8 research outputs found
A Tight Connection Between Direct and Indirect Detection of Dark Matter through Higgs Portal Couplings to a Hidden Sector
We present a hidden Abelian extension of the Standard Model including a
complex scalar as a dark matter candidate and a light scalar acting as a long
range force carrier between dark matter particles. The Sommerfeld enhanced
annihilation cross-section of the dark matter explains the observed cosmic ray
excesses. The light scalar field also gives rise to potentially large
cross-sections of dark matter on nucleon, therefore providing an interesting
way to probe this model simultaneously at direct and indirect dark matter
search experiments. We constrain the parameter-space of the model by taking
into account CDMS-II exclusion limit as well as PAMELA and FermiLAT data.Comment: 15 pages, 7 figures. Added discussions on tuning and inverse Compton
scattering constraints. References added and updated. Matches the published
versio
Flavour Matters in Leptogenesis
We give analytic approximations to the baryon asymmetry produced by thermal
leptogenesis with hierarchical right-handed neutrinos. Our calculation includes
flavour-dependent washout processes and CP violation in scattering, and
neglects gauge interactions and finite temperature corrections. Our approximate
formulae depend upon the three CP asymmetries in the individual lepton flavours
as well as on three flavour-dependent efficiency factors. We show that the
commonly used expressions for the lepton asymmetry, which depend on the total
CP asymmetry and one single efficiency factor, may fail to reproduce the
correct lepton asymmetry in a number of cases. We illustrate the importance of
using the flavour-dependent formulae in the context of a two right-handed
neutrino model.Comment: Additional typos corrected (in particular, the plots and captions now
agree
Constraining Sommerfeld Enhanced Annihilation Cross-sections of Dark Matter via Direct Searches
In a large class of models we show that the light scalar field responsible
for the Sommerfeld enhancement in the annihilation of dark matter leads to
observable direct detection rates, due to its mixing with the standard model
Higgs. As a result the large annihilation cross-section of dark matter at
present epoch, required to explain the observed cosmic ray anomalies, can be
strongly constrained by direct searches. In particular Sommerfeld boost factors
of order of a few hundred are already out of the CDMS-II upper bound at 90%
confidence level for reasonable values of the model parameters.Comment: 6 pages, 5 figures. v2: discussion on BBN constraints added and BBN
bounds implementend in figure 3, updated references. Version to appear on
Phys.Lett.
Successful Leptogenesis in SO(10) Unification with a Left-Right Symmetric Seesaw Mechanism
We study thermal leptogenesis in a broad class of supersymmetric SO(10)
models with a left-right symmetric seesaw mechanism, taking into account
flavour effects and the contribution of the next-to-lightest right-handed
neutrino supermultiplet. Assuming M_D = M_u and a normal hierarchy of light
neutrino masses, we show that four out of the eight right-handed neutrino mass
spectra reconstructed from low-energy neutrino data can lead to successful
leptogenesis with a reheating temperature in the (10^9 - 10^10) GeV range. In
the remaining four solutions, leptogenesis is dominated by N_2 decays, as in
the type I seesaw case. We find that some of these spectra can generate the
observed baryon asymmetry for reheating temperatures above 10^10 GeV, in
contrast to the type I case. Together with flavour effects, an accurate
description of charged fermion masses turns out to be a crucial ingredient in
the analysis.Comment: 32 pages, 23 figures. v2: 2 comments [below Eq. (53) and at the end
of the conclusions] and 1 reference added, typos corrected. Version to be
published in Nucl. Phys.
Récents développements en leptogénèse (le rôle des saveurs dans diverses réalisations du modèle du seesaw)
ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF