Searching for Dark Matter with a Bubble Chamber
Peter S. Cooper
From astrophysical observations we know that 85% of the matter in galaxies is DARK, interacting only gravitationally with normal matter but completely dominating the motion of stars in a galaxy. I will describe a direct search for Dark Matter in the lab using a bubble chamber as a nuclear recoil detector to look for both spin-dependent and spin-independent WIMP-nucleus scattering events. [Weakly Interacting Massive Particles (WIMPs) are the M-100 GeV/c^2 particle physics hypothesis for Dark Matter. The Lightest Supersymmetric Particle is the most obvious candidate.] The COUPP collabopration has built and operated a series of heavy liquid room temperature bubble chambers, of increasing size and sensitivity. This work has yielded the best limits in the world on spin-dependent WIMP-nucleus scattering cross sections. Data being taken now should permit us to become competitive with the best in the world spin-independent measurements. This work is done with 2-4 kg chambers. A 60 kg chamber is being debugged. I will discuss the Dark Matter problem and current direct detection searchs with an emphasis on our recent work as well as prpospects for the near future.