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Title: Observation of the Z$$\to\psi\ell^+\ell^-$$ decay in pp collisions at $$\sqrt{s}=$$ 13 TeV

Abstract

This Letter presents the observation of the rare Z boson decay Z$$\to\psi\ell^+\ell^-$$. Here, $$\psi$$ represents contributions from direct J/$$\psi$$ and J/$$\psi$$$\to$$ J$$\psi X$$, $$\ell^+\ell^-$$ is a pair of electrons or muons, and the J/$$\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$$(2S) $$\to$$J/$$\psi X$$ contribution, the ratio of the branching fraction of the exclusive decay Z$$\to\psi\ell^+\ell^-$$ to the decay Z$$\to\mu^+\mu^-\mu^+\mu^-$$ within a fiducial phase space is measured to be $$\mathcal{B}($$Z$$\to\psi\ell^+\ell^-) / \mathcal{B}($$Z$$\to\mu^+\mu^-\mu^+\mu^-) =$$ 0.67$$\pm$$ 0.18 (stat) $$\pm$$ 0.05 (syst).

Authors:
;
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Org.:
CMS
OSTI Identifier:
1454705
Report Number(s):
FERMILAB-PUB-18-265-CMS; CMS-BPH-16-001; CERN-EP-2018-131; arXiv:1806.04213
1677496
DOE Contract Number:
AC02-07CH11359
Resource Type:
Journal Article
Resource Relation:
Journal Name: TBD
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Sirunyan, Albert M, and et al. Observation of the Z$\to\psi\ell^+\ell^-$ decay in pp collisions at $\sqrt{s}=$ 13 TeV. United States: N. p., 2018. Web.
Sirunyan, Albert M, & et al. Observation of the Z$\to\psi\ell^+\ell^-$ decay in pp collisions at $\sqrt{s}=$ 13 TeV. United States.
Sirunyan, Albert M, and et al. Mon . "Observation of the Z$\to\psi\ell^+\ell^-$ decay in pp collisions at $\sqrt{s}=$ 13 TeV". United States. doi:. https://www.osti.gov/servlets/purl/1454705.
@article{osti_1454705,
title = {Observation of the Z$\to\psi\ell^+\ell^-$ decay in pp collisions at $\sqrt{s}=$ 13 TeV},
author = {Sirunyan, Albert M and et al.},
abstractNote = {This Letter presents the observation of the rare Z boson decay Z$\to\psi\ell^+\ell^-$. Here, $\psi$ represents contributions from direct J/$\psi$ and J/$\psi$$\to$ J$\psi X$, $\ell^+\ell^-$ 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) $\to$J/$\psi X$ contribution, the ratio of the branching fraction of the exclusive decay Z$\to\psi\ell^+\ell^-$ to the decay Z$\to\mu^+\mu^-\mu^+\mu^-$ within a fiducial phase space is measured to be $\mathcal{B}($Z$\to\psi\ell^+\ell^-) / \mathcal{B}($Z$\to\mu^+\mu^-\mu^+\mu^-) =$ 0.67$\pm$ 0.18 (stat) $\pm$ 0.05 (syst).},
doi = {},
journal = {TBD},
number = ,
volume = ,
place = {United States},
year = {Mon Jun 11 00:00:00 EDT 2018},
month = {Mon Jun 11 00:00:00 EDT 2018}
}