Observation of the Rare Decay of the η Meson to Four Muons

Physical Review Letters 2023
Kārlis Dreimanis, Antra Gaile, Guntis Pikurs, Andris Potrebko, Markus Seidel, Viesturs Veckalns, CMS Collaboration

A search for the rare η→μ+μ-μ+μ- double-Dalitz decay is performed using a sample of proton-proton collisions, collected by the CMS experiment at the CERN LHC with high-rate muon triggers during 2017 and 2018 and corresponding to an integrated luminosity of 101  fb-1. A signal having a statistical significance well in excess of 5 standard deviations is observed. Using the η→μ+μ- decay as normalization, the branching fraction B(η→μ+μ-μ+μ-)=[5.0±0.8(stat)±0.7(syst)±0.7(B2μ)]×10-9 is measured, where the last term is the uncertainty in the normalization channel branching fraction. This work achieves an improved precision of over 5 orders of magnitude compared to previous results, leading to the first measurement of this branching fraction, which is found to agree with theoretical predictions.

DOI
10.1103/PhysRevLett.131.091903
Hyperlink
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.091903

The CMS Collaboration, A.Hayrapetyan, K.Dreimanis, A.Gaile, G.Pikurs, A.Potrebko, M.Seidel, V.Veckalns ... [et al.]. Observation of the Rare Decay of the η Meson to Four Muons. Physical Review Letters, 2023, Vol. 131, No. 9, Article number 091903. ISSN 0031-9007. e-ISSN 1079-7114. Available from: doi:10.1103/PhysRevLett.131.091903

Publication language
English (en)