30 research outputs found
Supernova Neutrino Nucleosynthesis of Light Elements with Neutrino Oscillations
Light element synthesis in supernovae through neutrino-nucleus interactions, i.e., the ν-process, is affected by neutrino oscillations in the supernova environment. There is a resonance of 13-mixing in the O/C layer, which increases the rates of charged-current ν-process reactions in the outer He-rich layer. The yields of 7Li and 11B increase by about a factor of 1.9 and 1.3, respectively, for a normal mass hierarchy and an adiabatic 13-mixing resonance, compared to those without neutrino oscillations. In the case of an inverted mass hierarchy and a non-adiabatic 13-mixing resonance, the increase in the 7Li and 11B yields is much smaller. Observations of the 7Li/11B ratio in stars showing signs of supernova enrichment could thus provide a unique test of neutrino oscillations and constrain their parameters and the mass hierarchy
Supernova Neutrino Nucleosynthesis of Light Elements with Neutrino Oscillations
Light element synthesis in supernovae through neutrino-nucleus interactions,
i.e., the nu-process, is affected by neutrino oscillations in the supernova
environment. There is a resonance of 13-mixing in the O/C layer, which
increases the rates of charged-current nu-process reactions in the outer
He-rich layer. The yields of 7Li and 11B increase by about a factor of 1.9 and
1.3, respectively, for a normal mass hierarchy and an adiabatic 13-mixing
resonance, compared to those without neutrino oscillations. In the case of an
inverted mass hierarchy and a non-adiabatic 13-mixing resonance, the increase
in the 7Li and 11B yields is much smaller. Observations of the 7Li/11B ratio in
stars showing signs of supernova enrichment could thus provide a unique test of
neutrino oscillations and constrain their parameters and the mass hierarchy.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
Neutrino-Nucleus Reaction Cross Sections for Light Element Systhesis in Supernova Explosions
The neutrino-nucleus reaction cross sections of 4He and 12C are evaluated using new shell model Hamiltoni-ans. Branching ratios of various decay channels are calculated to evaluate the yields of Li, Be, and B producedthrough the ν -process in supernova explosions. The new cross sections enhance the yields of7Li and11B pro-duced during the supernova explosion of a 16.2 M⊙star model compared to the case using the conventionalcross sections by about 10%. On the other hand, the yield of10B decreases by a factor of two. The yieldsof6Li,9Be, and the radioactive nucleus10 Be are found at a level of ∼ 10−11M⊙. The temperature of νµ,τ-and ¯νµ,τ-neutrinos inferred from the supernova contribution of11B in Galactic chemical evolution models isconstrained to the 4.3 − 6.5 MeV range. The increase in the7Li and11B yields due to neutrino oscillations isdemonstrated with the new cross section
Neutrino-Nucleus Reaction Cross Sections for Light Element Synthesis in Supernova Explosions
The neutrino-nucleus reaction cross sections of 4He and 12C are evaluated
using new shell model Hamiltonians. Branching ratios of various decay channels
are calculated to evaluate the yields of Li, Be, and B produced through the
nu-process in supernova explosions. The new cross sections enhance the yields
of 7Li and 11B produced during the supernova explosion of a 16.2 M_odot star
model compared to the case using the conventional cross sections by about 10%.
On the other hand, the yield of 10B decreases by a factor of two. The yields of
6Li, 9Be, and the radioactive nucleus 10Be are found at a level of 10^{-11}
M_odot. The temperature of nu_{mu,tau}- and bar{nu}_{mu,tau}-neutrinos inferred
from the supernova contribution of 11B in Galactic chemical evolution models is
constrained to the 4.3-6.5 MeV range. The increase in the 7Li and 11B yields
due to neutrino oscillations is demonstrated with the new cross sections.Comment: 19 pages, 30 figures, accepted for publication in Astrophysical
Journal. Typos are correcte
Neutrino Oscillation Effects on Supernova Light Element Synthesis
Neutrino oscillations affect light element synthesis through the
neutrino-process in supernova explosions. The 7Li and 11B yields produced in a
supernova explosion of a 16.2 solar-mass star model increase by factors of 1.9
and 1.3 in the case of large mixing angle solution with normal mass hierarchy
and sin^{2}2theta_{13} > 0.002 compared with those without the oscillations. In
the case of inverted mass hierarchy or nonadiabatic 13-mixing resonance, the
increment of their yields is much smaller. Neutrino oscillations raise the
reaction rates of charged-current neutrino-process reactions in the region
outside oxygen-rich layers. The number ratio of 7Li/11B could be a tracer of
normal mass hierarchy and relatively large theta_{13}, still satisfying
sin^{2}2theta_{13} < 0.1, through future precise observations in stars having
strong supernova component.Comment: 35 pages, 17 figures, accepted for publication in Astrophysical
Journa
Exact Formulas and Simple CP dependence of Neutrino Oscillation Probabilities in Matter with Constant Density
We investigate neutrino oscillations in constant matter within the context of
the standard three neutrino scenario. We derive an exact and simple formula for
the oscillation probability applicable to all channels. In the standard
parametrization, the probability for transition can
be written in the form without any
approximation using CP phase . For
transition, the linear term of is added and the probability can
be written in the form . We give the CP dependences of
the probability for other channels. We show that the probability for each
channel in matter has the same form with respect to as in vacuum. It
means that matter effects just modify the coefficients , , and .
We also give the exact expression of the coefficients for each channel.
Furthermore, we show that our results with respect to CP dependences are
reproduced from the effective mixing angles and the effective CP phase
calculated by Zaglauer and Schwarzer. Through the calculation, a new identity
is obtained by dividing the Naumov-Harrison-Scott identity by the Toshev
identity.Comment: 12 pages, RevTeX4 style, changed title, minor correction
Large-Theta(13) Perturbation Theory of Neutrino Oscillation for Long-Baseline Experiments
The Cervera et al. formula, the best known approximate formula of neutrino
oscillation probability for long-baseline experiments, can be regarded as a
second-order perturbative formula with small expansion parameter epsilon \equiv
Delta m^2_{21} / Delta m^2_{31} \simeq 0.03 under the assumption s_{13} \simeq
epsilon. If theta_{13} is large, as suggested by a candidate nu_{e} event at
T2K as well as the recent global analyses, higher order corrections of s_{13}
to the formula would be needed for better accuracy. We compute the corrections
systematically by formulating a perturbative framework by taking theta_{13} as
s_{13} \sim \sqrt{epsilon} \simeq 0.18, which guarantees its validity in a wide
range of theta_{13} below the Chooz limit. We show on general ground that the
correction terms must be of order epsilon^2. Yet, they nicely fill the mismatch
between the approximate and the exact formulas at low energies and relatively
long baselines. General theorems are derived which serve for better
understanding of delta-dependence of the oscillation probability. Some
interesting implications of the large theta_{13} hypothesis are discussed.Comment: Fig.2 added, 23 pages. Matches to the published versio