Bilki, Burak., ve diger2019-03-282019-03-282018PHYSICAL REVIEW LETTERS 121, 141801 (2018)1079-71140031-9007https://doi.org/10.1103/PhysRevLett.121.141801This Letter presents the observation of the rare Z boson decay Z???+??. Here, ? represents contributions from direct J/? and ?(2S)?J/?X, ?+?? is a pair of electrons or muons, and the J/?meson is detected via its decay to ?+??. The sample of proton-proton collision data, collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponds to an integrated luminosity of 35.9??fb?1. The signal is observed with a significance in excess of 5 standard deviations. After subtraction of the ?(2S)?J/?X contribution, the ratio of the branching fraction of the exclusive decay Z?J/??+?? to the decay Z??+???+?? within a fiducial phase space is measured to be B(Z?J/??+??)/B(Z??+???+??)=0.67±0.18(stat)±0.05(syst).enRare decaysLEPTONSW & Z bosonsHadron collidersQUARKONİAArticle10.1103/PhysRevLett.121.1418012-s2.0-8505466659430339440Q1WOS:000446406900001Q1