A dark leptophilic scalar with the updated muon $$g-2$$ anomaly

Abstract

AbstractThe muon $$g-2$$ g - 2 anomaly was strengthened by recent experimental results at Fermilab, which may be signatures of new physics. A scenario of leptophilic scalar $$\phi _L$$ ϕ L accounting for the muon $$g-2$$ g - 2 anomaly is investigated in this paper. Although a light $$\phi _L$$ ϕ L mainly decaying into standard model (SM) particles has been excluded by experiments, a dark leptophilic scalar $$\phi _L$$ ϕ L predominantly decaying into invisible fermionic dark matter (DM) $$\chi {\bar{\chi }}$$ χ χ ¯ is still allowed. Considering the decay mode $$\phi _L \rightarrow \chi {\bar{\chi }}$$ ϕ L → χ χ ¯ opened (here $$m_{\phi _L} = 3 m_\chi $$ m ϕ L = 3 m χ ), the coupling preferred by the muon $$g-2$$ g - 2 and the $$\phi _L-\chi $$ ϕ L - χ coupling are derived. The light/heavy $$\phi _L$$ ϕ L (roughly 1 GeV as a benchmark value) can be tested by future experiments via DM/SM decay modes, and the contribution of $$\phi _L$$ ϕ L to the anomalous magnetic moment of the tau lepton could be investigated at lepton colliders. The search for $$\chi $$ χ via $$\chi $$ χ -electron scattering in direct detection of DM is not sensitive due to a tiny $$\phi _L$$ ϕ L -electron coupling, especially for $$m_\chi > rsim m_\mu $$ m χ ≳ m μ .