9,712 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
Photoionization cross section calculations for the halogen-like ions Kr and Xe
Photoionization cross sections calculations on the halogen-like ions; Kr
and Xe have been performed for a photon energy range from each ion
threshold to 15 eV, using large-scale close-coupling calculations within the
Dirac-Coulomb R-matrix approximation. The results from our theoretical work are
compared with recent measurements made at the ASTRID merged-beam set-up at the
University of Aarhus in Denmark and from the Fourier transform ion cyclotron
resonance (FT-ICR) trap method at the SOLEIL synchrotron radiation facility in
Saint-Aubin, France and the Advanced Light Soure (ALS). For each of these
complex ions our theoretical cross section results over the photon energy range
investigated are seen to be in excellent agreement with experiment. Resonance
energy positions and quantum defects of the prominent Rydberg resonances series
identified in the spectra are compared with experiment for these complex
halogen like-ions.Comment: Accepted for publicatio
Oscillation Effects and Time Variation of the Supernova Neutrino Signal
The neutrinos detected from the next Galactic core-collapse supernova will
contain valuable information on the internal dynamics of the explosion. One
mechanism leading to a temporal evolution of the neutrino signal is the
variation of the induced neutrino flavor mixing driven by changes in the
density profile. With one and two dimensional hydrodynamical simulations we
identify the behavior and properties of prominent features of the explosion.
Using these results we demonstrate the time variation of the neutrino crossing
probabilities due to changes in the MSW neutrino transformations as the star
explodes by using the S-matrix - Monte Carlo - approach to neutrino
propagation. After adopting spectra for the neutrinos emitted from the
proto-neutron star we calculate for a Galactic supernova the evolution of the
positron spectra within a water Cerenkov detector and the ratio of charged
current to neutral current event rates for a heavy water - SNO like - detector
and find that these detector signals are feasible probes of a number of
explosion features
RISK OF HEAD INJURY FROM FALLS ON TAEKWONDO MATS
The aim of this project was to determine the risk of head injury from falls without protective headgear onto 5 different taekwondo mats. In addition, the combined shock absorption of the headgear and mats adopted by the Australian taekwondo team was assessed. An artificial headform with accelerometers was dropped from a height of 1.5 m onto the mats. The acceleration data were used to calculate the Head Injury Criterion (HIC). Results revealed that only one mat had sufficient shock absorption to generate a HIC value below the threshold for head injury for drops with the unprotected headfotm. The combination of the protective headgear and mats adopted by the Australian taekwondo team produced HIC values below the injury threshold. It is recommended that taekwondo athletes wear protective headgear at all times when training
Induced antiferromagnetism and large magnetoresistances in RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates
RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates have been studied by neutron
diffraction, magnetotransport and magnetisation measurements and the electronic
phase diagram is reported. Separate Ru and Cu spin ordering transitions are
observed, with spontaneous Cu antiferromagnetic order for low hole doping
levels p, and a distinct, induced-antiferromagnetic Cu spin phase in the 0.02 <
p < 0.06 pseudogap region. This ordering gives rise to large negative
magnetoresistances which vary systematically with p in the
RuSr2Nd1.8-xY0.2CexCu2O10-d series. A collapse of the magnetoresistance (MR)
and magnetisation in the pre-superconducting region may signify the onset of
superconducting fluctuations.Comment: 22 pages, 11 figure
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