Abstract
Data from the operation of a bubble chamber filled with 3.5 kg of in a shallow underground site are reported. An analysis of ultrasound signals accompanying bubble nucleations confirms that alpha decays generate a significantly louder acoustic emission than single nuclear recoils, leading to an efficient background discrimination. Three dark matter candidate events were observed during an effective exposure of , consistent with a neutron background. This observation provides strong direct detection constraints on weakly interacting massive particle (WIMP)-proton spin-dependent scattering for WIMP masses .
- Received 20 August 2010
DOI:https://doi.org/10.1103/PhysRevLett.106.021303
© 2011 The American Physical Society