Glimpses of the “gallium anomaly” were first seen in the mid-1990s, but it was first clearly discovered and stated in 2007 by neutrino physicist Carlo Giunti of Italy. The problem is simple to state but potentially very important: about 20% fewer electron neutrinos were seen to be captured by gallium nuclei than expected.
Solving the gallium anomaly: New calculation may explain neutrino shortfall without invoking new particles
