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T. Schwetz: Reactor Anomaly, Theta_13, and Sterile Neutrinos

March 17, 2011

Let me try to summarize the talk of Thomas Schwetz in few lines.
For the first time a neutrino model that includes sterile neutrinos provides a better fit to the global world data on neutrino oscillations than the conventional three active neutrino model.

This is going to be a change of paradigma, and it’s one of the highlights of
the conference.

Furthermore the model with two sterile neutrinos is definitely better than the model with just one. More steriles or other exotic ingredients like non standard neutrino interactions or CPT violation seem to be no more necessary.

What happened to generate such a change? The main ingredient has been provided by Thierry Lasserre and his collaborators (see the dedicated topic). With an impressive effort of some years they re-computed from scratch the detailed flux of reactor antineutrinos. They ended up with an estimated antineutrino flux about 3% higher than previous estimates. This new computation transformed the several reactor antineutrino oscillation experiments at short baselines, performed in the 80’s, from evidences against steriles (no deficit observed of the expected antineutrino flux) to evidences in favor of sterile neutrinos (3% deficit of the expected flux).

Piece by piece the evidences in favor of sterile neutrinos are not that great (they are considered anomalies rather than evidences), but the overall picture now favors sterile neutrinos. These ideas are also further elaborated by C. Giunti in a talk of  Thursday morning (see transcript by L.Merlo below). Future experimental  programs needed to provide better information on sterile neutrinos have been discussed by Geoff Mills and Carlo Rubbia again on Thursday morning. Reports on those talks are coming soon.

(Posted by M.Mezzetto)

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