Nuclear Theory·nucl-th

Thursday·April 7, 2016

11 papers—7 primary·4 cross-listed

01
Time-reversal-invariance-violating nucleon-nucleon potential in the 1/N_c expansion
Daris Samart🇹🇭 · Carlos Schat🇦🇷 · Matthias R. Schindler🇺🇸 · Daniel R. Phillips🇺🇸
We apply the large- $N_{c}$ expansion to the time-reversal-invariance-violating (TV) nucleon-nucleon potential. The operator structures contributing to next-to-next-to-leading order in the large- $N_{c}$ counting are constructed. For the TV and parity-violating case we find a single operator structure at leading order. The TV but parity-conserving potential contains two leading-order terms, which however are suppressed by 1/ $N_{c}$ compared to the parity-violating potential. Comparison with phenomenological potentials, including the chiral EFT potential in the TV parity-violating case, leads to large- $N_{c}$ scaling relations for TV meson-nucleon and nucleon-nucleon couplings.
nucl-thhep-phnucl-exPRC(2016)·19 citations
02
Monopole transitions to cluster states in $^{10}$ Be and $^{9}$ Li
Yoshiko Kanada-En'yo
Isoscalar monopole transitions from the ground states to cluster states in $\Be$ and $\Li$ are investigated with $\He + α$ and $\He + t$ cluster models, respectively. In $\Be$ , significant monopole strengths to $\He + α$ cluster resonances of $\Be (0_{3, 4}^{+})$ above the $α$ -decay threshold are obtained, whereas those to $\He + t$ cluster resonances in $^{9}$ Li are not enhanced because of the large fragmentation of the strengths in the corresponding energy region. The monopole transition to $\Be (0_{2}^{+})$ having the molecular orbital structure is relatively weak compared with those to $\He + α$ cluster resonances. Monopole strength distributions do not directly correspond to distributions of $\He (0^{+}) + α$ and $\He (0 +) + t$ components but they reflect component of the deformed $\He$ cluster with a specific orientation, which is originally embedded in the ground state.
nucl-thPRC(2016)·17 citations
03
Radii of neutron drops probed via the neutron skin thickness of nuclei
P. W. Zhao · S. Gandolfi
Multi-neutron systems are crucial to understanding the physics of neutron-rich nuclei and neutron stars. Neutron drops, neutrons confined in an external field, are investigated systematically in both non-relativistic and relativistic density functional theories and with ab initio calculations. We demonstrate a strong linear correlation, which is universal in the realm of mean-field models, between the rms radii of neutron drops and the neutron skin thickness of Pb-208 and Ca-48; i.e., the difference between the neutron and proton rms radii of a nucleus. Due to its high quality, this correlation can be used to deduce the radii of neutron drops from the measured neutron skin thickness in a model-independent way, and the radii obtained for neutron drops can provide a useful constraint for realistic three neutron forces. This correlation, together with high- precision measurements of the neutron skin thicknesses of Pb-208 and Ca-48, will have an enduring impact on the understanding of multi-neutron interactions, neutron-rich nuclei, neutron stars, etc.
nucl-thnucl-exPRC(2016)·33 citations
04
Quasi-elastic scattering of 6He, 7Be, and 8B nuclei by 12C nuclei
V. I. Kovalchuk
The observed cross sections of quasi-elastic scattering of 6He, 7Be, and 8B nuclei by 12C nuclei are described within the framework of the diffraction nuclear model and the model of nucleus-nucleus scattering in the high-energy approximation with a double folding potential, for intermediate energies of the incident particles. The calculations make use of realistic distributions of nucleon densities and take account of the Coulomb interaction and inelastic scattering with excitation of low-lying collective states of the target.
nucl-thRuss.Phys.J.(2015)·0 citations
05
The Barcelona-Catania-Paris-Madrid functional with a realistic effective mass
M. Baldo🇮🇹 · L.M. Robledo🇪🇸 · P. Schuck🇫🇷 · X. Viñas🇪🇸
The Barcelona-Catania-Paris-Madrid (BCPM) functional recently proposed to describe nuclear structure properties of finite nuclei is generalized as to include a realistic effective mass. The resulting functional is as good as the previous one in describing binding energies, radii, deformation properties, etc and, in addition, the description of Giant Quadrupole Resonance energies is greatly improved.
nucl-thPRC(2017)·28 citations
06
On the near-threshold incoherent $ϕ$ photoproduction on the deuteron: any trace of a resonance?
Alvin Kiswandhi🇹🇼 · Shin Nan Yang🇹🇼 · Yu Bing Dong🇨🇳
We study the near-threshold incoherent $ϕ$ photoproduction on the deuteron based on a model of $γ N \to ϕN$ , consisting of Pomeron, $(π, η)$ exchanges, and a $J^{P} = 3/ 2^{-}$ resonance, which describes the low energy $γ p \to ϕp$ LEPS data well, including the peak in the forward differential cross section. The calculation is done up to double rescatterings, with the spin dependence of the elementary $γ N \to ϕN$ amplitude retained throughout the calculation. The Fermi motion and final-state interactions (FSI) are all properly treated as prescribed by realistic nucleon-nucleon interaction. The couplings of the resonance to $γ n$ and $ϕ n$ channels are estimated with the help of a constituent quark model. The main features of the LEPS and CLAS data are described reasonably well except for some quantitative discrepancies at very low energies and low momentum transfers regions. It is found that contributions of Fermi motion, $p n$ FSI, and resonance are all indispensable in bridging the differences between the single-scattering results and the data. The off-shell rescattering is found to be important as it cancels out a large portion of the on-shell contribution. The discrepancies at low momentum transfer region might be related to the binning size of the data. No peak is found to be associated with the weak resonance as it gets smeared out by the Fermi motion and FSI with deuterium target. The problem at very low energy region hints at the possible contributions from other mechanisms and should be investigated in depth with the use of recent high statistics $γ p \to ϕp$ data from CLAS.
nucl-thPRC(2016)·9 citations
07
Analysis of the intermediate-state contributions to neutrinoless double beta-minus decays
Juhani Hyvärinen🇫🇮 · Jouni Suhonen🇫🇮
A comprehensive analysis of the structure of the nuclear matrix elements (NMEs) of neutrinoless double beta-minus decays to the 0^+ ground and first excited states is performed in terms of the contributing multipole states in the intermediate nuclei of neutrinoless double beta-minus transitions. We concentrate on the transitions mediated by the light (l-NMEs) Majorana neutrinos. As nuclear model we use the proton-neutron quasiparticle random-phase approximation (pnQRPA) with a realistic two-nucleon interaction based on the Bonn one-boson-exchange G matrix. In the computations we include the appropriate short-range correlations, nucleon form factors, higher-order nucleonic weak currents and restore the isospin symmetry by the isoscalar-isovector decomposition of the particle-particle proton-neutron interaction parameter g_{pp}.
nucl-thAdv.High Energy Phys.(2016)·15 citations
08
Evolving images of the proton: Hadron physics over the past 40 years
Michael R. Pennington🇺🇸
Once upon a time, the world was simple: the proton contained three quarks, two {\it ups} and a {\it down}. How these give the proton its mass and its spin seemed obvious. Over the past forty years the proton has become more complicated, and how even these most obvious of its properties is explained in a universe of quarks, antiquarks and gluons remains a challenge. That this should be so should come as no surprise. Quantum Chromodynamics, the theory of the strong interaction, is seemingly simple, and its consequences are straightforward in the domain of hard scattering where perturbation theory applies. However, the beauty of the hadron world is its diversity. The existence of hadrons, their properties, and their binding into nuclei do not appear in the Lagrangian of QCD. They all emerge as a result of its strong coupling. Strong coupling QCD creates complex phenomena, much richer than known 40 years ago: a richness that ensures colour confinement and accounts for more than 95\% of the mass of the visible Universe. How strong coupling QCD really works requires a synergy between experiment and theory. A very personal view of these fascinating developments in cold QCD is presented.
↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2016)·13 citations
09
Role of $Y (4630)$ in the $p p ˉ \to Λ_{c} Λ ˉ_{c}$ reaction near threshold
Yan-Yan Wang🇨🇳 · Qi-Fang Lü🇨🇳 · En Wang🇨🇳 · De-Min li🇨🇳
We investigate the charmed baryon production reaction $p p ˉ \to Λ_{c} Λ ˉ_{c}$ in an effective Lagrangian approach. Besides the $t$ -channel $D^{0}$ and $D^{* 0}$ mesons exchanges, the $s$ -channel $Y (4630)$ meson exchange is taken into account. For the total cross sections, the $D^{0}$ and $D^{* 0}$ mesons provide minor background contributions, while the $Y (4630)$ state gives a clear peak structure with the magnitude of 10 $μ$ b at center of mass energy 4.63 GeV. Basing on the results, we suggest that the reaction of $p p ˉ \to Λ_{c} Λ ˉ_{c}$ can be used to search for the $1^{--}$ charmonium-like $Y (4630)$ state, and our predictions can be tested in future by the $P ˉ ANDA$ facility.
↳ hep-phnucl-thPRD(2016)·17 citations
10
Constraining the supersaturation density equation of state from core-collapse supernova simulations - Excluded volume extension of the baryons
Tobias Fischer
In this article the role of the supersaturation density equation of state (EOS) is explored in simulations of failed core-collapse supernova explosions. Therefore the nuclear EOS is extended via a one-parameter excluded volume description for baryons, taking into account their finite and increasing volume with increasing density in excess of saturation density. Parameters are selected such that the resulting supernova EOS represent extreme cases, with high pressure variations at supersaturation density which feature extreme stiff and soft EOS variants of the reference case, i.e. without excluded volume corrections. Unlike in the interior of neutron stars with central densities in excess of several times saturation density, central densities of core-collapse supernovae reach only slightly above saturation density. Hence, the impact of the supersaturation density EOS on the supernova dynamics as well as the neutrino signal is found to be negligible. It is mainly determined from the low- and intermediate-density domain, which is left unmodified within this generalized excluded volume approach.
↳ astro-ph.HEnucl-thEPJA(2016)·8 citations
11
The effect of $^{22}$ Ne diffusion in the evolution and pulsational properties of white dwarfs with solar metallicity progenitors
María E. Camisassa · Leandro G. Althaus · Alejandro H. Córsico · Núria Vinyoles · Aldo M. Serenelli · Jordi Isern · Marcelo M. Miller Bertolami · Enrique Garcí a--Berro
Because of the large neutron excess of $^{22}$ Ne, this isotope rapidly sediments in the interior of the white dwarfs. This process releases an additional amount of energy, thus delaying the cooling times of the white dwarf. This influences the ages of different stellar populations derived using white dwarf cosmochronology. Furthermore, the overabundance of $^{22}$ Ne in the inner regions of the star, modifies the Brunt-Väisälä frequency, thus altering the pulsational properties of these stars. In this work, we discuss the impact of $^{22}$ Ne sedimentation in white dwarfs resulting from Solar metallicity progenitors ( $Z = 0.02$ ). We performed evolutionary calculations of white dwarfs of masses $0.528$ , $0.576$ , $0.657$ and $0.833$ M $_{\sun}$ , derived from full evolutionary computations of their progenitor stars, starting at the Zero Age Main Sequence all the way through central hydrogen and helium burning, thermally-pulsing AGB and post-AGB phases. Our computations show that at low luminosities ( $lo g (L / L_{\sun}) \la - 4.25$ ), $^{22}$ Ne sedimentation delays the cooling of white dwarfs with Solar metallicity progenitors by about 1~Gyr. Additionally, we studied the consequences of $^{22}$ Ne sedimentation on the pulsational properties of ZZ~Ceti white dwarfs. We find that $^{22}$ Ne sedimentation induces differences in the periods of these stars larger than the present observational uncertainties, particularly in more massive white dwarfs.
↳ astro-ph.SRastro-ph.GAcond-mat.stat-mechnucl-thApJ(2016)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE