* Astronomy

Title: Are Light Sterile Neutrinos Consistent with Supernova Explosions?
Authors: Meng-Ru Wu, Tobias Fischer, Gabriel Martínez-Pinedo, Yong-Zhong Qian

We point out that for sterile neutrinos of the eV mass scale with mixing parameters suggested by the reactor neutrino anomaly, substantial flavour transformation occurs in both \nu_e-\nu_s and \bar \nu_e-\bar \nu_s channels near a supernova core where the electron-to-baryon ratio is \approx 1/3. We show that the rate of heating by neutrino reactions in the shocked material is significantly reduced for ~ 100 ms after the launch of the shock in spherically symmetric models of 8.8 and 11.2 solar masses supernovae. While the exact consequences must be evaluated by incorporating \nu_e-\nu_s and \bar \nu_e-\bar \nu_s conversion self-consistently in the models, our results suggest that such flavour transformation would have important effects on the supernova explosion mechanisms and possibly also on nucleosynthesis in the neutrino-heated ejecta. We explore the sensitivity of our results to the mixing parameters and urge that self-consistent supernova models be developed to constrain the allowed parameter space.

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Title: Testing for Large Extra Dimensions with Neutrino Oscillations
Authors: P. A. N. Machado, H. Nunokawa, R. Zukanovich Funchal

We consider a model where sterile neutrinos can propagate in a large compactified extra dimension giving rise to Kaluza-Klein (KK) modes and the Standard Model left-handed neutrinos are confined to a 4-dimensional spacetime brane. The KK modes mix with the standard neutrinos modifying their oscillation pattern. We examine current experiments such as KamLAND and MINOS to estimate the impact of the possible presence of such KK modes on the determination of the neutrino oscillation parameters and simultaneously obtain limits on the size of the largest extra dimension. We found that the presence of the KK modes do not essentially improve the quality of the fit compared to the case of the standard oscillation. By combining the results from KamLAND and MINOS, in the limit of a vanishing lightest neutrino mass, we obtain the stronger bound on the size of the extra dimension as ~ 0.9 \mu m at 99% CL. If the lightest neutrino mass turn out to be larger, 0.2 eV, for example, we obtain the bound ~ 0.2 \mu m. We also discuss the expected sensitivities on the size of the extra dimension for future experiments such as Double CHOOZ, T2K and NOvA.

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A ghostly particle given up for dead is showing signs of life.
Not only could this "sterile" neutrino be the stuff of dark matter, thought to make up the bulk of our universe, it might also help to explain how an excess of matter over antimatter arose in our universe.
Neutrinos are subatomic particles that rarely interact with ordinary matter. They are known to come in three flavours - electron, muon and tau - with each able to spontaneously transform into another.
In the 1990s, results from the Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos National Laboratory in New Mexico suggested there might be a fourth flavour: a "sterile" neutrino that is even less inclined to interact with ordinary matter than the others.
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