Probing general U(1)' models with non-universal lepton charges at FASER/FASER2, COHERENT and long-baseline oscillation experiments

The general anomaly-free U(1)' models allow non-universal lepton charges. We explore the sensitivities of FASER/FASER2, COHERENT and DUNE/T2HK precision experiments to the new gauge boson Z' and the new CP-even scalar phi. With non-universal lepton charges, distinctive reaches at FASER/FASER2 emerge in the regime of low mZ' and small gauge coupling gBL for different U(1)' charge setups. The COHERENT experiment and the future long-baseline experiments DUNE/T2HK also provide complementary probes to the available parameter space. For m(phi) < 2m(Z'), the search for the scalar phi at FASER/FASER2 is sensitive to the mixing angle between the scalar singlet and the SM Higgs. In the case of m(phi) > 2m(Z)', the kinematically allowed decay phi -> Z'Z' changes the lifetime and decay rates of the scalar.. The sensitivity reach highly depends on the Z' mass and the gauge coupling g(BL)

Automated summary

This study explores the sensitivities of precision experiments to the U(1) models with non-universal lepton charges, and proposes detection methods for the new gauge boson Z' and the new CP-even scalar phi with FASER/FASER2, COHERENT, and DUNE/T2HK experiments.