New data are reported from the operation of a 2-liter C3F8 bubble chamber in the 2100 meter deep SNOLAB underground laboratory, with a total exposure of 211.5 kg-days at four different recoil energy thresholds ranging from 3.2 keV to 8.1 keV. These data show that C3F8 provides excellent electron recoil and alpha rejection capabilities at very low thresholds, including the rst observation of a dependence of acoustic signal on alpha energy. Twelve single nuclear recoil event candidates were observed during the run. The candidate events exhibit timing characteristics that are not consistent with the hypothesis of a uniform time distribution, and no evidence for a dark matter signal is claimed. These data provide the most sensitive direct detection constraints on WIMP-proton spin-dependent scattering to date, with signicant sensitivity at low WIMP masses for spin-independent WIMP-nucleon scattering.
Revised: January 19, 2016 |
Published: June 12, 2015
Citation
Amole C., M. Ardid, D.M. Asner, D. Baxter, E. Behnke, P.S. Bhattacharjee, and H. Borsodi, et al. 2015.Dark Matter Search Results from the PICO-2L C3F8 Bubble Chamber.Physical Review Letters 114, no. 23:Article No. 231302.PNNL-SA-108605.doi:10.1103/PhysRevLett.114.231302