7,876 research outputs found
keV sterile neutrino dark matter in gauge extensions of the standard model
It is known that a keV scale sterile neutrino is a good warm dark matter
candidate. We study how this possibility could be realized in the context of
gauge extensions of the standard model. The na\"ive expectation leads to large
thermal overproduction of sterile neutrinos in this setup. However, we find
that it is possible to use out-of-equilibrium decay of the other right-handed
neutrinos of the model to dilute the present density of the keV sterile
neutrinos and achieve the observed dark matter density. We present the
universal requirements that should be satisfied by the gauge extensions of the
standard model, containing right-handed neutrinos, to be viable models of warm
dark matter, and provide a simple example in the context of the left-right
symmetric model.Comment: RevTex, 13 pages, 5 figures; journal version (corrected typos
Leptogenesis in models with keV sterile neutrino dark matter
We analyze leptogenesis in gauge extensions of the Standard Model with keV
sterile neutrino dark matter. We find that both the observed dark matter
abundance and the correct baryon asymmetry of the Universe can simultaneously
emerge in these models. Both the dark matter abundance and the leptogenesis are
controlled by the out of equilibrium decays of the same heavy right handed
neutrino.Comment: 6 pages, 1 figur
PMT Test Facility at MPIK Heidelberg and Double Chooz Super Vertical Slice
Proceedings supplement for conference poster at Neutrino 2010, Athens,
Greece
Spatial stochastic resonance in 1D Ising systems
The 1D Ising model is analytically studied in a spatially periodic and
oscillatory external magnetic field using the transfer-matrix method. For low
enough magnetic field intensities the correlation between the external magnetic
field and the response in magnetization presents a maximum for a given
temperature. The phenomenon can be interpreted as a resonance phenomenon
induced by the stochastic heatbath. This novel "spatial stochastic resonance"
has a different origin from the classical stochastic resonance phenomenon.Comment: REVTex, 5 pages, 3 figure
Radiative Symmetry Breaking of the Minimal Left-Right Symmetric Model
Under the assumption of classical conformal invariance, we study the
Coleman-Weinberg symmetry breaking mechanism in the minimal left-right
symmetric model. This model is attractive as it provides a natural framework
for small neutrino masses and the restoration of parity as a good symmetry of
nature. We find that, in a large fraction of the parameter space, the parity
symmetry is maximally broken by quantum corrections in the Coleman-Weinberg
potential, which are a consequence of the conformal anomaly. As the left-right
symmetry breaking scale is connected to the Planck scale through the
logarithmic running of the dimensionless couplings of the scalar potential, a
large separation of the two scales can be dynamically generated. The symmetry
breaking dynamics of the model was studied using a renormalization group
analysis. Electroweak symmetry breaking is triggered by the breakdown of
left-right symmetry, and the left-right breaking scale is therefore expected in
the few TeV range. The phenomenological implications of the symmetry breaking
mechanism are discussed.Comment: 23 pages, 1 figure; version as published in journal; title changed,
changes in abstract, introduction and conclusion
En-route to the fission-fusion reaction mechanism: a status update on laser-driven heavy ion acceleration
The fission-fusion reaction mechanism was proposed in order to generate
extremely neutron-rich nuclei close to the waiting point N = 126 of the rapid
neutron capture nucleosynthesis process (r-process). The production of such
isotopes and the measurement of their nuclear properties would fundamentally
help to increase the understanding of the nucleosynthesis of the heaviest
elements in the universe. Major prerequisite for the realization of this new
reaction scheme is the development of laser-based acceleration of ultra-dense
heavy ion bunches in the mass range of A = 200 and above. In this paper, we
review the status of laser-driven heavy ion acceleration in the light of the
fission-fusion reaction mechanism. We present results from our latest
experiment on heavy ion acceleration, including a new milestone with
laser-accelerated heavy ion energies exceeding 5 MeV/u
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