Light, long-lived B − L gauge and Higgs bosons at the DUNE near detector

A bstract The low-energy U(1) B−L gauge symmetry is well-motivated as part of beyond Standard Model physics related to neutrino mass generation. We show that a light B − L gauge boson Z′ and the associated U(1) B−L -breaking scalar φ can both be effectively searched for at high-intensity facilities such as the near detector complex of the Deep Underground Neutrino Experiment (DUNE). Without the scalar φ , the Z ′ can be probed at DUNE up to mass of 1 GeV, with the corresponding gauge coupling g BL as low as 10 − 9 . In the presence of the scalar φ with gauge coupling to Z ′, the DUNE capability of discovering the gauge boson Z ′ can be significantly improved, even by one order of magnitude in g BL , due to additional production from the decay φ → Z ′ Z ′. The DUNE sensitivity is largely complementary to other long-lived Z ′ searches at beam-dump facilities such as FASER and SHiP, as well as astrophysical and cosmological probes. On the other hand, the prospects of detecting φ itself at DUNE are to some extent weakened in presence of Z ′, compared to the case without the gauge interaction.