Anomalous experiment result suggests physicists may need to rethink the humble neutrino

Either the Standard Model needs tweaking – or we have a new fundamental particle.

Located deep underground at the Baksan Neutrino Observatory in the Caucasus mountains in Russia, the completed two-zone gallium target, at left, contains an inner and outer tank of gallium, which is irradiated by an electron neutrino source. Credit: A.A. Shikhin.