Observation of the very rare {\ensuremath{\Sigma}}+{\textrightarrow}p{\ensuremath{\mu}}+{\ensuremath{\mu}}- decay

Physical Review Letters. 2025. Vol. 135. No. 5. P. 051801.

Ratnikov F., Boldyrev A.

The first observation of the Σ+ →𝑝⁢𝜇+⁢𝜇− decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 5.4  fb−1, collected with the LHCb detector at a center-of-mass energy of 13 TeV. A yield of 237±16  Σ+→𝑝⁢𝜇+⁢𝜇− decays is obtained, where the uncertainty is statistical only. A branching fraction of (1.08±0.17)×10−8 is measured, where the uncertainty includes statistical and systematic sources. No evidence of resonant structures is found in the dimuon invariant-mass distribution. All results are compatible with standard model expectations. This represents the rarest decay of a baryon ever observed.

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Keywords: физика элементарных частиц, rare decays, Experimental Particle Physics, редкие распады

Publication based on the results of: Development of theoretical foundations and methods of generative artificial intelligence and their application to heterogeneous domain area (2025)