Observation of the Z →ψ + - decay in pp collisions at s =13 TeV
This Letter presents the observation of the rare Z boson decay Z → ψlþl−. Here, ψ represents contributions from direct J=ψ and ψð2SÞ → J=ψX, lþl− is a pair of electrons or muons, and the J=ψ meson is detected via its decay to μþμ−. The sample of proton-proton collision data, collected by the CMS...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English English |
| Published: |
American Physical Society
2018
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/70337/ http://irep.iium.edu.my/70337/ http://irep.iium.edu.my/70337/ http://irep.iium.edu.my/70337/1/70337_Observation%20of%20the%20Z%20%E2%86%92%20%CF%88l%2Bl%E2%88%92%20Decay%20in%20pp%20Collisions_article.pdf http://irep.iium.edu.my/70337/2/70337_Observation%20of%20the%20Z%20%E2%86%92%20%CF%88l%2Bl%E2%88%92%20Decay%20in%20pp%20Collisions_scopus.pdf |
| Summary: | This Letter presents the observation of the rare Z boson decay Z → ψlþl−. Here, ψ represents
contributions from direct J=ψ and ψð2SÞ → J=ψX, lþl− is a pair of electrons or muons, and the J=ψ
meson is detected via its decay to μþμ−. 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 ψð2SÞ → J=ψX contribution, the ratio of the branching fraction of the exclusive decay Z → J=ψlþl−
to the decay Z → μþμ−μþμ− within a fiducial phase space is measured to be BðZ → J=ψlþl−Þ=
BðZ → μþμ−μþμ−Þ ¼ 0.67 0.18ðstatÞ 0.05ðsystÞ. |
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