Rare Particle Decay Challenges Standard Model, Hints at New Physics

(EPFL, March 20, 2025)

EPFL scientists have observed the rarest particle decay ever recorded. Specifically, they have observed the decay of a kaon, a particle made from a quark and an antiquark, into a pion and a neutrino-antineutrino pair for the first time, challenging the Standard Model of physics. This rare event, detected by a team led by Dr. Radoslav Marchevski from CERN, occurred at a rate 50% higher than predicted, potentially hinting at further discoveries beyond the current model of physics. The breakthrough came from analyzing extensive data from CERN’s NA62 experiment from 2016 to 2022 and using a new neutrino-tagging technique. This method, a joint effort between EPFL and Aix-Marseille University, allows scientists to accurately identify neutrinos and trace them back to their origin with unprecedented precision. This advancement not only marks a significant milestone in neutrino research but also promises to deepen our knowledge of neutrino interactions and their crucial role in the cosmos.