Light Dark Matter Search in XENON1T

Liquid xenon detectors are leading the direct search for dark matter (DM) at masses above $5~\mathrm{GeV}$ thanks to excellent background discrimination power, using scintillation and ionization signals. However, requiring a scintillation signal results in a relatively high energy threshold, which limits the sensitivity to low-energy recoils from light DM. In this talk, we report results from a search for light DM signals using only the ionisation signal in the XENON1T detector. Strong event selections were developed to mitigate instrumental backgrounds, reaching $\sim20~\mathrm{events}/ (\mathrm{tonne}\cdot\mathrm{day}\cdot\mathrm{keVee}$) at $0.2~\mathrm{keVee}$. The selected data improves on current limits for DM-nucleus scattering at DM masses within $3-6~\mathrm{GeV}$. When electronic recoils induced by the Migdal effect are considered, constraints can be extended to DM masses as low as $85~\mathrm{MeV}$.