A first observation of the rare decay η→μ+μ-e+e- is reported by the CMS Collaboration at the CERN LHC. The result is based on a proton-proton collision data sample at s = 13.6 TeV corresponding to an integrated luminosity of 38.0 fb-1, acquired in 2022 using a high-rate dimuon trigger. Using the η→μ+μ-γ decay channel for normalization, the branching fraction is measured to be B(η→μ+μ-e+e-) = (2.4±0.8)×10-6, with the uncertainty including statistical and systematic sources as well as the B(η→μ+μ-γ) uncertainty. This result is about a factor of 3 smaller than the existing limit and is consistent with recent theoretical predictions.
Observation of the Rare Decay η → μ + μ − e + e −
Abbrescia, M.;Barbieri, M.;Buonsante, M.;Colaleo, A.;De Palma, M.;Elmetenawee, W.;Generoso, L.;Louka, M.;Mastrapasqua, V.;My, S.;Nenna, F.;Nuzzo, S.;Pellecchia, A.;Pompili, A.;Radogna, R.;Stamerra, A.;Troiano, D.;Venditti, R.;Zaza, A.;D'Anzi, B.;
2026-01-01
Abstract
A first observation of the rare decay η→μ+μ-e+e- is reported by the CMS Collaboration at the CERN LHC. The result is based on a proton-proton collision data sample at s = 13.6 TeV corresponding to an integrated luminosity of 38.0 fb-1, acquired in 2022 using a high-rate dimuon trigger. Using the η→μ+μ-γ decay channel for normalization, the branching fraction is measured to be B(η→μ+μ-e+e-) = (2.4±0.8)×10-6, with the uncertainty including statistical and systematic sources as well as the B(η→μ+μ-γ) uncertainty. This result is about a factor of 3 smaller than the existing limit and is consistent with recent theoretical predictions.File in questo prodotto:
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