A wealth of observations, dating back 70 years, show that the universe is composed of >96% invisible matter and energy. The nature of these missing components is one of the most fundamental mysteries in physics, and has attracted broad attention from the public. The leading candidate for the invisible dark matter is a subatomic particle left over from the big bang known as the Weakly Interacting Massive Particle (WIMP). Such particles are also predicted by supersymmetry, a favored class of new particle models. If WIMPs exist, they are also the dominant mass in our own Milky Way. Though they only very rarely interact with conventional matter, they should nonetheless be detectable by sufficiently sensitive detectors on Earth, through their direct interaction with, and the ensuing recoil of, nuclei in a target material. The primary challenge in detecting them is reducing natural and cosmogenic radioactivity by up to 10 orders of magnitude.

The LUX collaboration has assembled a team with the breadth and depth of experience and knowledge to carry out the program outlined in this proposal, and to establish a clear leadership role for the United States in the field of direct dark matter detection. LUX is composed of the majority of the US groups from XENON10, the majority of the US component of ZEPLIN II, and new groups that bring essential experience in background rejection and rare event detection from the large scale neutrino experiments SuperK, SNO, Kamland and Double Chooz. The collaboration will design, construct and deploy a 300 kg active mass two-phase Xe experiment that will extend current dark matter sensitivity two orders of magnitude beyond current best limits, to an event rate better than ~1 event/100 kg/month. A large detector is required to not only set such a sensitivity limit, but also to accumulate WIMP statistics in a reasonable time frame if a signal is detected. The LUX program will also help develop the technologies required for 1-10 ton dark matter detectors.

This video is a simple 3-D simulation of the particle detection mechanism.