Data from the DRIFT-IIa directional dark matter experiment are presented, collected during a near continuous 6 month running period. A detailed calibration analysis comparing data from gamma-ray, x-ray and neutron sources to a GEANT4 Monte Carlo simulations reveals an efficiency for detection of neutron induced recoils of 94+/-2(stat.)+/-5(sys.)%. Software-based cuts, designed to remove non-nuclear recoil events, are shown to reject 60Co gamma-rays with a rejection factor of better than 8x10-6 for all energies above threshold. An unexpected event population has been discovered and is shown here to be due to the alpha-decay of 222Rn daughter nuclei that have attached to the central cathode. A limit on the flux of neutrons in the Boulby Underground Laboratory is derived from analysis of unshielded and shielded data.
@article{arxiv.0707.1488,
title = {First Results from the DRIFT-IIa Dark Matter Detector},
author = {S. Burgos and J. Forbes and C. Ghag and M. Gold and V. A. Kudryavtsev and T. B. Lawson and D. Loomba and P. Majewski and D. Muna and A. StJ. Murphy and G. G. Nicklin and S. M. Paling and A. Petkov and S. J. S. Plank and M. Robinson and N. Sanghi and N. J. T. Smith and D. P. Snowden-Ifft and N. J. C. Spooner and T. J. Sumner and J. Turk and E. Tziaferi},
journal= {arXiv preprint arXiv:0707.1488},
year = {2008}
}
Comments
43 pages, 14 figures, submitted to Astroparticle Physics