao-Yun Wang🇨🇳 · Ju-Jun Xie🇨🇳 · Xu-Rong Chen🇨🇳 · Yu-Bing Dong🇨🇳
We investigate the neutral hidden charm pentaquark states $P_{c}^{0} (4380)$ and $P_{c}^{0} (4450)$ in $π^{-} p \to J / ψ n$ reaction within an effective Lagrangian approach. The background contributions for the process mainly come from $t$ -channel $π$ and $ρ$ meson exchanges. The contributions of $P_{c}^{0} (4380)$ and $P_{c}^{0} (4450)$ states give clear peak structures in the magnitude of 1 $μ$ b at center of mass energy 4.38 GeV and 4.45 GeV in the total cross sections. Hence, this reaction may provide a new good platform to search for neutral $P_{c}$ states. It is expected that our estimated total cross sections together with the angular distributions can be tested by future experiments at J-PARC.
↳ hep-phhep-exnucl-thPRD(2016)·51 citations

Affiliations

first authorsco-authorsvia INSPIRE