13,193 research outputs found
Active-Sterile Neutrino Transformation and r-Process Nucleosynthesis
The type II supernova is considered as a candidate site for the production of
heavy elements. Since the supernova produces an intense neutrino flux, neutrino
scattering processes will impact element formation. We examine active-sterile
neutrino conversion in this environment and find that it may help to produce
the requisite neutron-to-seed ratio for synthesis of the r-process elements.Comment: 5 pages including 2 figures, to appear in the Proceedings of the
Conference on the Intersections of Nuclear and Particle Physics 200
Nucleosynthesis in the Outflow from Gamma Ray Burst Accretion Disks
We examine the nucleosynthesis products that are produced in the outflow from
rapidly accreting disks. We find that the type of element synthesis varies
dramatically with the degree of neutrino trapping in the disk and therefore the
accretion rate of the disk. Disks with relatively high accretion rates such as
10 M_solar/s can produce very neutron rich nuclei that are found in the r
process. Disks with more moderate accretion rates can produce copious amounts
of Nickel as well as the light elements such as Lithium and Boron. Disks with
lower accretion rates such as 0.1 M_solar/s produce large amounts of Nickel as
well as some unusual nuclei such as Ti-49, Sc-45, Zn-64, and Mo-92. This wide
array of potential nucleosynthesis products is due to the varying influence of
electron neutrinos and antineutrinos emitted from the disk on the
neutron-to-proton ratio in the outflow. We use a parameterization for the
outflow and discuss our results in terms of entropy and outflow acceleration.Comment: 12 pages, 12 figures; submitted to Ap
Petascale computations for Large-scale Atomic and Molecular collisions
Petaflop architectures are currently being utilized efficiently to perform
large scale computations in Atomic, Molecular and Optical Collisions. We solve
the Schroedinger or Dirac equation for the appropriate collision problem using
the R-matrix or R-matrix with pseudo-states approach. We briefly outline the
parallel methodology used and implemented for the current suite of Breit-Pauli
and DARC codes. Various examples are shown of our theoretical results compared
with those obtained from Synchrotron Radiation facilities and from Satellite
observations. We also indicate future directions and implementation of the
R-matrix codes on emerging GPU architectures.Comment: 14 pages, 5 figures, 3 tables, Chapter in: Workshop on Sustained
Simulated Performance 2013, Published by Springer, 2014, edited by Michael
Resch, Yevgeniya Kovalenko, Eric Focht, Wolfgang Bez and Hiroaki Kobaysah
Neutrino Interactions in the Outflow from Gamma-Ray Burst Accretion Disks
We examine the composition of matter as it flows away from gamma ray burst
accretion disks, in order to determine what sort of nucleosynthesis may occur.
Since there is a large flux of neutrinos leaving the surface of the disk, the
electron fraction of the outflowing material will change due to charged current
neutrino interactions. We calculate the electron fraction in the wind using
detailed neutrino fluxes from every point on the disk and study a range of
trajectories and outflow conditions for several different accretion disk
models. We find that low electron fractions, conducive to making r-process
elements, only appear in outflows from disks with high accretion rates that
have a significant region both of trapped neutrinos and antineutrinos. Disks
with lower accretion rates that have only a significant region of trapped
neutrinos can have outflows with very high electron fractions, whereas the
lowest accretion rate disks with little trapping have outflow electrons
fractions of closer to one half.Comment: 11 pages, 10 figure
Understanding Supernova Neutrino Physics using Low-Energy Beta-Beams
We show that fitting linear combinations of low-energy beta-beam spectra to
supernova-neutrino energy-distributions reconstructs the response of a nuclear
target to a supernova flux in a very accurate way. This allows one to make
direct predictions about the supernova-neutrino signal in a terrestrial
neutrino detector.Comment: To appear in the proceedings of International School of Nuclear
Physics: 27th Course: "Neutrinos in Cosmology, in Astro, Particle and Nuclear
Physics". Erice, Sicily, Italy, 16-2
Reconstructing supernova-neutrino spectra using low-energy beta-beams
Only weakly interacting, neutrinos are the principal messengers reaching us
from the center of a supernova. Terrestrial neutrino telescopes, such as SNO
and SuperKamiokande, can provide precious information about the processes in
the core of a collapsing and exploding star. But the information about the
supernova that a neutrino detector can supply, is restricted by the fact that
little experimental data on the neutrino-nucleus cross sections exists and by
the uncertainties in theoretical calculations. In this letter, we propose a
novel procedure that determines the response of a target nucleus in a
supernova-neutrino detector directly, by using low-energy beta-beams. We show
that fitting 'synthetic' spectra, constructed by taking linear combinations of
beta-beam spectra, to the original supernova-neutrino spectra reproduces the
folded differential cross sections very accurately. Comparing the response in a
terrestrial detector to these synthetic responses provides a direct way to
determine the main parameters of the supernova-neutrino energy-distribution.Comment: 4 page
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