Neutrinos Still Making a Massive Impact

摘要

The Physics Top Ten this period is once again a prism that refracts the stream of papers on neutrino physics, now dominating our table. Half the papers are on solar neutrinos (#2, #3, #7, #9) and atmospheric neutrinos (#4). This intense activity is being driven by the new-found ability of physicists to capture and analyze neutrinos in worthwhile numbers, compared to a trickle of events a decade ago. Furthermore, modern experiments are revealing spectacular new physics, with neutrinos spontaneously transforming type while in flight. Paper #9 is a classic in solar neutrino astronomy. This paper asks, What is the present rate of neutrino production in the solar core? For decades researchers could only detect the solar neutrinos produced in small side reactions to the main proton-proton fusion reactions. The Gallex experiment changed all that, with the direct detection of proton-proton reactions. In Gallex, the solar neutrinos cause inverse beta decay in ~(71)Ga to ~(71)Ge, and the number of ~(71)Ge atoms produced gives the solar neutrino flux. Gallium detection was a huge leap forward because 93% of solar neutrinos are only detectable through this channel.