Light, Long-Lived $B-L$ Gauge and Higgs Bosons at the DUNE Near Detector

TL;DR

This paper explores how the DUNE near detector can effectively search for light, long-lived $B-L$ gauge bosons and scalars, providing new sensitivity to these particles beyond existing experiments and astrophysical constraints.

Contribution

It demonstrates the potential of DUNE to detect light $B-L$ gauge bosons and scalars, especially considering the scalar's role in enhancing $Z'$ production, which is a novel approach.

Findings

DUNE can probe $Z'$ masses up to 1 GeV with couplings as low as 10^{-9}.

Scalar $$ can significantly boost $Z'$ discovery prospects via decay channels.

DUNE's sensitivity is complementary to other long-lived particle searches and astrophysical probes.

Abstract

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 $\varphi$ 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 $\varphi$, 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 $\varphi$ 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 $\varphi \to Z{'}Z{'}$. 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 $\varphi$ itself at DUNE are to some extent weakened in presence of $Z{'}$, compared to the case without the gauge interaction.