The potential of hybrid pixel detectors in the search for the neutrinoless double-beta decay of 116Cd

Abstract

We investigated the potential of the energy resolving hybrid pixel detector Timepix contacted to a CdTe sensor layer for the search for the neutrinoless double-beta decay of C d. We found that a CdTe sensor layer with 3 mm thickness and 165 m pixel pitch is optimal with respect to the effective Majorana neutrino mass (m β β) sensitivity. In simulations, we were able to demonstrate a possible reduction of the background level caused by single electrons by approximately 75% at a specific background rate of 10-3 counts/(k g × k e V × y r) at a detection efficiency reduction of about 23% with track analysis employing random decision forests. Exploitation of the imaging properties with track analysis leads to an improvement in sensitivity to m β β by about 22%. After 5 years of measuring time, the sensitivity to m β β of a 420 kg CdTe experiment (90% C d enrichment) would be 59 meV on a 90% confidence level for a specific single-electron background rate of 10-3 counts/(k g × k e V × y r). The α-particle background can be suppressed by at least about six orders of magnitude. The benefit of the hybrid pixel detector technology might be increased significantly if drift-time difference measurements would allow reconstruction of tracks in three dimensions. © 2013 Thilo Michel et al.