Constraining U(1) L μ – L τ charged dark matter model for muon g – 2 anomaly with AMS-02 electron and positron data

Abstract

Very recently, the Fermi-Lab reported the new experimental combined results on the magnetic momentum of muon with a 4.2σ discrepancy compared with the expectation of the Standard Model [1]. A new light gauge boson X in the Lμ – Lτ model provides a good explanation for the g – 2 anomaly. A Dirac fermion dark matter with a large Lμ – Lτ charge can explain both the g – 2 anomaly and the dark matter relic density [2]. In this work, we focus on the case that the mass of the dark matter is larger than the mass of muon (i.e. m Ψ > m μ) for which the channel ΨΨ ⟶ μ - μ + opens. Although the cross section (σ v) μ - μ + is smaller by a factor of 1/q Ψ 2 (q Ψ represents the Lμ – Lτ charge of the dark matter) compared with the channel ΨΨ ⟶ X X ⟶ ννν̅ν̅, the resulting secondary electrons and positrons could imprint on their spectra above GeV energies due to the reacceleration effect of cosmic ray propagation. We use the AMS-02 measurements of electrons and positrons to constrain the annihilation cross section of the channel ΨΨ ⟶ μ - μ +, which rules out part of the parameter space of the large Lμ – Lτ charged dark matter model to account for the muon g – 2 anomaly.