ACP Seminar (Astronomy - Cosmology - Particle Physics)

Speaker: Jing Liu (Max Planck Institut fuer Physik, Muenchen, Germany)
Title: Development of segmented germanium detectors for neutrinoless double beta decay experiments
Date (JST): Tue, Mar 24, 2009, 10:30 - 11:30
Place: Seminar Room at IPMU Kamioka Satellite
Related File: 61.pdf
Abstract: What is the absolute mass scale for neutrinos? Are neutrino and anti-neutrino are identical, i.e. Majorana particles? Neutrinoless double beta decay experiments can help to improve our understanding in
both cases and are the most practical method known to tackle the second question. The GERmanium Detector Array (GERDA), searching for neutrinoless double beta decay of $^{76}$Ge, is currently under construction in Hall A of the INFN Gran Sasso National Laboratory (LNGS), Italy. In order to achieve an extremely low background level, segmented germanium detectors will be operated directly in liquid argon which serves as cooling and shielding material simultaneously.

Several test cryostats were built to operate segmented germanium detectors in vacuum and submerged in cryogenic liquid at the Max-Planck-Institut für Physik in München. The performance and the background discrimination power of segmented germanium detectors were studied in detail. It was proved for the first time that segmented germanium detectors can be operated stably over a long period submerged in a cryogenic liquid. It was confirmed that the segmentation scheme employed does well in the identification of photon induced background and demonstrated for the first time that also neutron interactions can be identified. Simulations of low energy photon and neutron interactions were performed and verified to hold to 5%.

Pulse shape analysis is complementary to segmentation in identifying background events. Its efficiency can only be correctly determined using reliable pulse shape simulations. A fully functional pulse shape simulation package was developed. The simulation was verified using data taken with the first segmented prototype detector for GERDA. This work also led to a considerable improvement in the understanding of segmented germanium detectors.
Remarks: to be broadcasted to Tokatsu 405