7,759 research outputs found
Three Flavor Neutrino Oscillations in Matter: Flavor Diagonal Potentials, the Adiabatic Basis and the CP phase
We discuss the three neutrino flavor evolution problem with general,
flavor-diagonal, matter potentials and a fully parameterized mixing matrix that
includes CP violation, and derive expressions for the eigenvalues, mixing
angles and phases. We demonstrate that, in the limit that the mu and tau
potentials are equal, the eigenvalues and matter mixing angles theta_12 and
theta_13 are independent of the CP phase, although theta_23 does have CP
dependence. Since we are interested in developing a framework that can be used
for S matrix calculations of neutrino flavor transformation, it is useful to
work in a basis that contains only off-diagonal entries in the Hamiltonian. We
derive the "non-adiabaticity" parameters that appear in the Hamiltonian in this
basis. We then introduce the neutrino S matrix, derive its evolution equation
and the integral solution. We find that this new Hamiltonian, and therefore the
S matrix, in the limit that the mu and tau neutrino potentials are the same, is
independent of both theta_23 and the CP violating phase. In this limit, any CP
violation in the flavor basis can only be introduced via the rotation matrices,
and so effects which derive from the CP phase are then straightforward to
determine. We show explicitly that the electron neutrino and electron
antineutrino survival probability is independent of the CP phase in this limit.
Conversely, if the CP phase is nonzero and mu and tau matter potentials are not
equal, then the electron neutrino survival probability cannot be independent of
the CP phase
Manipulating a Neutrino Spectrum to Maximize the Physics Potential from a Low Energy Beta Beam
Proposed low energy beta beam facilities would be capable of producing
intense beams of neutrinos (anti-neutrinos) with well defined spectra. We
present analytic expressions and numerical results which accurately show how
the total neutrino flux reaching the detector depends on the geometry of the
source and the detector. Several authors have proposed measurements which
require using different flux shapes. We show that detectors of different sizes
and shapes will receive neutrino fluxes with different spectral shapes, and
that the spectral shape will also be different in different regions of the same
detector. Our findings also show that for certain measurements systematic
uncertainties and run time can be reduced.Comment: 18 pages, 10 figure
On the Contribution of Gamma Ray Bursts to the Galactic Inventory of Some Intermediate Mass Nuclei
Light curves from a growing number of Gamma Ray Bursts (GRBs) indicate that
GRBs copiously produce radioactive Ni moving outward at fractions of the speed
of light. We calculate nuclear abundances of elements accompanying the
outflowing Ni under the assumption that this Ni originates from a wind blown
off of a viscous accretion disk. We also show that GRB's likely contribute
appreciably to the galactic inventory of 42Ca, 45Sc, 46Ti, 49Ti, 63Cu, and may
be a principal site for the production of 64Zn.Comment: 11 pages, 1 figur
Childhood mental health: an ecological analysis of the effects of neighborhood characteristics
Research on childhood mental illness traditionally examines risk factors most proximal to the child. However, current trends reflect growing interest in how broader contextual factors contribute to psychopathology risk. In this study, we examined neighborhoodâlevel indicators as potential sources of chronic strain in a sample of 156 motherâchild dyads; children were 8 to 12 years old. For most neighborhood indicators, data were collected at the level of census tracts using publicly available data sets. We hypothesized that these indicators would be both associated with greater overall mental health symptoms and specifically predictive of childhood symptoms of depression. We also examined potential mediators (maternal functioning and family cohesion) and moderators (maternal depression). Neighborhood indicators correlated with parentsâ ratings of children's overall mental health problems, but did not correlate with children's selfâreport of depression symptoms. Maternal functioning mediated neighborhood effects on children's overall mental health problems. Implications and directions for future research are presented.The current work was supported by the following grants from the National Institutes of Health, National Institute of Mental Health MH066077, MH082861, PI: Martha C. Tompson, Ph.D. and MH082861S1, PI: Gail N. Kemp, M.A., M.P.H. (MH066077 - National Institutes of Health, National Institute of Mental Health; MH082861 - National Institutes of Health, National Institute of Mental Health; MH082861S1 - National Institutes of Health, National Institute of Mental Health)Published versio
Neutrino Capture and r-Process Nucleosynthesis
We explore neutrino capture during r-process nucleosynthesis in
neutrino-driven ejecta from nascent neutron stars. We focus on the interplay
between charged-current weak interactions and element synthesis, and we
delineate the important role of equilibrium nuclear dynamics. During the period
of coexistence of free nucleons and light and/or heavy nuclei, electron
neutrino capture inhibits the r-process. At all stages, capture on free
neutrons has a larger impact than capture on nuclei. However, neutrino capture
on heavey nuclei by itself, if it is very strong, is also detrimental to the
r-process until large nuclear equilibrium clusters break down and the classical
neutron-capture phase of the r-process begins. The sensitivity of the r-process
to neutrino irradiation means that neutrino-capture effects can strongly
constrain the r-process site, neutrino physics, or both. These results apply
also to r-process scenarios other than neutrino-heated winds.Comment: 20 pages, 17 figures, Submitted to Physical Review
Neutrino-nucleus coherent scattering as a probe of neutron density distributions
Neutrino-nucleus coherent elastic scattering provides a theoretically
appealing way to measure the neutron part of nuclear form factors. Using an
expansion of form factors into moments, we show that neutrinos from stopped
pions can probe not only the second moment of the form factor (the neutron
radius) but also the fourth moment. Using simple Monte Carlo techniques for
argon, germanium, and xenon detectors of 3.5 tonnes, 1.5 tonnes, and 300 kg,
respectively, we show that the neutron radii can be found with an uncertainty
of a few percent when near a neutrino flux of
neutrinos/cm/s. If the normalization of the neutrino flux is known
independently, one can determine the moments accurately enough to discriminate
among the predictions of various nuclear energy functionals.Comment: 10 pages, 5 figure
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