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EnglishThis Letter presents the observation of the rare Z boson decay Z -> psi l(+)l(-). Here, psi represents contributions from direct J/psi and psi(2S) -> J/psi X, l(+)l(-) is a pair of electrons or muons, and the J/psi meson is detected via its decay to mu(+)mu(-). 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 psi(2S) -> J/psi X contribution, the ratio of the branching fraction of the exclusive decay Z -> J/psi X, l(+) l(-) to the decay Z -> mu(+)mu(-)mu(+)mu(-) within a fiducial phase space is measured to be B(Z -> J/psi X, l(+) l(-))/B(Z -> mu(+)mu(-)mu(+)mu(-)) = 0.67 +/- 0.18(stat) +/- 0.05(syst).
| Titolo: | Observation of the Z -> psi l+ l- decay in pp collisions at sqrt(s) = 13 TeV |
| Autori: | |
| Data di pubblicazione: | 2018 |
| Stato di pubblicazione: | Pubblicato |
| Rivista: | |
| Abstract: | This Letter presents the observation of the rare Z boson decay Z -> psi l(+)l(-). Here, psi represents contributions from direct J/psi and psi(2S) -> J/psi X, l(+)l(-) is a pair of electrons or muons, and the J/psi meson is detected via its decay to mu(+)mu(-). 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 psi(2S) -> J/psi X contribution, the ratio of the branching fraction of the exclusive decay Z -> J/psi X, l(+) l(-) to the decay Z -> mu(+)mu(-)mu(+)mu(-) within a fiducial phase space is measured to be B(Z -> J/psi X, l(+) l(-))/B(Z -> mu(+)mu(-)mu(+)mu(-)) = 0.67 +/- 0.18(stat) +/- 0.05(syst). |
| Handle: | http://hdl.handle.net/11368/2929897 |
| Digital Object Identifier (DOI): | 10.1103/PhysRevLett.121.141801 |
| URL: | https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.141801 |
| Appare nelle tipologie: | 1.1 Articolo in Rivista |
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| File | Descrizione | Tipologia | Licenza | |
|---|---|---|---|---|
| PhysRevLett.121.141801.pdf | Publisher-Version |  | Open Access Visualizza/Apri |
http://hdl.handle.net/11368/2929897
