Mass hierarchy determination using atmospheric neutrinos for small and vanishing \theta_13

by Raj Gandhi (Harish-Chandra Research Institute, Allahabad)

Friday 23 May 2008, 14:00 → 15:00 Europe/Zurich

TH Theory Conference Room (CERN)

We study the possibility of determining the neutrino mass hierarchy for vanishing or very small $\theta_{13}$ using upward moving atmospheric neutrinos. For such values of $\theta_{13}$, long pathlengths through the earth, and energies of a few GeV, we show that the muon neutrino survival probability is almost independent of the matter potential. It however, contains hierarchy sensitive terms which can be exploited in a large atmospheric neutrino detector. After dicussing the physics aspects of the small or zero mixing angle sitiuation, to demonstrate the feasibility of this method, we present results of realistic studies of the sensitivity in three different proposed large-mass future detectors of atmospheric neutrinos -- a 100 kT Iron Calorimeter detector, a megaton Water Cerenkov detector and a 100 kT Liquid Argon detector. In cognizance of the fact that it is imperative to have good ( i.e about 2%) precision in $|\Delta_{31}|$ to obtain a statistically significant hierarchy sensitivity using this method, we note that such precision is possible with proposed contemporaneous wide-band beams.

Slides gandhi_th13_talk.pdf