Mismatch with Standard-Model Predictions Reaches 5 Sigma

Abstract

T ension was in the air on July 24 as members of the Muon g-2 Collaboration gathered in a conference room at the University of Liverpool, UK. The scientists had congregated to “unblind” their latest measurements of an anomalous property of the muon, an unstable particle that makes upmuch of the cosmic radiation that reaches Earth’s surface. When input into the computer, would the figures in two sealed envelopes reveal a match between the new analysis and a previous one? Or would the team have to announce that something had gone awry? There was a fear that values would be inconsistent with the collaboration’s earlier findings, says René Reimann, a physicist from the Johannes Gutenberg