occasional meanderings in physics' brave new world

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Location: New Zealand

Marni D. Sheppeard

Tuesday, May 27, 2008

Neutrino08 Day 2a

J. Raaf was first up today with a report on Super Kamiokande, a 50 kiloton water Cherenkov detector under 1km of rock. Solar neutrinos: the focus was on phase III (mid 2006 to late 2008) results using 2 data sets, (i) full (E > 6.5 MeV) and (ii) radon reduced (E > 5 MeV), which are expected to achieve a 60cm elastic scattering vertex resolution. Phase II results showed no correlation with solar activity nor any day-night asymmetry (measured at -0.063 with larger errors). Atmospheric: a re-analysis of phase I data looking for exotic effects can exclude many models.

H. Gallagher represented MINOS, a long baseline experiment based at Fermilab and a Minnesota mine 735km away. Analyses of both charged and neutral current events were done blind. There are about $10^{18}$ protons hitting the target per day at the main injector, and 92.9% of neutrinos produced are muon $\nu$. Charged case: new run 1 and 2 results indicate a $\Delta m^{2} = 2.43 \times 10^{-3} eV^{2}$ and $\textrm{sin}^{2} 2 \theta = 1.00$, or rather $> 0.90$ at 90% confidence. Neutral case: depletion of neutral events is expected in the far detector but no evidence for it was found, the bound being 17% in a 0-120 GeV range. Neutrino decoherence is disfavoured $5.7 \sigma$.

OPERA is a 730km baseline (from CERN) emulsion tracking device which hopes to observe $\nu_{\tau}$ events. Muon neutrino flux is optimized with L/E = 43 km/GeV. Rosa described the detector modules, constructed of scintillator strip target modules embedded in 31 walls, each built from up to 3000 custom bricks of layered emulsion and Pb sheets. See 0804.1985. The short 2007 run saw 38 triggered candidate events with (at the end) 64060 bricks. With a high intensity beam at about 200 events per week, it is expected that the new run (starting around June 16) will see 1.2 $\nu_{\tau}$ events.

a quantum diaries survivor said...

I know the OPERA experiment well, having been in a thesis committee with a student graduating on that.

OPERA is revolutionary in one aspect - the detector gets disassembled day by day as bricks are identified which have a potential signal in them, and removed from the assembly. A bit like the central computer of A Space Odyssey, if you know what I mean.

Cheers,
T.

May 28, 2008 1:49 AM
Glenn HS said...

I really appreciate these blog entries, and I think you're doing a great job in general. One question, though: when summarizing experimental talks, why do you give the best fit values and not the uncertainties? (E.g., MINOS "$\Delta m^{2} = 2.43 \times 10^{-3} eV^{2}$", KamLAND "\$\Delta m^2 = 7.59 \times 10^{-5} (eV)^{2}".) The real news from these experiments is the reduction in the error bars since their last reports.

Loving the blog anyway. Thanks!
-G.

May 28, 2008 4:15 AM
Kea said...

Sorry Glenn! I'm just a lazy (and very tired) theorist! I'll try to include such important information future posts.

May 28, 2008 6:15 AM