21 October 2015, 11:00, BLTP Blokhintsev conference hall (4th floor). Seminar QUANTUM FIELD THEORY

Chitta Ranjan Das "Non-standard interactions and Sterile Neutrino from Solar data"

Abstract

Can non-standard interactions (NSI) (neutrino decay in solar matter?) or sterile neutrino may solve the tension between the observed flatness of the SuperKamiokande electron spectrum and its LMA (large mixing angle) prediction.

It has been known for some time that the well established LMA (large mixing angle) solution to the observed solar neutrino deficit fails to predict a flat energy spectrum for SuperKamiokande as opposed to what the data indicates. We investigate the possible solution to these inconsistencies with non standard neutrino interactions, assuming that they come as extra contributions to the νανβ and ναe vertices that affect both the propagation of neutrinos in the sun and their detection. We find that, among the many possibilities for non standard couplings, only the diagonal imaginary ones lead to a solution to the tension between the LMA predictions and the data, implying neutrino instability in the solar matter. Unitarity requirements further restrict the solution and a neutrino decay into an antineutrino and a majoron within the sun is the one favoured. On the other hand the neutrino decay probability into an antineutrino and a majoron, as in the case of the sun, is too small to be observed as a direct consequence of NSI. We will also show NSI studied in the context of supernova. Also it is found that a sterile neutrino in the context of an extension to the standard electroweak model, which is quasi degenerate with the active ones with Δm241 = 10-5 eV2 and mixing sinθ14=0.04 provides a suitable improvement to the LMA data fits.

We also outline future collaborative neutrino physics projects in BLTP.