21,180 research outputs found
Weak reactions on 12C within the Continuum Random Phase Approximation with partial occupancies
We extend our previous studies of the neutrino-induced reactions on 12C and
muon capture to include partial occupation of nuclear subshells in the
framework of the continuum random phase approximation. We find, in contrast to
the work by Auerbach et al., that a partial occupation of the p1/2 subshell
reduces the inclusive cross sections only slightly. The extended model
describes the muon capture rate and the 12C(nu_e,e-)12N cross section very
well. The recently updated flux and the improved model bring the calculated
12C(nu_mu,mu^-)12N cross section (~ 17.5 10^{-40} cm^2) and the data (12.4 +/-
0.3(stat.) +/- 1.8(syst.) 10^{-40} cm^2) closer together, but does not remove
the discrepancy fully.Comment: 12 pages, 2 figure
Estimates of weak and electromagnetic nuclear decay signatures for neutrino reactions in Super-Kamiokande
We estimate possible delayed β decay signatures of the neutrino induced reactions on 16O in a two-step model: the primary neutrino (ν,l) process, where l is the lepton in the final state, is described within the random phase approximation, while the subsequent decay of the excited nuclear state in the final channel is treated within the statistical model. We calculate partial reaction cross sections leading to β unstable nuclei. We consider neutrino energies up to 500 MeV, relevant for atmospheric neutrino detection in Super-Kamiokande, and supernova neutrino spectra
Quasielastic neutrino scattering from oxygen and the atmospheric neutrino problem
We examine several phenomena beyond the scope of Fermi-gas models that affect
the quasielastic scattering (from oxygen) of neutrinos in the 0.1 -- 3.0 GeV
range. These include Coulomb interactions of outgoing protons and leptons, a
realistic finite-volume mean field, and the residual nucleon-nucleon
interaction. None of these effects are accurately represented in the Monte
Carlo simulations used to predict event rates due to and neutrinos
from cosmic-ray collisions in the atmosphere. We nevertheless conclude that the
neglected physics cannot account for the anomalous to ratio observed
at Kamiokande and IMB, and is unlikely to change absolute event rates by more
than 10--15\%. We briefly mention other phenomena, still to be investigated in
detail, that may produce larger changes.Comment: In Revtex version 2. 14 pages, 3 figures (available on request from
J. Engel, tel. 302-831-4354, [email protected]
Uncertainties in nuclear transition matrix elements for neutrinoless decay II: the heavy Majorana neutrino mass mechanism
Employing four different parametrization of the pairing plus multipolar type
of effective two-body interaction and three different parametrizations of
Jastrow-type of short range correlations, the uncertainties in the nuclear
transition matrix elements due to the exchange of heavy
Majorana neutrino for the transition of neutrinoless
double beta decay of Zr, Zr, Mo, Mo, Ru,
Pd, Te and Nd isotopes in the PHFB model are
estimated to be around 25%. Excluding the nuclear transition matrix elements
calculated with Miller-Spenser parametrization of Jastrow short range
correlations, the uncertainties are found to be 10%-15% smaller
Neutrino–nucleus reactions and nuclear structure
The methods used in the evaluation of the neutrino–nucleus cross section are reviewed. Results are shown for a variety of targets of practical importance. Many of the described reactions are accessible in future experiments with neutrino sources from the pion and muon decays at rest, which might be available at the neutron spallation facilities. Detailed comparison between the experimental and theoretical results would establish benchmarks needed for verification and/or parameter adjustment of the nuclear models. Having a reliable tool for such calculation is of great importance in a variety of applications, e.g. the neutrino oscillation studies, detection of supernova neutrinos, description of the neutrino transport in supernovae and description of the r-process nucleosynthesis
Neutrino-induced nucleosynthesis and the site of the r process
If the r process occurs deep within a type II supernova, probably the most popular of the proposed sites, abundances of r-process elements may be altered by the intense neutrino flux. We point out that the effects would be especially pronounced for eight isotopes that can be efficiently synthesized by the neutrino reactions following r-process freeze-out. We show that the observed abundances of these isotopes are entirely consistent with neutrino-induced nucleosynthesis, strongly arguing for a supernova r-process site. The deduced neutrino fluences place stringent constraints on the freeze-out radius and dynamic time scale of the r process
Reactor antineutrino spectra and their application to antineutrino-induced reactions. II
The antineutrino and electron spectra associated with various nuclear fuels are calculated. While there are substantial differences between the spectra of different uranium and plutonium isotopes, the dependence on the energy and flux of the fission-inducing neutrons is very weak. The resulting spectra can be used for the calculation of the antineutrino and electron spectra of an arbitrary nuclear reactor at various stages of its refueling cycle. The sources of uncertainties in the spectrum are identified and analyzed in detail. The exposure time dependence of the spectrum is also discussed. The averaged cross sections of the inverse neutron β decay, weak charged and neutral-current-induced deuteron disintegration, and the antineutrino-electron scattering are then evaluated using the resulting ν̅_e spectra.
[RADIOACTIVITY, FISSION 235U, 238U, (^239)Pu, (^240)Pu, (^241)Pu, antineutrino and electron spectra calculated. σ for ν̅ induced reactions analyzed.
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