Observation of the <i>Z</i> → ψ<i>l</i><SUP>+</SUP><i>l</i><SUP>-</SUP> Decay in <i>pp</i> Collisions at √<i>s</i>=13 TeV



Sirunyan, AM, Tumasyan, A, Adam, W, Ambrogi, F, Asilar, E, Bergauer, T, Brandstetter, J, Brondolin, E, Dragicevic, M, Eroe, J
et al (show 2260 more authors) (2018) Observation of the <i>Z</i> → ψ<i>l</i><SUP>+</SUP><i>l</i><SUP>-</SUP> Decay in <i>pp</i> Collisions at √<i>s</i>=13 TeV. PHYSICAL REVIEW LETTERS, 121 (14). 141801-.

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Abstract

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→J/ψℓ^{+}ℓ^{-} to the decay Z→μ^{+}μ^{-}μ^{+}μ^{-} within a fiducial phase space is measured to be B(Z→J/ψℓ^{+}ℓ^{-})/B(Z→μ^{+}μ^{-}μ^{+}μ^{-})=0.67±0.18(stat)±0.05(syst).

Item Type: Article
Uncontrolled Keywords: CMS Collaboration <a href="#n1">1</a>
Depositing User: Symplectic Admin
Date Deposited: 22 Feb 2019 15:12
Last Modified: 13 Oct 2023 12:07
DOI: 10.1103/PhysRevLett.121.141801
Open Access URL: https://doi.org/10.1103/PhysRevLett.121.141801
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3033282