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).

Sirunyan, A., Tumasyan, A., Adam, W., Ambrogi, F., Asilar, E., Bergauer, T., et al. (2018). Observation of the Z →ψ + - Decay in pp Collisions at s =13 TeV. PHYSICAL REVIEW LETTERS, 121(14) [10.1103/PhysRevLett.121.141801].

Observation of the Z →ψ + - Decay in pp Collisions at s =13 TeV

Dinardo M. E.;Ghezzi A.;Govoni P.;Malberti M.;Massironi A.;Moroni L.;Paganoni M.;Ragazzi S.;Tabarelli De Fatis T.;Gerosa R.;Lucchini M. T.;De Guio F.;
2018

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).
Articolo in rivista - Articolo scientifico
Standard Model
English
2018
121
14
141801
none
Sirunyan, A., Tumasyan, A., Adam, W., Ambrogi, F., Asilar, E., Bergauer, T., et al. (2018). Observation of the Z →ψ + - Decay in pp Collisions at s =13 TeV. PHYSICAL REVIEW LETTERS, 121(14) [10.1103/PhysRevLett.121.141801].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/309543
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