First dark matter search results from a 4-kg CF 3I bubble chamber operated in a deep underground site

E. Behnke*, J. Behnke, S. J. Brice, D. Broemmelsiek, J. I. Collar, A. Conner, P. S. Cooper, M. Crisler, C. E. Dahl, D. Fustin, E. Grace, J. Hall, M. Hu, I. Levine, W. H. Lippincott, T. Moan, T. Nania, E. Ramberg, A. E. Robinson, A. SonnenscheinM. Szydagis, E. Vázquez-Jáuregui

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

247 Scopus citations


New data are reported from the operation of a 4.0-kg CF 3I bubble chamber in the 6800-foot-deep SNOLAB underground laboratory. The effectiveness of ultrasound analysis in discriminating alpha-decay background events from single nuclear recoils has been confirmed, with a lower bound of >99.3% rejection of alpha-decay events. Twenty single nuclear recoil event candidates and three multiple bubble events were observed during a total exposure of 553 kg-days distributed over three different bubble nucleation thresholds. The effective exposure for single bubble recoil-like events was 437.4 kg-days. A neutron background internal to the apparatus, of known origin, is estimated to account for five single nuclear recoil events and is consistent with the observed rate of multiple bubble events. The remaining excess of single bubble events exhibits characteristics indicating the presence of an additional background. These data provide new direct detection constraints on WIMP-proton spin-dependent scattering for WIMP masses >20GeV/c2 and demonstrate significant sensitivity for spin-independent interactions.

Original languageEnglish (US)
Article number052001
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number5
StatePublished - Sep 5 2012

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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