April 16 Minutes

Matter Effects Discussion

Andrea Romanino lead a discussion about matter effects in the case that LSND is confirmed. If this is the case, then the resonance energy corresponding to the largest mass difference is 1-3TeV*(delta m^2 LSND/1eV^2), so matter effects would be invisible. The only matter effects that might appear are in transitions between nu_e and nu sterile. The other matter effect that would arise would be that between nu_e and nu_mu, but with an energy 0.1->0.3GeV (delta m^2 solar/10^-4eV^2). But since that transition is already expected to be at a large angle (theta_12 might be almost maximal), the matter effects would only serve to make the theta-12 effective a little smaller, not magnify it. However, if LSND is confirmed and we do think there is a sterile neutrino, then there is actually less of an imperative to measure the sign of the second largest mass splitting, since half the models predict one sign, and half the models predict the other sign.

Super-MINOS studies

We also talked about Larry Wai's superbeam study, using a fine-grained version of the MINOS detector, the NUMI-Medium Energy Beam, and 10kton-years, going towards SLAC. Bob Bernstein looked at the precision one would achieve with 10kton years and a baseline of 2800km--one could presumably get about a 2% measurement of sin^2 2 theta_23, so one might be able to say we had large as opposed to maximal mixing. Romanino and Barenboim pointed out that it would be important theoretically to be able to distinguish between large and maximal mixing.

Other business

We didn't have time to discuss the outline that Debbie started putting together about the detector R&D report that is due in May, a link to the very very preliminary outline can be found here.
Deborah Harris
Last modified: Fri Apr 20 15:22:52 CDT 2001