DUSEL Theory White Paper

The scientific case for a Deep Underground Science and Engineering Laboratory [DUSEL] located at the Homestake mine in Lead, South Dakota is exceptional. The site of this future laboratory already claims a discovery for the detection of solar neutrinos, leading to a Nobel Prize for Ray Davis. Moreover this work provided the first step to our present understanding of solar neutrino oscillations and a chink in the armor of the Standard Model of particle physics. We now know, from several experiments located in deep underground experimental laboratories around the world, that neutrinos have mass and even more importantly this mass appears to fit into the framework of theories which unify all the known forces of nature, i.e. the strong, weak, electromagnetic and gravitational. Similarly, DUSEL can forge forward in the discovery of new realms of nature, housing six fundamental experiments that will test the frontiers of our knowledge: (1) Searching for nucleon decay (the decay of protons and neutrons predicted by grand unified theories of nature); (2) Searching for neutrino oscillations and CP violation by detecting neutrinos produced at a neutrino source (possibly located at Brookhaven National Laboratory and/or Fermi National Laboratory); (3) Searching for astrophysical neutrinos originating from the sun, from cosmic rays hitting the upper atmosphere or from other astrophysical sources, such a supernovae; (4) Searching for dark matter particles (the type of matter which does not interact electromagnetically, yet provides 24% of the mass of the Universe); (5) Looking for the rare process known as neutrino-less double beta decay which is predicted by most theories of neutrino mass and allows two neutrons in a nucleus to spontaneously change into two protons and two electrons; and (6) Searching for the rare process of neutron- anti-neutron oscillations, which would establish violation of baryon number symmetry. A large megaton water Cherenkov detector for neutrinos and nucleon decay, located in DUSEL and roughly 20 times the size of current detectors, can perform the first three of these experiments. The last 3 can utilize the unique environment afforded by DUSEL to perform the most sensitive tests to date. Any one of these experiments can greatly increase our knowledge of nature. The Deep Underground Science and Engineering Laboratory (DUSEL), with a Large Megaton Size Detector, is desperately needed to address a set of fundamental issues in particle and astrophysics