München 2009 – scientific programme
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T: Fachverband Teilchenphysik
T 101: Niederenergie-Neutrinophysik & Suche nach dunkler Materie 2
T 101.2: Talk
Tuesday, March 10, 2009, 17:05–17:20, A140
Search for Axions with the CDMS-II Experiment — •Tobias Bruch — Physik-Institut, Universität Zürich, Schweiz
Originally designed for the search for Weakly Interacting Massive Particles (WIMPs), the CDMS-II experiment is also able to search for solar and relic axions. The low electron recoil background level of ∼1.5 dru and the low threshold of 2 keV for electron recoils allows to search for a signature in the electromagnetic interactions, which are rejected in the WIMP search analysis. Solar axions may be detected by the Primakov conversion to photons. The Bragg condition for X-ray momentum transfer in a crystal allows for coherent amplification of the Primakov process. Since the orientation of the crystal lattice with respect to the sun changes with daytime an unique pattern in time and energy of solar axion conversions is expected. The analysis of 443.2 kg-days of germanium exposure sets an upper limit on the axion photon coupling constant of gaγγ < 2.4 × 10−9 GeV−1 at a 95% CL.
Conversions of relic axions distributed in the local halo in the detectors via the axio-electric effect would result in a line at an energy equivalent to the axion mass. The analysis of the low energy spectra resulted in no statistically significant excess in the detected rate above background. This analysis sets an upper limit on the axio-electric coupling of gaēe < 1.4 × 10−12 at the 90% CL for an axion mass of 2.5 keV, excluding the DAMA allowed region and sets the best laboratory upper bound for masses above 1.4 keV. The upper limits on an excess rate provide a general constraint on the electromagnetic interpretation of the annual modulation signature observed by DAMA.