Search for an invisible $Z^{\prime }$ in a final state with two muons and missing energy at Belle II

Abstract

The $L_{\mu }-L_{\tau }$ extension of the standard model predicts the existence of a lepton-flavor-universality-violating $Z^{\prime }$ boson that couples only to the heavier lepton families. We search for such a $Z^{\prime }$ through its invisible decay in the process $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}{Z}^{\prime }$. We use a sample of electron-positron collisions at a center-of-mass energy of 10.58GeV collected by the Belle II experiment in 2019-2020, corresponding to an integrated luminosity of 79.7fb${}^{-1}$. We find no excess over the expected standard-model background. We set 90$\%$-confidence-level upper limits on the cross section for this process as well as on the coupling of the model, which ranges from $3\times 10^{-3}$ at low $Z^{\prime }$ masses to 1 at $Z^{\prime }$ masses of 8$GeV/c^2$.

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Cited by in corpus (6)

• Search for a ${\mu }^{+}{\mu }^{-}$ resonance in four-muon final states at Belle II
• Search for a ${\tau }^{+}{\tau }^{-}$ resonance in $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}{\tau }^{+}{\tau }^{-}$ events with the Belle II experiment
• Impact of new particles on the ratio of Electromagnetic form factors
• Letter of Intent: The Forward Physics Facility
• Constraining the heavy leptophilic neutral gauge bosons through the $Z\to {\ell }^{+}{\ell }^{-}$, $W^{\pm }\to {\ell }^{\pm }{\nu }_{\ell }$, and $h\to {\ell }^{+}{\ell }^{-}$ decays
• Invisible decays of vector Charmonia and Bottomonia to determine the Weak Mixing Angle at quarkonia scale