COSME-2 - Results
Low energy spectrum obtained with 311 days (73 kg d) of exposure.
Exclusion plot (in the parametric space: WIMP-nucleon cross section versus WIMP mass) for spin independent interactions at 95% C.L. derived from Mt=73 kg.day of analyzed data (dasehd line). Exclusion plots obtained by COSME (solid line), IGEX_DM (dot-dashed line) and the 3s-allowed region of the DAMA annual modulation experiment (thin solid line) are also shown.
The main objective of the experiment is the axion detection through its photon Primakoff conversion inside the crystal electric field and its Bragg coherent scattering. In the case of solar axions, a strong correlation between the counting rate and the position of the Sun in the sky is expected. The figure shows a typical example of the temporal pattern expected along one day. This pattern can be used as a distinctive signature of an axion signal or, at the least, to improve the signal-background ratio and to obtain a better exclusion.
A 95% C.L. limit for the axion-photon coupling has been obtained:
gagg < 2.8 x 10-9 GeV-1
This limit is shown in the plot compared with other constraints in the axion parametric space (axion mass versus axion-photon coupling).