Friday, June 11, 2010

Neutrino 2010

It is now June; school is getting out, and the summer conference season is starting. The big conference for neutrino physicists, Neutrino 2010 (it's held every 2 years) is next week, in Athens, Greece. About 530 neutrino physicists will gather for a week, to hear the latest results on everything neutrinos. Talks will cover a results from accelerators (Fermilab, CERN...) and non-accelerator experiments, along with the latest theory.

One hot topics is neutrino oscillations, whereby a neutrino from one flavor (like an electron neutrino) oscillates, over time turning into another flavor, like a muon neutrino. There are three different flavors, connected by three different mixing angles, which give a neutrinos propensity to turn into a different flavor. The three flavors have slightly different masses; the mass differences control how long the conversion takes. There is also a phase angle which, if non-zero, would allow charge-parity (CP) violation in neutrinos. This might help explain why the universe is all matter, with no visible antimatter. One way to study this is to shoot
a beam of neutrinos from an accelerator to a distant detector, and measure the oscillation probability. Another way to study oscillations is to use naturally occurring neutrinos. Neutrinos produced by nuclear reactions in the sun have plenty of time to oscillate before arriving at the earth; this is how neutrino oscillations were initially discovered. Or, one can use neutrinos produced in cosmic-ray air showers, which may oscillate as they pass through the earth on their way to a detector like IceCube.

A number of non-accelerator experiment are looking for a process called neutrinoless double beta decay, whereby an atomic nucleus decays, producing two electrons; the nuclear charge changes by two. For example, ^36Germanium decays into ^36Selenium, plus two neutrinos. This process can only happen if a neutrino is something called a "Majorana particle" which means that it is it's own antiparticle. In any case, the half-life for this process must be very long, well over 10^{22} years, so, one need a very large chunk of germanium to study this.

Neutrino astrophysics is also represented at the conference, with a couple of sessions including talks on high-energy astrophysical neutrinos. I will be giving an overview talk on radio-detection of neutrinos, covering ~ half a dozen experiments, including ARIANNA. It was a challenge to squeeze this all into a 15 + 5 minute (15 to speak, 5 for questions) talk.

I'm not looking forward to the long plane-flight to Athens; this will occupy a good chunk of the weekend.

I will try to post more frequently during the conference, both on conference life, and on new results.

No comments:

Post a Comment