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).

Observation of the Z →ψ + - Decay in pp Collisions at s =13 TeV / Sirunyan, A.M., Tumasyan, A., Adam, W., Ambrogi, F., Asilar, E., Bergauer, T., Brandstetter, J., Brondolin, E., Dragicevic, M., Ero, J., Escalante Del Valle, A., Flechl, M., Fruhwirth, R., Ghete, V.M., Hrubec, J., Jeitler, M., Krammer, N., Kratschmer, I., Liko, D., Madlener, T., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 121:14(2018), p. 141801.141801. [10.1103/PhysRevLett.121.141801]

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

Creanza D.;De Filippis N.;Di Florio A.;Iaselli G.;Pugliese G.;
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).
2018
Observation of the Z →ψ + - Decay in pp Collisions at s =13 TeV / Sirunyan, A.M., Tumasyan, A., Adam, W., Ambrogi, F., Asilar, E., Bergauer, T., Brandstetter, J., Brondolin, E., Dragicevic, M., Ero, J., Escalante Del Valle, A., Flechl, M., Fruhwirth, R., Ghete, V.M., Hrubec, J., Jeitler, M., Krammer, N., Kratschmer, I., Liko, D., Madlener, T., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 121:14(2018), p. 141801.141801. [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/11589/210424
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