Observation of the Rare Decay of the 𝜂 Meson to Four Muons
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 in 2017-2018 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 five orders of magnitude compared to previous results, leading to the first measurement of this branching fraction, which is found to agree with theoretical predictions.
- Research Organization:
- Princeton University, NJ (United States)
- Sponsoring Organization:
- USDOE
- Contributing Organization:
- CMS Collaboration
- Grant/Contract Number:
- SC0007968
- OSTI ID:
- 3011028
- Alternate ID(s):
- OSTI ID: 2341242
OSTI ID: 2403066
OSTI ID: 1997838
OSTI ID: 1988459
- Journal Information:
- Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 9 Vol. 131; ISSN 1079-7114; ISSN 0031-9007
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English