Direct dark matter search by annual modulation in XMASS-I

A search for dark matter was conducted with the XMASS detector by means of the expected annual modulation due to the Earth's rotation around the Sun. The data used for this analysis was 359.2 live days \(\times\) 832 kg of exposure accumulated between November 2013 and March 2015. The result of a simple modulation analysis, without assuming any specific dark matter model, showed a slight negative amplitude. As the \(p\)-values are 6.1 or 17\% in our two independent analyses, these results are consistent with fluctuations. We also set 90\% confidence level (C.L.) upper bounds that can be used to test models. When we assume Weakly Interacting Massive Particle (WIMP) dark matter elastically scattering on the target nuclei, we exclude almost all the DAMA/LIBRA allowed region with the modulation analysis. This is the first extensive search probing this region with redan exposure comparable to theirs.