The light leptophilic gauge boson Zx and the leptonic decays of charged pseudoscalar mesons

Abstract

The light leptophilic gauge boson Zx predicted by the U(1)Lx models can contribute to the lepton flavor universality (LFU) parameter Rℓ/ℓ′P and the leptonic decays P→ℓνℓℓ′ℓ′¯ via the process P→ℓνℓZx with Zx decaying into a pair of neutrinos or charged leptons, where P denotes the charged pseudoscalar mesons π±, K±, D(s)± or B±. Using the corresponding experimental data, we obtain the constraints on different U(1)Lx models. The most strict constraints on the U(1)Lx models come from the decay K+→μ+νμe+e−.