Observation of the Z → ψ ℓ + ℓ − decay in pp collisions at √s = 13 TeV
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Type :
Article
Publication Status :
Published
Access :
openAccess
Abstract
This Letter presents the observation of the rare Z boson decay Z→ψ + -. Here, ψ represents contributions from direct J/ψ and ψ(2S)→J/ψX, + - 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/ψ + - to the decay Z→μ+μ-μ+μ- within a fiducial phase space is measured to be B(Z→J/ψ + -)/B(Z→μ+μ-μ+μ-)=0.67±0.18(stat)±0.05(syst).
Source :
Physical Review Letters
Date :
2018-10-04
Volume :
121
Issue :
14
Publisher :
American Physical Society
URI
http://hdl.handle.net/10679/6193https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.141801
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