Observation of the Z to psi l+ l- decay in pp collisions at sqrt(s) = 13 TeVстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 13 ноября 2018 г.
Аннотация:This Letter presents the observation of the rare Z boson decay Z →ψℓ+ℓ−. Here, ψ represents contributions from direct J/ψ and ψ(2S) → J/ψX, ℓ+ℓ− is a pair of electrons or muons, and the J/ψ meson is detected via its decay to μ+μ−. 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 ψ(2S) → J/ψX contribution, the ratio of the branching fraction of the exclusive decay Z →ψℓ+ℓ− to the decay Z →μ+μ−μ+μ− within a fiducial phase space is measured to be B(Z →ψℓ+ℓ−)/B(Z →μ+μ−μ+μ−)= 0.67 ± 0.18 (stat) ± 0.05 (syst).