Nicole F. Bell

Decay of high-energy astrophysical neutrinos

Existing limits on the nonradiative decay of one neutrino to another plus a massless particle (e.g., a singlet Majoron) are very weak. The best limits on the lifetime to mass ratio come from solar neutrino observations and are tau/m greater, similar 10(-4) s/eV for the relevant mass eigenstate(s). For lifetimes even several orders of magnitude longer, high-energy neutrinos from distant astrophysical sources would decay. This would strongly alter the flavor ratios from the phi(nu(e)):phi(nu(mu)):phi(nu(tau))=1:1:1 expected from oscillations alone and should be readily visible in the near future in detectors such as IceCube.

Do solar neutrinos decay

Despite the fact that the solar neutrino flux is now well understood in the context of matter-affected neutrino mixing, we find that it is not yet possible to set a strong and model-independent bound on solar neutrino decays. If neutrinos decay into truly invisible particles, the Earth-Sun baseline defines a lifetime limit of

Searching for Dark Matter at the LHC with a Mono-Z

\ensuremath{\tau}/m\ensuremath{\gtrsim}{10}^{\ensuremath{-}4} \mathrm{s}/\mathrm{e}\mathrm{V}.

Pseudo-Dirac Neutrinos: A Challenge for Neutrino Telescopes

However, there are many possibilities which must be excluded before such a bound can be established. There is an obvious degeneracy between the neutrino lifetime and the mixing parameters. More generally, one must also allow the possibility of active daughter neutrinos and/or antineutrinos, which may partially conceal the characteristic features of decay. Many of the most exotic possibilities that presently complicate the extraction of a decay bound will be removed if the KamLAND reactor antineutrino experiment confirms the large-mixing angle solution to the solar neutrino problem and measures the mixing parameters precisely. Better experimental and theoretical constraints on the

Cosmological signatures of interacting neutrinos

{}^{8}\mathrm{B}

Upper bound on the dark matter total annihilation cross section.

neutrino flux will also play a key role, as will tighter bounds on absolute neutrino masses. Though the lifetime limit set by the solar flux is weak, it is still the strongest direct limit on nonradiative neutrino decay. Even so, there is no guarantee (by about eight orders of magnitude) that neutrinos from astrophysical sources such as a Galactic supernova or distant active galactic nuclei will not decay.

Sensitivity to θ 13 and δ in the decaying astrophysical neutrino scenario

We investigate a mono-Z process as a potential dark matter search strategy at the LHC. In this channel a single Z boson recoils against missing transverse momentum, attributed to dark matter particles,

Electroweak bremsstrahlung in dark matter annihilation

\chi

Dark matter annihilation signatures from electroweak bremsstrahlung

, which escape the detector. This search strategy is related, and complementary to, monojet and monophoton searches. For illustrative purposes we consider the process

Radio and gamma-ray constraints on dark matter annihilation in the Galactic center

q\bar{q} -> \chi\chi Z