LHCb finds evidence for the decay B0 to mu+ mu-, with improved B0s measurement

The LHCb collaboration reports evidence that the neutral B⁰ meson decays into a positively and negatively charged muon, alongside more precise measurements of the corresponding B⁰s decay. These dimuon decays are exceptionally rare: they occur through processes strongly suppressed in the Standard Model of particle physics, rather than through its more common direct interactions. That rarity makes them useful tests of the theory and sensitive probes for possible contributions from unknown particles or forces.

The B⁰ result marks progress in observing a decay that is harder to detect than its B⁰s counterpart. “Evidence” indicates that the observed signal supports the decay’s existence, while stopping short of the stronger statistical standard conventionally required to claim a discovery. The improved B⁰s measurements refine the experimental picture of a related rare process, enabling more stringent comparisons with theoretical predictions. Together, the findings advance two complementary tests of particle physics: establishing the less frequently observed B⁰ channel and sharpening knowledge of the B⁰s channel. The supplied information does not give the measured decay rates, statistical significance, or data sample, so the numerical size and precision of the results cannot be assessed here.