Backgrounds at all energies were reduced moving from Cuoricino (black line) to CUORE-0 (red shaded region). In CUORE-0, the background index in the region 2700–3900 keV, excluding the 190Pt peak at 3290 keV, is 0.016 ± 0.001 counts/(keV⋅kg⋅yr), a factor of 6.8 reduction compared to Cuoricino. The background in the region of interested was reduced to 0.058 ± 0.004 counts/(keV⋅kg⋅yr), a factor of 2.7 over Cuoricino. This is consistent with our models that place the origin of the γ contamination in the cryostat materials, which are common to both CUORE-0 and Cuoricino. This γ background forms an irreducible background for CUORE-0, but is expected to be significantly reduced in CUORE due to better material selection, better shielding, and more efficient anti-coincidence rejection.
image: K. Alfonso et al. (CUORE Collaboration). Phys. Rev. Lett. 115, 102502 (2015)