Particle Doppelganger of Neutral Pion Baffles Physicists
At the SuperKEKB accelerator, electrons collide with positrons, and among the debris, B-mesons are found. These heavy particles live briefly and break apart into lighter ones. Recently, the Belle II detector recorded a suspiciously high number of cases where a B-meson transforms into a K-meson (kaon) and something invisible—2.7 sigma more than expected.