Probing sub-GeV mass SIMP dark matter with a low-threshold surface experiment

Using data from the $\nu$-cleus detector, based on the surface of the Earth, we place constraints on dark matter in the form of Strongly Interacting Massive Particles (SIMPs) which interact with nucleons via nuclear-scale cross sections. For large SIMP-nucleon cross sections the sensitivity of traditional direct dark matter searches using underground experiments is limited by the energy loss experienced by SIMPs, due to scattering with the rock overburden and experimental shielding on their way to the detector apparatus. Hence a surface-based experiment is ideal for a SIMP search, despite the much larger background, resulting from the lack of shielding. We show using data from a recent surface run of a low-threshold cryogenic detector that values of the SIMP-nucleon cross section up to approximately $10^{-27}$ cm$^2$ can be excluded for SIMPs with masses above 100 MeV.