Search for an Invisibly Decaying Z^ ' Boson at Belle II in e^ + e^ - →μ^ + μ^ - (e^ ± μ^ ∓ ) Plus Missing Energy Final States.
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| Abstract | :
Theories beyond the standard model often predict the existence of an additional neutral boson, the Z^{'}. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a Z^{'} in the process e^{+}e^{-}→μ^{+}μ^{-}Z^{'} and of a lepton-flavor-violating Z^{'} in e^{+}e^{-}→e^{±}μ^{∓}Z^{'}. We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an L_{μ}-L_{τ} theory, into upper limits on the Z^{'} coupling constant at the level of 5×10^{-2}-1 for M_{Z^{'}}≤6 GeV/c^{2}. |
| Year of Publication | :
2020
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| Journal | :
Physical review letters
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| Volume | :
124
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| Issue | :
14
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| Number of Pages | :
141801
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| Date Published | :
2020
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| ISSN Number | :
0031-9007
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| URL | :
https://link.aps.org/abstract/PRL/v124/p141801
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| DOI | :
10.1103/PhysRevLett.124.141801
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| Short Title | :
Phys Rev Lett
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