Thursday, June 24, 2010

Neutrino 2010 - conference report

Neutrino 2010 was an interesting conference. There were no earthshaking new results, but there was steady progress on many fronts.

The most interesting new results came from the MINOS and MiniBoone experiments. These are both detectors that observe neutrinos produced by an accelerator at Fermilab, near Chicago. Both experiments are studying neutrino oscillations, whereby a neutrino produced with one flavor (electron, muon or tau neutrino) oscillates as it travels from the accelerator to the detector.

MINOS has observed a possible difference between how neutrinos and antineutrinos oscillate. If correct, this would be very surprising, signalling a big difference between matter and antimatter. Although this result got significant publicity, apparently due to a Fermilab press release, the difference was not statistically large, and almost everyone at the conference was happy to treat it as a likely statistical fluctuation, pending more data. The other anomaly, from MiniBoone is harder to characterize, but is also likely a statistical fluctuation.

Two other popular topics were searches for neutrinoless double beta decay, and progress toward enormous (100,000-500,000 ton detector) next generation detectors.

In neutrinoless double beta decay, a nucleus changes it's atomic number by two (i.e. germanium decays to selenium, or xenon to barium), emitting two electrons and no neutrinos. This is only possible if a neutrino can act as it's own antiparticle, so this would be a major discovery. If this process occurs, it is very rare, with a half live of well over 10**20 (10 to the 20th power) years. So, these experiments must monitor large quantities (typically 100 pounds to 1 ton) of material for long periods, with a sensitivity to observe even a handful of decays. This is not easy. We heard 6 talks on neutrinoless double beta decay, discussing a wide variety of possible methods.

Over the past two years, there has been considerable progress toward a very large detector to make precision measurements of neutrino oscillations. The U.S. version would be located in DUSEL, the Deep Underground Science and Engineering Laboratory, which is proposed to be built in an old gold mine in South Dakota. The Japanese are also pursuing a similar project on an island between Japan and South Korea (the location is chosen to be the optimal distance from the Japan Hadron Facility accelerator), and the Europeans are considering several projects at diverse sites.

My talk, on radiodetection of neutrinos, went well, and seemed well received. It was a tough talk to prepare, since I had to introduce the concept, and also cover experiments looking for neutrino interactions in the moon, and two types of experiments looking for neutrino interactions in Antarctic ice (including, of course, ARIANNA). I also had a chance to talk to a number of people who are interested in ARIANNA.

Although Athens is a very interesting city, June is not the optimal time for a visit. They were having a heat wave during the conference, and temperatures were in the high 90's or low 100's (depending on which source you looked at), and it was also fairly humid. Worse, there was a 3-day metro (subway) strike during the conference. This was quite disruptive, since many of us were taking the metro between our hotels and the conference center. Of course, during the strike, the busses were jammed past capacity, and taxis were hard to get.

This strikes was not an isolated incident; more strikes are planned to protest government cutbacks due to the budget deficit and the economic conditions imposed by the European/IMF bailout. The threat of strikes has trimmed the tourist trade (it is down about 15% according to what I've read), and Athens seemed less crowded than usual. My hotel was not overly full, and a fair fraction of the residents were neutrino physicists. My flight to Greece was half empty, and there seemed to be a number of parked Olympic Air planes at the Athens airport.

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