1,485 research outputs found
Upper bounds on signals due to WIMP self--annihilation: comments on the case of the synchrotron radiation from the galactic center and the WMAP haze
Two recent papers reconsider the possibility that the excess of microwave
emission from a region within of the galactic center (the {\it WMAP
haze}), measured by WMAP, can be due to the synchrotron emission originated by
neutralino self-annihilation; on the basis of this possible occurrence, also
upper bounds on the neutralino self-annihilation cross--section are suggested.
In the present note, we show that in the common case of thermal WIMPs in a
standard cosmological model, when the rescaling of the galactic WIMP density is
duly taken into account for subdominant WIMPs, the upper bound applicable
generically to {\it any} signal due to self-conjugate WIMPs is more stringent
than the ones obtained from analysis of the WMAP haze. We also argue that an
experimental upper bound, which can compete with our generic upper limit, can
rather be derived from measurements of cosmic antiproton fluxes, for some
values of the parameters of the astrophysical propagation model. Finally, we
comment on the possible impact of our generic upper bound on the interpretation
of the WMAP haze in terms of thermal neutralinos in a standard cosmological
scheme.Comment: 3 pages, comments and 1 figure adde
Implications for relic neutralinos of the theoretical uncertainties in the neutralino-nucleon cross-section
We discuss the effect induced on the neutralino-nucleon cross-section by the
present uncertainties in the values of the quark masses and of the quark scalar
densities in the nucleon. We examine the implications of this aspect on the
determination of the neutralino cosmological properties, as derived from
measurements of WIMP direct detection. We show that, within current theoretical
uncertainties, the DAMA annual modulation data are compatible with a neutralino
as a major dark matter component, to an extent which is even larger than the
one previously derived. We also comment on implications of the mentioned
uncertainties for experiments of indirect dark matter detection.Comment: 23 pages, 7 figures, 1 table, typeset with ReVTeX. Due to size
limitations, the version on the archive has low resolution figures. A full
version of the paper can be found at
http://www.to.infn.it/~fornengo/papers/dama_sets.ps.g
Decay of geodesic acoustic modes due to the combined action of phase mixing and Landau damping
Geodesic acoustic modes (GAMs) are oscillations of the electric field whose
importance in tokamak plasmas is due to their role in the regulation of
turbulence. The linear collisionless damping of GAMs is investigated here by
means of analytical theory and numerical simulations with the global
gyrokinetic particle-in-cell code ORB5. The combined effect of the phase mixing
and Landau damping is found to quickly redistribute the GAM energy in
phase-space, due to the synergy of the finite orbit width of the passing ions
and the cascade in wave number given by the phase mixing. When plasma
parameters characteristic of realistic tokamak profiles are considered, the GAM
decay time is found to be an order of magnitude lower than the decay due to the
Landau damping alone, and in some cases of the same order of magnitude of the
characteristic GAM drive time due to the nonlinear interaction with an ITG
mode. In particular, the radial mode structure evolution in time is
investigated here and reproduced quantitatively by means of a dedicated initial
value code and diagnostics.Comment: Submitted to Phys. Plasma
Relic neutralinos and the two dark matter candidate events of the CDMS II experiment
The CDMS Collaboration has presented its results for the final exposure of
the CDMS II experiment and reports that two candidate events for dark matter
would survive after application of the various discrimination and subtraction
procedures inherent in their analysis. We show that a population of relic
neutralinos, which was already proved to fit the DAMA/LIBRA data on the annual
modulation effect, could naturally explain the two candidate CDMS II events, if
these are actually due to a dark matter signal.Comment: 3 pages, 3 figure
Which fraction of the measured cosmic-ray antiprotons might be due to neutralino annihilation in the galactic halo?
We analyze the data of low-energy cosmic-ray antiproton spectrum, recently
published by the BESS Collaboration, in terms of newly calculated fluxes for
secondary antiprotons and for a possible contribution of an exotic signal due
to neutralino annihilation in the galactic halo. We single out the relevant
supersymmetric configurations and discuss their explorability with experiments
of direct search for particle dark matter and at accelerators. We discuss how
future measurements with the Alpha Magnetic Spectrometer (AMS) on the Shuttle
flight may disentangle the possible neutralino-induced contribution from the
secondary one.Comment: 25 pages, ReVTeX, 18 figures (high resolution figures available upon
request
Possible implications of the channeling effect in NaI(Tl) crystals
The channeling effect of low energy ions along the crystallographic axes and
planes of NaI(Tl) crystals is discussed in the framework of corollary
investigations on WIMP Dark Matter candidates. In fact, the modeling of this
existing effect implies a more complex evaluation of the luminosity yield for
low energy recoiling Na and I ions. In the present paper related
phenomenological arguments are developed and possible implications are
discussed at some extent.Comment: 16 pages, 10 figures, preprint ROM2F/2007/15, submitted for
publicatio
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