Improved WIMP-search reach of the CDMS II germanium data

TL;DR

This paper reports an improved analysis of CDMS II germanium data, enhancing WIMP detection sensitivity and setting more stringent limits on WIMP-nucleon cross-sections, especially near 8 GeV/c^2 mass.

Contribution

The study introduces new data processing and background rejection techniques, extending the analysis threshold to improve sensitivity to low-mass WIMPs and significantly tightening existing limits.

Findings

Zero candidate events above 10 keV energy threshold.

Set new upper limits on WIMP-nucleon cross-section, improving previous results.

Enhanced analysis methods increased sensitivity by a factor of 2.4 to 2.7.

Abstract

CDMS II data from the 5-tower runs at the Soudan Underground Laboratory were reprocessed with an improved charge-pulse fitting algorithm. Two new analysis techniques to reject surface-event backgrounds were applied to the 612 kg days germanium-detector WIMP-search exposure. An extended analysis was also completed by decreasing the 10 keV analysis threshold to $\sim$5 keV, to increase sensitivity near a WIMP mass of 8 GeV/$c^2$. After unblinding, there were zero candidate events above a deposited energy of 10 keV and 6 events in the lower-threshold analysis. This yielded minimum WIMP-nucleon spin-independent scattering cross-section limits of $1.8 \times 10^{-44}$ and $1.18 \times 10 ^{-41}$ cm$^2$ at 90\% confidence for 60 and 8.6 GeV/$c^2$ WIMPs, respectively. This improves the previous CDMS II result by a factor of 2.4 (2.7) for 60 (8.6) GeV/$c^2$ WIMPs.