41 research outputs found

### Leptophilic Dark Matter in Direct Detection Experiments and in the Sun

Dark matter interacting predominantly with leptons instead of nuclear matter
has received a lot of interest recently. In this talk, we investigate the
signals expected from such 'leptophilic Dark Matter' in direct detection
experiments and in experiments looking for Dark Matter annihilation into
neutrinos in the Sun. In a model-independent framework, we calculate the
expected interaction rates for different scattering processes, including
elastic and inelastic scattering off atomic electron shells, as well as
loop-induced scattering off atomic nuclei. In those cases where the last effect
dominates, leptophilic Dark Matter cannot be distinguished from conventional
WIMPs. On the other hand, if inelastic scattering off the electron shell
dominates, the expected event spectrum in direct detection experiments is
different and would provide a distinct signal. However, we find that the
signals in DAMA and/or CoGeNT cannot be explained by invoking leptophilic DM
because the predicted and observed energy spectra do not match, and because of
neutrino bounds from the Sun.Comment: 7 pages, 3 figures, prepared for the Proceedings of the 8th
International Workshop on Identification of Dark Matter (IDM 2010), July
26-30, 2010, University of Montpellier II, Montpellier, Franc

### Enhancing Dark Matter Annihilation into Neutrinos

We perform a detailed and quasi model-independent analysis of direct
annihilation of Dark Matter into neutrinos. Considering different cases for
scalar and fermionic Dark Matter, we identify several settings in which this
annihilation is enhanced, contrary to some statements in the literature. They
key point is that several restrictions of, e.g., a supersymmetric framework do
not hold in general. The mass generation mechanism of the neutrinos plays an
important role, too. We illustrate our considerations by two examples that are
not (as usually) suppressed by the smallness of the neutrino mass, for which we
also present a numerical analysis. Our results can be easily used as guidelines
for model building.Comment: 33 pages, 2 figure

### On the Consistency of Perturbativity and Gauge Coupling Unification

We investigate constraints that the requirements of perturbativity and gauge
coupling unification impose on extensions of the Standard Model and of the
MSSM. In particular, we discuss the renormalization group running in several
SUSY left-right symmetric and Pati-Salam models and show how the various scales
appearing in these models have to be chosen in order to achieve unification. We
find that unification in the considered models occurs typically at scales below
M^{min}_{B violation} = 10^16 GeV, implying potential conflicts with the
non-observation of proton decay. We emphasize that extending the particle
content of a model in order to push the GUT scale higher or to achieve
unification in the first place will very often lead to non-perturbative
evolution. We generalize this observation to arbitrary extensions of the
Standard Model and of the MSSM and show that the requirement of perturbativity
up to M^{min}_{B violation}, if considered a valid guideline for model
building, severely limits the particle content of any such model, especially in
the supersymmetric case. However, we also discuss several mechanisms to
circumvent perturbativity and proton decay issues, for example in certain
classes of extra dimensional models.Comment: LaTeX, 20 pages, 8 figures, 1 tabl

### Indirect detection of Dark Matter with neutrinos

In this doctoral thesis, we discuss indirect Dark Matter detection with neutrinos. We perform a detailed calculation of the neutrino spectra coming from Dark Matter annihilations inside the Sun and the Earth, taking into account all the possible processes that could occur during propagation: oscillation and interaction with matter. We examine in a systematic way the possibilities of Dark Matter annihilation directly into neutrinos, considering the case of scalar and fermionic Dark Matter. We explicitly calculate the annihilation cross section for different typologies of diagrams. We identify the most favourable scenarios, for which the behaviour of the cross section is given. We then describe the phenomenology of the leptophilic Dark Matter and show how experimental bounds on the neutrino flux coming from annihilations inside the Sun disfavour this model as explanation of the DAMA results. Finally, a carefull analysis of the neutrino flux expected from neutralino annihilations inside the Sun and the Earth is presented. We consider uncertainties coming from both particle physics and astrophysics and we divide the fluxes in through-going and stopping muons

### On Probing theta_{23} in Neutrino Telescopes

Among all neutrino mixing parameters, the atmospheric neutrino mixing angle
theta_{23} introduces the strongest variation on the flux ratios of ultra high
energy neutrinos. We investigate the potential of these flux ratio measurements
at neutrino telescopes to constrain theta_{23}. We consider astrophysical
neutrinos originating from pion, muon-damped and neutron sources and make a
comparative study of their sensitivity reach to theta_{23}. It is found that
neutron sources are most favorable for testing deviations from maximal
theta_{23}. Using a chi^2 analysis, we show in particular the power of
combining (i) different flux ratios from the same type of source, and also (ii)
combining flux ratios from different astrophysical sources. We include in our
analysis ``impure'' sources, i.e., deviations from the usually assumed initial
(1 : 2 : 0), (0 : 1 : 0) or (1 : 0 : 0) flux compositions.Comment: 17 pages, 5 figures. Added discussion on experimental errors. To
appear in PR

### Neutrino mass limits: robust information from the power spectrum of galaxy surveys

We present cosmological upper limits on the sum of active neutrino masses using large-scale power spectrum data from the WiggleZ Dark Energy Survey and from the Sloan Digital Sky Survey - Data Release 7 (SDSS-DR7) sample of Luminous Red Galaxies (LRG). Combining measurements on the Cosmic Microwave Background temperature and polarisation anisotropies by the Planck satellite together with WiggleZ power spectrum results in a neutrino mass bound of 0.37 eV at 95% C.L., while replacing WiggleZ by the SDSS-DR7 LRG power spectrum, the 95% C.L. bound on the sum of neutrino masses is 0.38 eV. Adding Baryon Acoustic Oscillation (BAO) distance scale measurements, the neutrino mass upper limits greatly improve, since BAO data break degeneracies in parameter space. Within a Î›CDM model, we find an upper limit of 0.13 eV (0.14 eV) at 95% C.L., when using SDSS-DR7 LRG (WiggleZ) together with BAO and Planck. The addition of BAO data makes the neutrino mass upper limit robust, showing only a weak dependence on the power spectrum used. We also quantify the dependence of neutrino mass limit reported here on the CMB lensing information. The tighter upper limit (0.13 eV) obtained with SDSS-DR7 LRG is very close to that recently obtained using Lyman-alpha clustering data, yet uses a completely different probe and redshift range, further supporting the robustness of the constraint. This constraint puts under some pressure the inverted mass hierarchy and favours the normal hierarchy

### Soft L_e-L_mu-L_tau flavour symmetry breaking and sterile neutrino keV Dark Matter

We discuss how a $L_e-L_\mu-L_\tau$ flavour symmetry that is softly broken
leads to keV sterile neutrinos, which are a prime candidate for Warm Dark
Matter. This is to our knowledge the first model where flavour symmetries are
applied simultaneously to active and sterile neutrinos explaining at the same
time active neutrino properties and this peculiar Dark Matter scenario. The
essential point is that different scales of the symmetry breaking and the
symmetry preserving entries in the mass matrix lead to one right-handed
neutrino which is nearly massless compared to the other two. Furthermore, we
naturally predict vanishing $\theta_{13}$ and maximal $\theta_{23}$, while the
correct value of $\theta_{12}$ must come from the mixing of the charged
leptons. We can furthermore predict an exact mass spectrum for the light
neutrinos, which will be testable in the very near future.Comment: 14 page

### An accurate analytic description of neutrino oscillations in matter

A simple closed-form analytic expression for the probability of two-flavour
neutrino oscillations in a matter with an arbitrary density profile is derived.
Our formula is based on a perturbative expansion and allows an easy calculation
of higher order corrections. The expansion parameter is small when the density
changes relatively slowly along the neutrino path and/or neutrino energy is not
very close to the Mikheyev-Smirnov-Wolfenstein (MSW) resonance energy. Our
approximation is not equivalent to the adiabatic approximation and actually
goes beyond it. We demonstrate the validity of our results using a few model
density profiles, including the PREM density profile of the Earth. It is shown
that by combining the results obtained from the expansions valid below and
above the MSW resonance one can obtain a very good description of neutrino
oscillations in matter in the entire energy range, including the resonance
region.Comment: 16 pages,6 figure