Probing new physics at DUNE operating in a beam-dump mode

In this work we demonstrate that a future accelerator-based neutrino experiment such as DUNE can greatly increase its sensitivity to a variety of new physics scenarios by operating in a mode where the proton beam impinges on a beam dump. We consider two new physics scenarios, namely light dark matter and axionlike particles and show that by utilizing a dump mode at a DUNE-like experiment, unexplored new regions of parameter space can be probed with an exposure of only 3 months with half of its expected initial beam power. Specifically, targetless configuration of future high intensity neutrino experiments will probe the parameter space for thermal relic dark matter as well as the QCD axion. The strength of such a configuration in the context of new physics searches stems from the fact that the neutrino flux is significantly reduced compared to that of the target, resulting in much smaller backgrounds from neutrino interactions. We have verified this in detail by explicitly computing neutrino fluxes which we make publicly available in order to facilitate further studies with a targetless configuration.