occasional meanderings in physics' brave new world

Name:
Location: New Zealand

Marni D. Sheppeard

## Tuesday, May 27, 2008

### Neutrino08 Day 2c

H. Minakata continued with 2 possibilities, (i) $\theta_{13} > 3$deg, in which case conventional superbeams and megaton water detectors should work and (ii) small $\theta_{13}$, which would require new beam technologies, although liquid argon technology could change the situation. He promised to mention unconventional physics, but was forced to skip that section when the chair meanly rang the bell a little early. For varying E, he mentioned a possible 100 kiloton argon facility (3 or 4 times more sensitive than water Cherenkov detectors). For varying L, a test of CP violation would best use a low energy, short L setup.

Moving on to T2K, a 300km baseline Tokai to Kamioka project: I. Kato sketched the aim of observing $\theta_{23}$ and $\Delta m_{23}^{2}$ via muon neutrino disappearance with the help of the J-PARC accelerator. Achievable precision is apparently 0.01 in $\textrm{sin}^{2} 2 \theta$ and $< 10^{-4}$ for $\Delta m^{2}$. Installation and commissioning is on schedule: the LINAC at 181 MeV had good beam stability in Jan '07, the beam line tunnel was completed in Dec '06 and the main ring synchrotron is expected to be operational in 2009. After 5 years at SuperK at 0.75 kW they expect from 103 events (for 0.1 $\textrm{sin}^{2}$) to 10 events (for 0.01).

Despite the excellent IT support, R. Ray had to fight a Mac vs Bill Gates battle (which some people blamed on Fermilab) before commencing his talk on NOvA. This is a second generation NuMI beam line experiment requiring an accelerator upgrade to 700 kW beam power. A surface detector would be placed at Ash River, 810 km away. This requires a 6 storey, football field sized building on a site needing 40 ft of blasting in solid granite! A top cover of concrete/barite would shield the detector, which is a liquid scintillator in homemade highly reflective PVC cells. He stressed the importance of complementarity in experiments and comparisons of multiple results. For example, NOvA with Daya Bay and Chooz can determine if $\nu_{3}$ couples to the muon or tau neutrino (at 95% confidence). They expect a 36% event efficiency for electron neutrinos.

Future neutrino beams at J-PARC and Fermilab were discussed by Kajita and Saoulidou. For J-PARC, a Korean detector would give a 1000km+ baseline. Rubbia talked about proposed megaton detectors, for which there is a positive general consensus after reports in the US, Japan and Europe. In the 100 to 1000 kt range, one needs precise tracking and good calorimetric information. A feasibility study will be carried out 2008-2009. One interesting possibility is supernovae observation: the estimate is for 2 antineutrino events per year at 10 megaparsecs (with a 5 megaton water Cherenkov detector). Deep-TITAND (see hep-ex/0110005) is a 1km deep modular steel proposal.

As a pathologically punctual person, I have observed that the bell needs to be rung loudly before each session as chatting participants demonstrate their enthusiasm to their colleagues by pretending not to hear the bell.