25,109 research outputs found
CP, T and CPT violation in future long baseline experiments
I give a short overview about the possibilities and problems related to the
measurement of CP violation in long baseline experiments. Special attention is
paid to the issue of degeneracies and a method for their resolution is
quantitatively discussed. The CP violation reach for different experiments is
compared in dependence of and \dm{21}. Furthermore a
short comment about the possible effects of matter induced T violation is made.
Finally the limits on CPT violation obtainable at a neutrino factory are shown.Comment: Talk presented at NUFACT02, London, 1-6 July, 2002. 3 pages, 2
figure
On the determination of anti-neutrino spectra from nuclear reactors
In this paper we study the effect of, well-known, higher order corrections to
the allowed beta decay spectrum on the determination of anti-neutrino spectra
resulting from the decays of fission fragments. In particular, we try to
estimate the associated theory errors and find that induced currents like weak
magnetism may ultimately limit our ability to improve the current accuracy and
under certain circumstance could even largely increase the theoretical errors.
We also perform a critical evaluation of the errors associated with our method
to extract the anti-neutrino spectrum using synthetic beta spectra. It turns
out, that a fit using only virtual beta branches with a judicious choice of the
effective nuclear charge provides results with a minimal bias. We apply this
method to actual data for U235, Pu239 and Pu241 and confirm, within errors,
recent results, which indicate a net 3% upward shift in energy averaged
anti-neutrino fluxes. However, we also find significant shape differences which
can in principle be tested by high statistics anti-neutrino data samples.Comment: 20 pages, 5 figures, 9 tables, added references, version accepted for
publication in Phys. Rev. C. Corrected errors in tab. 1 and eqs. 18 and 19.
Results and conclusion unchange
Top transport in electroweak baryogenesis
In non-supersymmetric models of electroweak baryogenesis the top quark plays
a crucial role. Its CP-violating source term can be calculated in the WKB
approximation. We point out how to resolve certain discrepancies between
computations starting from the Dirac equation and the Schwinger--Keldysh
formalism. We also improve on the transport equations, keeping the
W-scatterings at finite rate. We apply these results to a model with one Higgs
doublet, augmented by dimension-6 operators, where our refinements lead to an
increase in the baryon asymmetry by a factor of up to about 5.Comment: 17 pages, 3 figures, references adde
Gravitational waves from the sound of a first order phase transition
We report on the first three-dimensional numerical simulations of first-order phase transitions in the early Universe to include the cosmic fluid as well as the scalar field order parameter. We calculate the gravitational wave (GW) spectrum resulting from the nucleation, expansion, and collision of bubbles of the low-temperature phase, for phase transition strengths and bubble wall velocities covering many cases of interest. We find that the compression waves in the fluid continue to be a source of GWs long after the bubbles have merged, a new effect not taken properly into account in previous modeling of the GW source. For a wide range of models, the main source of the GWs produced by a phase transition is, therefore, the sound the bubbles make
SWEEPFINDER2: Increased sensitivity, robustness, and flexibility
SweepFinder is a popular program that implements a powerful likelihood-based
method for detecting recent positive selection, or selective sweeps. Here, we
present SweepFinder2, an extension of SweepFinder with increased sensitivity
and robustness to the confounding effects of mutation rate variation and
background selection, as well as increased flexibility that enables the user to
examine genomic regions in greater detail and to specify a fixed distance
between test sites. Moreover, SweepFinder2 enables the use of invariant sites
for sweep detection, increasing both its power and precision relative to
SweepFinder
Hyperons and massive neutron stars: vector repulsion and SU(3) symmetry
With the discovery of massive neutron stars such as PSR J1614-2230, the
question has arisen whether exotic matter such as hyperons can exist in the
neutron star core. We examine the conditions under which hyperons can exist in
massive neutron stars. We consistently investigate the vector meson-hyperon
coupling, going from SU(6) quark model to a broader SU(3) symmetry. We propose
that the maximum neutron star mass decreases linearly with the strangeness
content f_s of the neutron star core as M_max(f_s) = M_max(0) - 0.6 M_solar
(f_s/0.1), which seems to be independent of the underlying nuclear equation of
state and the vector baryon-meson coupling scheme. Thus, pulsar mass
measurements can be used to constrain the hyperon fraction in neutron stars.Comment: 13 pages, 10 figure
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