Nuclear Theory·nucl-th

Thursday·April 7, 2016

11 papers—7 primary·4 cross-listed

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

Evolving images of the proton: Hadron physics over the past 40 years

Role of Y(4630) in the ppˉ​→Λc​Λˉc​ reaction near threshold

Constraining the supersaturation density equation of state from core-collapse supernova simulations - Excluded volume extension of the baryons

The effect of 22Ne diffusion in the evolution and pulsational properties of white dwarfs with solar metallicity progenitors

Affiliations

Role of $Y (4630)$ in the $p p ˉ \to Λ_{c} Λ ˉ_{c}$ reaction near threshold

The effect of $^{22}$ Ne diffusion in the evolution and pulsational properties of white dwarfs with solar metallicity progenitors