Over nearly half a century, neutrinos have revealed much about the workings of a variety of astronomical objects including the sun, supernovae, and the earth. The pioneering experiment of Ray Davis revealed that the measured rate of neutrinos coming from the sun was less than expected. His experiment only measured one type of neutrino, which was the same type as those produced in the sun. More than 30 years later the Sudbury Neutrino Observatory (SNO) measured the rate of all types of neutrinos coming from the sun, obtaining a number that matched expectations. This not only confirmed our model of the sun, but was also consistent with the theory of neutrino oscillations, where neutrinos produced as one type are detected as another, which had developed over the intervening years. The confirmation of neutrino oscillations revealed that neutrinos have mass, but we still do not know how to incorporate that mass into the standard model of particle physics, as a neutrino may be either a Dirac neutrino (like the other particles) or a Majorana neutrino (where changing the handedness of the neutrino also changes it from particle to anti-particle). Recently SNO published their final results, which were the most precise test of our understanding of the sun to date. The SNO detector is currently being converted into SNO+, which will be able to test other aspects of the sun's working and will test the Majorana versus Dirac nature of the neutrino. In this talk I will describe results from SNO and the prospects for the SNO+ experiment.
Argonne Physics Division Seminar Schedule