Statistical techniques developed by the UKDMC to calculate the 90% c.l. upper limit of the WIMP component of the Galactic dark matter

Abstract

This paper outlines statistical techniques developed by the UK Dark Matter Collaboration to convert the resultant energy spectra from NaI crystal scintillation detectors to a 90% confidence level upper limit to the rate of the hypothetical weakly interacting massive dark matter particle, the WIMP. In simple counting systems a chi-square surface minimisation technique is used, the 90% c.l. arising from Monte Carlo simulations. In detectors that exhibit electron from nuclear recoil discrimination a comparison between the observed spectrum and that from gamma and neutron calibrations is performed with chi-square, Kolmogorov-Smirnov and Cramer-von-Mises tests to give the most likely signal, with Monte Carlo simulations again yielding the 90% c.l.