First results from the AMoRE-Pilot neutrinoless double beta decay experiment

Abstract

The advanced molybdenum-based rare process experiment (AMoRE) aims to search for neutrinoless double beta decay (0 nu beta beta) of Mo-100 with similar to 100 kg of Mo-100-enriched molybdenum embedded in cryogenic detectors with a dual heat and light readout. At the current, pilot stage of the AMoRE project we employ six calcium molybdate crystals with a total mass of 1.9 kg, produced from Ca-48-depleted calcium and Mo-100-enriched molybdenum (Ca-48depl (MoO4)-Mo-100). The simultaneous detection of heat(phonon) and scintillation(photon) signals is realized with high resolution metallic magnetic calorimeter sensors that operate at milli-Kelvin temperatures. This stage of the project is carried out in the Yangyang underground laboratory at a depth of 700 m. We report first results from the AMoRE-Pilot 0 nu beta beta search with a 111 kg day live exposure of Ca-48depl (MoO4)-Mo-100 crystals. No evidence for 0 nu beta beta decay of Mo-100 is found, and a upper limit is set for the half-life of 0 nu beta beta of Mo-100 of T-1/2(0 nu) > 9.5 X 10(22) years at 90% C.L. This limit corresponds to an effective Majorana neutrino mass limit in the range < m beta beta > <= (1.2-2.1) eV