About XMASS Preface

Dear Visitors,

Welcome to XMASS Home Page. XMASS is the experiment aiming to detect dark matter directly. Dark matter is thought to constitute about 80% of the matter of the Universe, and thought to be an essential ingredient to form stars and galaxies in the course of the development of the universe and therefore human beings or even life never exist in the universe without dark matter. However, it is mysterious enough nobody knows what dark matter is.

XMASS is originally conceived as a versatile detector using liquid xenon to measure low energy solar neutrinos, and to look for neutrino-less double beta decay and dark matter. As a first step towards the ultimate goal, we have constructed a small scale detector using about 800 kg of liquid xenon as an initial step dedicated to search for the dark matter interactions in the detector.

To unveil the secret of dark matter is one of the most important issues in the universe and therefore there are many experiments in the world to try to find dark matter. So far no experiments gave convincing evidence for detection of dark matter directly. Furthermore we also do not have any indication of the production of dark matter at the high energy accelerator experiments like at LHC. It is pointed out that it is very important to look for much wider category of dark matter in addition to the WIMP dark matter that has been well-motivated candidates for the past years.

XMASS is incidentally suited for a search for different kinds of dark matter other than WIMPs. We have reduced the background found in our commissioning run and we have started to take data in November 2013.

Yoichiro Suzuki
Spokesperson, the XMASS collaboration
December-28, 2015.