14,655 research outputs found
Constraining Galactic dark matter with gamma-ray pixel counts statistics
Gamma-ray searches for new physics such as dark matter are often driven by
investigating the composition of the extragalactic gamma-ray background (EGB).
Classic approaches to EGB decomposition manifest in resolving individual point
sources and dissecting the intensity spectrum of the remaining unresolved
component. Furthermore, statistical methods have recently been proven to
outperform the sensitivity of classic source detection algorithms in finding
point-source populations in the unresolved flux regime. In this article, we
employ the 1-point photon count statistics of eight years of Fermi-LAT data to
resolve the population of extragalactic point sources and to decompose the
diffuse isotropic background contribution for Galactic latitudes |b|>30 deg. We
use three adjacent energy bins between 1 and 10 GeV. For the first time, we
extend the analysis to incorporate a potential contribution from annihilating
dark matter smoothly distributed in the Galaxy. We investigate the sensitivity
reach of 1-point statistics for constraining the thermally-averaged
self-annihilation cross section of dark matter, using different
template models for the Galactic foreground emission. Given the official
Fermi-LAT interstellar emission model, we set upper bounds on the DM
self-annihilation cross section that are comparable with the
constraints obtained by other indirect detection methods, in particular by the
stacking analysis of several dwarf spheroidal galaxies.Comment: 11 pages, 7 figures, 1 table; v2: major changes improving the
selection of the RO
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
Search for the SM Higgs boson decaying to b quarks with CMS experiment
A search for the Standard Model (SM) Higgs boson decaying to
bottom quarks pairs is presented. Two production channels have been analyzed: vector-boson fusion and associated production with a vector boson decaying to leptons. The search is performed on data collected with the CMS detector at LHC during 2011 and 2012, at center-of-mass energies of 7 and 8TeV, corresponding to integrated luminosities of about 5.0 fb−1 and 19.0 fb−1, respectively. A 95% confidence
level upper limit of 1.79 (0.89) times SM Higgs boson cross section has been observed (expected) at a Higgs boson mass of 125GeV. An excess of events is observed above the expected background with a local significance of 2.2 standard deviations, which is consistent with the expectation from the production of the SM Higgs boson. The signal strength corresponding to this excess, relative to that of the SM Higgs boson, is 0.97 ± 0.48
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
Analytical results for long time behavior in anomalous diffusion
We investigate through a Generalized Langevin formalism the phenomenon of
anomalous diffusion for asymptotic times, and we generalized the concept of the
diffusion exponent. A method is proposed to obtain the diffusion coefficient
analytically through the introduction of a time scaling factor . We
obtain as well an exact expression for for all kinds of diffusion.
Moreover, we show that is a universal parameter determined by the
diffusion exponent. The results are then compared with numerical calculations
and very good agreement is observed. The method is general and may be applied
to many types of stochastic problem
Constraints on WIMP Dark Matter from the High Energy PAMELA data
A new calculation of the ratio in cosmic rays is compared to the
recent PAMELA data. The good match up to 100 GeV allows to set constraints on
exotic contributions from thermal WIMP dark matter candidates. We derive
stringent limits on possible enhancements of the WIMP \pbar flux: a =100 GeV (1 TeV) signal cannot be increased by more than a factor 6 (40)
without overrunning PAMELA data. Annihilation through the channel is
also inspected and cross-checked with data. This scenario is
strongly disfavored as it fails to simultaneously reproduce positron and
antiproton measurements.Comment: 5 pages, 5 figures, the bibliography has been updated, minor
modifications have been made in the tex
- …