Minutes from March 4 Meeting

Mayda Velasco gave a talk about the NUMI on and off-axis beams, considering the differences between positive and negative horn polarity (i.e. making a mostly neutrino or a mostly antineutrino beam). Bottom lines for a NUMI off-axis beam, when horns and target are in nominal configuration:

For on and off axis, numu event rates from 1 to about 5 GeV are about 3 times the numubar rates
For off axis, the fractional background from (nu_e+nubar_e) is the same between numu and numubar running: this is because the backgrounds are mostly from muon decay at 2GeV.
the numu background in the numubar beam is about 10%, while the numubar background in the numu beam is only about 1%.

http://lotus.phys.nwu.edu/~mvelasco/nu_bar/off_axis.ps

Andre DeGouvea gave a talk about the sensitivity to matter effects, Ue3^2, and CP violation, using the fluxes assumed above. Where relevant Andre, Gabriela and Mayda assumed there would be both an on-axis and an off axis measurement.
The running assumptions are: off and on axis detector 40kton-years for neutrino running, and 80 kton-years for antineutrino running. The efficiency and background assumptions correspond to segmented minos off-axis (so very little NC background), and minos on-axis (more NC background). The assumption is that the two detectors have the same mass, so given that MINOS is 5kton, if you had an off-axis detector at 5kton and a proton driver upgrade (to gain a factor of 4) then you would be running for 2 years neutrino mode, 4 years antineutrino mode. If you had the off axis detector with more mass, that counts for more since most of the statistical power for looking at numu to nue comes from the off-axis beam.
Plots were shown for three different values of solar mass splitting (dm_12^2), since for these three regions the physics reach is different.

solar delta m^2 at 10^-7
in this case, we can't do cp violation, we can at best measure theta13 and measure matter effects
http://lotus.phys.nwu.edu/~mvelasco/nu_bar/andre/hierarchy.ps
Shows that the chi2 of the fit is if you assume 2 different signs for the matter effects...
solar delta m^2 at 10^-4
so KamLAND can measure it precisely,
http://lotus.phys.nwu.edu/~mvelasco/nu_bar/andre/measure2.ps
http://lotus.phys.nwu.edu/~mvelasco/nu_bar/andre/ue3_vs_delta.ps
http://lotus.phys.nwu.edu/~mvelasco/nu_bar/andre/ue3_vs_dm13_2.ps
solar delta m^2 between 2 and 10x10^-4,
where KamLAND can only say that it's large, but can't measure it precisely. CHOOZ limits this to somewhere around 7x10^-4. For this range of parameter space things are actually tricky, because now there will be a large uncertainty on the actual value of dm12^2, and without another experiment to measure it (say a mini-kamland experiment near to one reactor, or maybe the MiniBooNE detector but deeper undergrond, looking at neutrinos from the Zion reactor )
http://lotus.phys.nwu.edu/~mvelasco/nu_bar/andre/ue3_vs_dm12.ps

Steve Geer made the suggestion that for given values of ue3^2, one should also include the measurement that could be made by JHF to SuperK--as a constraint--the different energy could be an important constraint in some (if not most) of the above plots.

Deborah Harris

Last modified: Mon Mar 4 15:39:45 CST 2002