Leptonic scalar portal: Origin of muon $g-2$ anomaly and dark matter?

Abstract

We present a model explaining both the 4.2 $\sigma$ muon $g-2$ anomaly and the relic density of dark matter (DM) in which DM interacts with the Standard Model (SM) via a scalar portal boson $\phi$ carrying both dark and SM leptonic numbers, and mediating a nondiagonal interaction between the electron and muon that allows $e\leftrightarrow \mu$ transitions. The $\phi$ could be produced in high-energy electron scattering off a target nuclei in the reaction $eZ\to \mu Z\phi$ followed by the prompt invisible decay $\phi \to$~DM particles and searched for in events with large missing energy accompanied by a single outgoing muon in the final state. Interestingly, several events with a similar signature have been observed in a data sample of $\simeq 3\times 10^{11}$ electrons on target collected during 2016-2018 for the search for light dark matter in the NA64 experiment at the CERN SPS [PRL {\bf 123}, 121801 (2019)]. Attributing so far these events to background allows us to set first constraints on the $\phi$ mass and couplings while leaving at the same time decisively probing the origin of these events and a large fraction of the remaining parameter space to a near exiting future with the upgraded NA64 detector or other planned experiments.

6 pages, 3 figures. References added, matches published version

References in corpus (16)

• Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm
• The anomalous magnetic moment of the muon in the Standard Model
• The $g-2$ of charged leptons, $\alpha (M_Z^2)$ and the hyperfine splitting of muonium
• Hadronic contribution to the muon anomalous magnetic moment to next-to-next-to-leading order
• New physics explanations of $a_{\mu }$ in light of the FNAL muon $g-2$ measurement
• Search for invisible decays of sub-GeV dark photons in missing-energy events at the CERN SPS
• Muon g-2 and searches for a new leptophobic sub-GeV dark boson in a missing-energy experiment at CERN
• Search for the lepton flavor violating decay $Z\to e\mu$ in pp collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector
• Systematically Testing Singlet Models for $(g-2{)}_{\mu }$
• Constraints on New Physics in the Electron g-2 from a Search for Invisible Decays of a Scalar, Pseudoscalar, Vector, and Axial Vector
• Prospects in the search for a new light $Z^{\prime }$ boson with the NA64$\mu$ experiment at the CERN SPS
• Fully Geant4 compatible package for the simulation of Dark Matter in fixed target experiments
• Implication of the hidden sub-GeV bosons for the $(g-2{)}_{\mu }$, ${}^8$Be-${}^4$He anomaly, proton charge radius, EDM of fermions and dark axion portal
• The Simplest and Most Predictive Model of Muon $g-2$ and Thermal Dark Matter
• Search for dark sector physics with NA64
• Probing Hidden Sectors with a muon beam: Total and differential cross-sections for vector boson production in muon bremsstrahlung

Cited by in corpus (4)

• Implication of the dark axion portal for the EDM of fermions and dark matter probing with NA64$e$, NA64$\mu$, LDMX, $\mbox{M}^3$, and BaBar
• Sensitivity potential to a light flavor-changing scalar boson with DUNE and NA64$\mu$
• The Muon Magnetic Moment and Physics Beyond the Standard Model
• Probing charged lepton flavor violation in an economical muon on-target experiment