Homestake Ultra-Low Background Counting Facility and Detection of Double-Beta Decay to Excited States

A powerful, ultra-low background counting facility, for material screening is crucial to the success of many deep underground science and engineering laboratory (DUSEL) experiments dealing with extremely rare-occurring processes that are of great scientific importance. In order to reach the ultimate sensitivity necessary for these experiments such as (e.g.) in dark matter searches and nuclear double beta-decay, only materials with the lowest possible radioactivity can be used in fabricating the experimental devices, and the entire setup must be located in a deep underground site. The Homestake Mine, home to the first solar neutrino experiment, provides an excellent opportunity to host DUSEL, as well as the required ultra-low background laboratory facility. Besides low background counting, detectors in this facility can also be used to perform important physics experiments, such as studying the nuclear double-beta decay to excited-state process, a topic which has recently drawn both strong experimental and theoretical interests. Experimentally, it is a great advantage to be able to detect unambiguously the gamma-rays from the de- excitation of the daughter nucleus to its ground state, as proposed in our method.