Monday, January 23, 2006

Neutrinos on Ice

In an earlier post, Matthew talked about the AMANDA and IceCube neutrino detectors based at the South Pole, which utilize the antarctic ice shield both as a shielding against cosmic radiation and as the medium for a giant Cherenkov-type detector.

In the most recent issue of Physical Review Letters, members of the AMANDA collaboration report on the limits on neutrino cross sections at ultra-high energies that result from the AMANDA events seen so far. Since the event rate in the detector depends on both the cross section and the flux (both of which are unknown) they can only exclude cross section/flux pairs, but by looking separately at down-going neutrinos (which have crossed only the atmosphere and ice shield) and up-going neutrinos (which have passed through the body of the earth, more than one interaction length at the energies they consider), the authors are able to impose upper limits on the cross section at very high energies and an absolute upper bound on the neutrino flux.

I rarely envy experimentalists, but this Symmetry magazine article about AMANDA, IceCube, ANTARES and NESTOR (two rival neutrino telescopes using the deep sea instead of the Antarctic ice) makes me feel just a little jealous of the opportunities they can get to go to such amazing and distant places.