Results from the Neutral Current Detector Phase of the Sudbury Neutrino Observatory

Ryan Martin
Queen's University


In this talk, I will present the latest published results from the Sudbury Neutrino Observatory (SNO). This Heavy-Water (D20) Cerenkov detector was designed to resolve the solar neutrino problem; since Ray Davis' experiment in the 1960s, there had been a discrepancy between the measured solar neutrino flux and that predicted by the solar model. The SNO experiment conclusively showed in 2001 that solar neutrinos, produced in the electron flavour, transform into muon and tau flavours on their way to earth. The detector was able to measure the electron flavour flux through a charged-current reaction, whereas the total flux of neutrinos was measured independently through a neutral-current reaction that produced a neutron. The SNO experiment was performed in three phases defined by different ways of detecting the neutron. In the first phase, the neutrons were detected by capture on deuterium, in the second phase, two tons of salt (NaCl) were added to exploit the high cross-section for neutron capture on 35-Cl, and finally, in the third phase, 40 proportional counters (filled with 3-He) were deployed. My talk will start with an introduction to solar neutrino physics before introducing the SNO experiment and the results from the salt phase. I will then talk about the analysis of the proportional counter data and the results from that phase.