520 research outputs found
Constraints on parameters of radiatively decaying dark matter from the galaxy cluster 1E0657-56
We derived constraints on parameters of a radiatively decaying warm dark
matter particle, e.g., the mass and mixing angle for a sterile neutrino, using
Chandra X-ray spectra of a galaxy cluster 1E0657-56 (the ``bullet'' cluster).
The constraints are based on nondetection of the sterile neutrino decay
emission line. This cluster exhibits spatial separation between the hot
intergalactic gas and the dark matter, helping to disentangle their X-ray
signals. It also has a very long X-ray observation and a total mass measured
via gravitational lensing. This makes the resulting constraints on sterile
neutrino complementary to earlier results that used different cluster mass
estimates. Our limits are comparable to the best existing constraints.Comment: 6p
Sterile neutrinos in cosmology and how to find them in the lab
A number of observed phenomena in high energy physics and cosmology lack
their resolution within the Standard Model of particle physics. These puzzles
include neutrino oscillations, baryon asymmetry of the universe and existence
of dark matter. We discuss the suggestion that all these problems can be solved
by new physics which exists only below the electroweak scale. The dedicated
experiments that can confirm or rule out this possibility are discussed.Comment: Invited talk at XXIII Int. Conf. on Neutrino Physics and
Astrophysics, May 25-31, Christchurch, New Zealan
Big Bang Nucleosynthesis with Independent Neutrino Distribution Functions
We have performed new Big Bang Nucleosynthesis calculations which employ
arbitrarily-specified, time-dependent neutrino and antineutrino distribution
functions for each of up to four neutrino flavors. We self-consistently couple
these distributions to the thermodynamics, the expansion rate and scale
factor-time/temperature relationship, as well as to all relevant weak,
electromagnetic, and strong nuclear reaction processes in the early universe.
With this approach, we can treat any scenario in which neutrino or antineutrino
spectral distortion might arise. These scenarios might include, for example,
decaying particles, active-sterile neutrino oscillations, and active-active
neutrino oscillations in the presence of significant lepton numbers. Our
calculations allow lepton numbers and sterile neutrinos to be constrained with
observationally-determined primordial helium and deuterium abundances. We have
modified a standard BBN code to perform these calculations and have made it
available to the community.Comment: 9 pages, 5 figure
Dark matter sterile neutrinos in stellar collapse: alteration of energy/lepton number transport and a mechanism for supernova explosion enhancement
We investigate matter-enhanced Mikheyev-Smirnov-Wolfenstein (MSW)
active-sterile neutrino conversion in the
channel in the collapse of the iron core of a pre-supernova star. For values of
sterile neutrino rest mass and vacuum mixing angle
(specifically, ) which include those required for viable sterile neutrino
dark matter, our one-zone in-fall phase collapse calculations show a
significant reduction in core lepton fraction. This would result in a smaller
homologous core and therefore a smaller initial shock energy, disfavoring
successful shock re-heating and the prospects for an explosion. However, these
calculations also suggest that the MSW resonance energy can exhibit a minimum
located between the center and surface of the core. In turn, this suggests a
post-core-bounce mechanism to enhance neutrino transport and neutrino
luminosities at the core surface and thereby augment shock re-heating: (1)
scattering-induced or coherent MSW conversion occurs deep in
the core, at the first MSW resonance, where energies are large ( MeV); (2) the high energy stream outward at near light speed; (3)
they deposit their energy when they encounter the second MSW resonance
just below the proto-neutron star surface.Comment: 13 pages, 9 figure
Where to find a dark matter sterile neutrino?
We propose a strategy of how to look for dark matter (DM) particles
possessing a radiative decay channel and derive constraints on their parameters
from observations of X-rays from our own Galaxy and its dwarf satellites. When
applied to the sterile neutrinos in keV mass range, it allows a significant
improvement of restrictions to its parameters, as compared with previous works.Comment: 5 pp, revtex; v3: 1-sigma limits have been replaced by more
conservative 3-sigma limits, a picture illustrating the data analysis methods
has been ade
On the hadronic contribution to sterile neutrino production
Sterile neutrinos with masses in the keV range are considered to be a viable
candidate for warm dark matter. The rate of their production through
active-sterile neutrino transitions peaks, however, at temperatures of the
order of the QCD scale, which makes it difficult to estimate their relic
abundance quantitatively, even if the mass of the sterile neutrino and its
mixing angle were known. We derive here a relation, valid to all orders in the
strong coupling constant, which expresses the production rate in terms of the
spectral function associated with active neutrinos. The latter can in turn be
expressed as a certain convolution of the spectral functions related to various
mesonic current-current correlation functions, which are being actively studied
in other physics contexts. In the naive weak coupling limit, the appropriate
Boltzmann equations can be derived from our general formulae.Comment: 28 pages. v2: small clarifications added, published versio
Sterile neutrinos, dark matter, and the pulsar velocities in models with a Higgs singlet
We identify the range of parameters for which the sterile neutrinos can
simultaneously explain the cosmological dark matter and the observed velocities
of pulsars. To satisfy all cosmological bounds, the relic sterile neutrinos
must be produced sufficiently cold. This is possible in a class of models with
a gauge-singlet Higgs boson coupled to the neutrinos. Sterile dark matter can
be detected by the x-ray telescopes. The presence of the singlet in the Higgs
sector can be tested at the Large Hadron Collider.Comment: 4 pages, one figur
KeV Warm Dark Matter and Composite Neutrinos
Elementary keV sterile Dirac neutrinos can be a natural ingredient of the
composite neutrino scenario. For a certain class of composite neutrino
theories, these sterile neutrinos naturally have the appropriate mixing angles
to be resonantly produced warm dark matter (WDM). Alternatively, we show these
sterile neutrinos can be WDM produced by an entropy-diluted thermal freeze-out,
with the necessary entropy production arising not from an out-of-equilibrium
decay, but rather from the confinement of the composite neutrino sector,
provided there is sufficient supercooling.Comment: 12 pages, 2 figures, published versio
- …