Juan de Dios Zornoza: ANTARES Results
Neutrinos have some advantages as messengers for neutrino astronomy: they do not interact with the CMB background among others. They are expected to be produced in the interaction of high-energy nucleons with matter or radiation. Gamma rays are also produced in this scenarios. So there is complementarity in the two ways of looking at the cosmos with high-energy gamma and neutrinos.
The detection principle of neutrinos in Antares is based on a signature of the cherenkov light emitted by muons produced in CC interactions. The good angular resolution allows one to speak of a true telescope concept.
The speaker made some comments on using water versus ice. They both provide large volumes to work with. Oceans have a large scattering length, so better angular resolution, and a weaker depth-dependence of optical parameters, and a changeable detector geometry. Ice on the other hand has larger absorption lengths, and offer absence of bioluminoscence, 40K backgrounds, and easier deployment. But ice is confined in the antarctica, and we need a northern hemisphere-based detector for complete sky coverage. From the south pole you see the northern emisphere, and viceversa from Antares.
Backgrounds are muons produced by cosmic rays, and atmospheric neutrinos. Antares is made up by 885 PMT tubes in 12 lines, separated by about 60 meters. The detector was completed in 2008 and has been working smoothly. The main element is the photomultiplier, and then there are optical beacons that allow timing calibration and water properties measurements.
Antares is not designed for oscillation measurements, but they can do it. The trick is to go to very low energy, where the detector is not optimized. One does not use the angular information so single-line events are usable, making the analysis possible.
For point-source searches, the selection is based on zenith angle and other quality cuts. They have 3058 events in 2007-2010 data. There are no significant clustering, and they put limits in the flux. Limits were also shown for diffuse cosmic fluxes.
In summary, neutrino astronomy is becoming a powerful tool for astrophysics and particle physics. Antares is taking data, and has already produced a rich physics output in a number of topics. The technical success of antares paves the way for larger endeavour.