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|a CMS Collaboration
|e author
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|a Massachusetts Institute of Technology. Department of Physics
|e contributor
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|a Observation of the Z → ψ ℓ + ℓ - decay in pp collisions at v s = 13 TeV
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|b American Physical Society,
|c 2020-04-24T17:44:51Z.
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|z Get fulltext
|u https://hdl.handle.net/1721.1/124856
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|a This Letter presents the observation of the rare Z boson decay Z→ ψ ℓ + ℓ − . Here, ψ represents contributions from direct J/ψ and ψ ( 2 S ) → J / ψ X , 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 ( 2 S ) → J / ψ X contribution, the ratio of the branching fraction of the exclusive decay Z→ J / ψ ℓ + ℓ − to the decay Z→ μ + μ − μ + μ − within a fiducial phase space is measured to be B(Z→ J / ψ ℓ + ℓ − ) / B ( Z → μ + μ − μ + μ − ) = 0.67 ± 0.18 ( stat ) ± 0.05 ( syst ). ©2018
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|a en_US
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|a Article
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|t 10.1103/PhysRevLett.121.141801
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|t Physical review letters
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