Search for Light Dark Matter with NEWS-G at the Laboratoire Souterrain de Modane Using a Methane Target

The NEWS-G direct detection experiment uses spherical proportional counters to search for light dark matter candidates. New results from a 10 day physics run with a $135\mathrm{c}\mathrm{m}$ in diameter spherical proportional counter at the Laboratoire Souterrain de Modane are reported. The target consists of $114\mathrm{g}$ of methane, providing sensitivity to dark matter spin-dependent coupling to protons. New constraints are presented in the mass range $0.17$ to $1.2\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{/}{\mathrm{c}}^2$, with a 90% confidence level cross-section upper limit of $30.9\mathrm{p}\mathrm{b}$ for a mass of $0.76\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{/}{\mathrm{c}}^2$.