Neutrino self-interaction and MSW effects on the supernova neutrino-process

We calculate the abundances of $^{7}$Li, $^{11}$B, $^{92}$Nb, $^{98}$Tc, $^{138}$La, and $^{180}$Ta produced by neutrino $(\nu)$ induced reactions in a core-collapse supernova explosion. We consider the modification by $\nu$ self-interaction ($\nu$-SI) near the neutrinosphere and the Mikheyev-Smirnov-Wolfenstein effect in outer layers for time-dependent neutrino energy spectra. Abundances of $^{7}$Li and heavy isotopes $^{92}$Nb, $^{98}$Tc and $^{138}$La are reduced by a factor of 1.5-2.0 by the $\nu$-SI. In contrast, $^{11}$B is relatively insensitive to the $\nu$-SI. We find that the abundance ratio of heavy to light nucleus, $^{138}$La/$^{11}$B, is sensitive to the neutrino mass hierarchy, and the normal mass hierarchy is more likely to be consistent with the solar abundances

Comprehensive Analyses of the Neutrino-Process in the Core-collapsing Supernova

We investigate the neutrino flavor change effects due to neutrino self-interaction, shock wave propagation as well as matter effect on the neutrino process of the core-collapsing supernova. For the hydrodynamics, we use two models: a simple thermal bomb model and a specified hydrodynamic model for SN1987A. As a pre-supernova model, we take an updated model adjusted to explain the SN1987A employing recent development of the $(n,\gamma)$ reaction rates for nuclei near the stability line $(A \sim 100)$. As for the neutrino luminosity, we adopt two different models: equivalent neutrino luminosity and non-equivalent luminosity models. The latter is taken from the synthetic analyses of the CCSN simulation data which involved quantitatively the results obtained by various neutrino transport models. Relevant neutrino-induced reaction rates are calculated by a shell model for light nuclei and a quasi-particle random phase approximation model for heavy nuclei. For each model, we present abundances of the light nuclei ($^7$Li, $^7$Be, $^{11}$B and $^{11}$C) and heavy nuclei ($^{92}$Nb, $^{98}$Tc, $^{138}$La and $^{180}$Ta) produced by the neutrino-process. The light nuclei abundances turn out to be sensitive to the Mikheyev-Smirnov-Wolfenstein region around ONeMg region while the heavy nuclei are mainly produced prior to the MSW region. Through the detailed analyses of the numerical abundances, we find that neutrino self-interaction becomes a key ingredient in addition to the MSW effect for understanding the neutrino process and the relevant nuclear abundances. However, the whole results are shown to depend on the adopted neutrino luminosity scheme. Detailed evaluations of the nuclear abundances for the two possible neutrino mass hierarchies are performed with the comparison to the available meteorite analyses data. The normal mass hierarchy is shown to be more compatible with the meteoritic data

Production of light elements and 98Tc through the ?? -process with the neutrino oscillation in supernova explosion

Stars ending with core collapse supernovae (SNe) emit a tremendous number of neutrinos during their explosions. While these neutrinos pass through each layer of the stars, they react with the nuclides in the progenitor. Although the neutrino cross sections are very small, its huge flux is high enough to react with nuclides to change their abundances. We consider this ??-process, by which abundances of some elements may be explained exclusively by this neutrino process. One of the candidates is 98Tc. In this study, we check the ??-process contributions due to the neutrino reactions. In this calculation we also include the neutrino oscillation effect in the matter with varying density, so called MSW effect, not only for 98Tc production but also 4He and 12C destruction, which occurs at first in the He/C layer in the present model

Reinvestigating the Gamow Factor of Reactions on Light Nuclei

We present a modified Gamow factor by reinvestigating the conventional assumptions used in its derivation. The conventional Gamow factor, factorized from the total cross section, effectively describes the penetration probabilities (PPs) in low-energy nuclear reactions under the assumption of particle energies significantly lower than the Coulomb barrier. However, we find that the assumption is invalid for light nuclei, resulting in PPs that depend on the nuclear potential depth for such nuclei. By adopting a potential depth fitted to experimental fusion cross sections, we demonstrate that PPs for light nuclei (D+D, D+T, D+ ^3 He, p+D, p+ ^6 Li, and p+ ^7 Li) become higher than those predicted by the conventional form near the Coulomb barrier. This reduces the Gamow peak energy by a factor of 5.3 maximally compared to the conventional form. Furthermore, we show that the enhancement factor due to the Debye screening effects in the solar core can be reduced by approximately 5%–10% due to the modified PP. Our findings hold implications for evaluating the available energy region in low-energy reaction experiments based on the Gamow peak energy region and for understanding electron screening effects in typical astrophysical environments

Neutrino self-interaction and MSW eects by an equi-partitioned Fermi-Dirac neutrino luminosity on the supernova neutrino-process

We investigate nuclear abundances produced from the neutrino neutrino-process in supernova explosions. By adopting an equi-partitioned neutrino-luminosity for each neutrino flavor, we have calculated the neutrino-flux propagation including both its modification by neutrino self-interaction (neutrino-SI) near the neutrino-sphere and the Mikheyev-Smirnov-Wolfenstein (MSW) effect in the outer O-Ne-Mg layer. The abundances of heavierisotopes 92Nb, 98Tc and 138La are largely enhanced by the neutrino-SI for the inverted mass hierarchy. The ratio of 7Li/11B is lower in the inverted hierarchy than in the normal hierarchy

Impact of hypernova p-process nucleosynthesis on the galactic chemical evolution of Mo and Ru

We calculate Galactic Chemical Evolution (GCE) of Mo and Ru by taking into account the contribution from neutrino p-process nucleosynthesis. We estimate yields of p-nuclei such as 92;94Mo and 96;98Ru through the neutrino p-process in various supernova (SN) progenitors based upon recent models. In particular,the neutrino p-process in energetic hypernovae produces a large amount of p-nuclei compared to the yield in ordinary core-collapse SNe. We find that the neutrino p-process in hypernovae is the main contributor to the elemental abundance of 92Mo at low metallicity [Fe/H] < 2. Our theoretical prediction of the elemental abundances in metal-poor stars becomes more consistent with observational data when the neutrino p-process in hypernovae is taken into account

Nuclear cosmochronometers for supernova neutrino-process

The short-lived unstable isotopes with half-lives of 0.1–10 My have been used as nuclear cosmochronometers to evaluate from an astrophysical event such as supernova (SN) explosion or AGB s-process to the solar system formation. We have proposed shorted-lived radioisotopes of 92Nb and 98Tc as the nuclear cosmochronometers for supernova neutrino-proces

Neutrino Process in Core-collapse Supernovae with Neutrino Self-interaction and MSW Effects

We investigate the nuclear abundances uniquely produced from the neutrino neutrino-process in super-nova (SN) explosion. For the first time, we have calculated the neutrino propagation including both its modification by neutrino-self-interaction (neutrino-SI) near the neutrino-sphere and the Mikheyev-Smirnov-Wolfenstein (MSW) mixing in the outer layers. We compute the neutirno-induced nucleosynthesis of 7Li, 11B, 92Nb, 98Tc, 138La, and 180Ta. Near to the neutirno-sphere, the neutrino-density is very high neutirno-SI becomes important. The interaction effect on the neutirno-process is calculated by solving the evolution equation for the neutirno-density matrix with a collision term estimated in the mean field approximation as well as the MSW (neutrino matter oscillations) in the outer layers of the SN.The light element abundances turn out to be increased by the MSW effect, but the neutirno-SI suppresses the MSW effect in the inverted hierarchy scheme. As a result, the ratio of 7Li/11B becomes lower than that of the normal hierarchy, which is consistent with more recent analysis of the meteoritic ratio