Observation of the Z → ψl + l − Decay in pp Collisions at ffiffi s p = 13 TeV

• Main Authors: The CMS Collaboration (Author), Abercrombie, Daniel Robert (Author), Allen, Branden (Author), Azzolini, Virginia (Author), Baty, Austin Alan (Author), Bauer, Gerry P (Author), Bi, Ran (Author), Brandt, Stephanie Akemi (Author), Busza, Wit (Author), Cali, Ivan Amos (Author), D'Alfonso, Mariarosaria (Author), Demiragli, Zeynep (Author), Gomez-Ceballos, Guillelmo (Author), Goncharov, Maxim (Author), Harris, Philip Coleman (Author), Hsu, David (Author), Hu, Miao (Author), Iiyama, Yutaro (Author), Innocenti, Gian Michele (Author), Klute, Markus (Author), Kovalskyi, Dmytro (Author), Lee, Y.S (Author), Luckey Jr, P David (Author), Maier, Benedikt (Author), Marini, Andrea Carlo (Author), McGinn, Christopher Francis (Author), Mironov, Camelia Maria (Author), Narayanan, S. (Author), Niu, Xinmei (Author), Paus, Christoph M. E. (Author), Roland, Christof (Author), Roland, Gunther M (Author), Stephans, George S. F. (Author), Sumorok, Konstanty C (Author), Velicanu, Dragos Alexandru (Author), Wang, J. (Author), Wang, T.W (Author), Wyslouch, Boleslaw (Author), Zhaozhong, S. (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor), Massachusetts Institute of Technology. Laboratory for Nuclear Science (Contributor)
• Format: Article
• Language: English
• Published: 2022-08-18T16:27:39Z.
• Subjects: Article
• Online Access: Get fulltext

© 2018 CERN, for the CMS Collaboration. 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).