@article{59adc1d1d289485a89e39f0fa8112271,
title = "Observation of the Rare Decay of the η Meson to Four Muons",
abstract = "A search for the rare Formula Presented 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 Formula Presented. A signal having a statistical significance well in excess of 5 standard deviations is observed. Using the Formula Presented decay as normalization, the branching fraction Formula Presented 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.",
author = "{CMS Collaboration} and A. Hayrapetyan and A. Tumasyan and W. Adam and Andrejkovic, {J. W.} and T. Bergauer and S. Chatterjee and K. Damanakis and M. Dragicevic and {Escalante Del Valle}, A. and Hussain, {P. S.} and M. Jeitler and N. Krammer and D. Liko and I. Mikulec and J. Schieck and R. Sch{\"o}fbeck and D. Schwarz and M. Sonawane and S. Templ and W. Waltenberger and Wulz, {C. E.} and Darwish, {M. R.} and T. Janssen and {Van Mechelen}, P. and Bols, {E. S.} and J. D{\textquoteright}Hondt and S. Dansana and {De Moor}, A. and M. Delcourt and {El Faham}, H. and S. Lowette and I. Makarenko and A. Morton and D. M{\"u}ller and Sahasransu, {A. R.} and S. Tavernier and M. Tytgat and {Van Putte}, S. and D. Vannerom and B. Clerbaux and {De Lentdecker}, G. and L. Favart and D. Hohov and J. Jaramillo and A. Khalilzadeh and K. Lee and M. Mahdavikhorrami and A. Malara and S. Paredes and A. Moraes",
note = "Publisher Copyright: {\textcopyright} 2023 CERN, for the CMS Collaboration.",
year = "2023",
month = sep,
day = "1",
doi = "10.1103/PhysRevLett.131.091903",
language = "English",
volume = "131",
journal = "Physical Review Letters",
issn = "0031-9007",
number = "9",
}