Search for an Lμ - Lτ gauge boson using Z → 4μ events in proton-proton collisions at √s = 13 TeV
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Published version
Author(s)
Type
Journal Article
Abstract
A search for a narrow Z gauge boson with a mass between 5 and 70 GeV resulting from an Lμ − Lτ
U(1) local gauge symmetry is reported. Theories that predict such a particle have been proposed as an
explanation of various experimental discrepancies, including the lack of a dark matter signal in directdetection experiments, tension in the measurement of the anomalous magnetic moment of the muon,
and reports of possible lepton flavor universality violation in B meson decays. A data sample of protonproton collisions at a center-of-mass energy of 13 TeV is used, corresponding to an integrated luminosity
of 77.3 fb−1 recorded in 2016 and 2017 by the CMS detector at the LHC. Events containing four muons
with an invariant mass near the standard model Z boson mass are analyzed, and the selection is further
optimized to be sensitive to the events that may contain Z → Z
μμ → 4μ decays. The event yields are
consistent with the standard model predictions. Upper limits of 10−8–10−7 at 95% confidence level are
set on the product of branching fractions B(Z → Z
μμ)B(Z → μμ), depending on the Z mass, which
excludes a Z boson coupling strength to muons above 0.004–0.3. These are the first dedicated limits on
Lμ − Lτ models at the LHC and result in a significant increase in the excluded model parameter space.
The results of this search may also be used to constrain the coupling strength of any light Z gauge boson
to muons
U(1) local gauge symmetry is reported. Theories that predict such a particle have been proposed as an
explanation of various experimental discrepancies, including the lack of a dark matter signal in directdetection experiments, tension in the measurement of the anomalous magnetic moment of the muon,
and reports of possible lepton flavor universality violation in B meson decays. A data sample of protonproton collisions at a center-of-mass energy of 13 TeV is used, corresponding to an integrated luminosity
of 77.3 fb−1 recorded in 2016 and 2017 by the CMS detector at the LHC. Events containing four muons
with an invariant mass near the standard model Z boson mass are analyzed, and the selection is further
optimized to be sensitive to the events that may contain Z → Z
μμ → 4μ decays. The event yields are
consistent with the standard model predictions. Upper limits of 10−8–10−7 at 95% confidence level are
set on the product of branching fractions B(Z → Z
μμ)B(Z → μμ), depending on the Z mass, which
excludes a Z boson coupling strength to muons above 0.004–0.3. These are the first dedicated limits on
Lμ − Lτ models at the LHC and result in a significant increase in the excluded model parameter space.
The results of this search may also be used to constrain the coupling strength of any light Z gauge boson
to muons
Date Issued
2019-05-10
Date Acceptance
2019-01-08
Citation
Physics Letters B, 2019, 792, pp.345-368
ISSN
0370-2693
Publisher
Elsevier
Start Page
345
End Page
368
Journal / Book Title
Physics Letters B
Volume
792
Copyright Statement
© 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000466802100054&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
Physics, Nuclear
Physics, Particles & Fields
Physics
CMS
Zprime
Muons
Publication Status
Published
OA Location
https://www.sciencedirect.com/science/article/pii/S037026931930214X?via%3Dihub
Date Publish Online
2019-03-28