Experimental Search for Solar Axions via Coherent Primakoff Conversion in a Germanium Spectrometer

Abstract

Results are reported of an experimental search for the unique, rapidly varying temporal pattern of solar axions coherently converting into photons via the Primakoff effect in a single crystal germanium detector. This conversion is predicted when axions are incident at a Bragg angle with a crystalline plane. The analysis of approximately 1.94 kg.yr of data from the 1 kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound on axion-photon coupling of $g_{aγγ} < 2.7\cdot 10^{-9}$ GeV$^{-1}$, independent of axion mass up to ~ 1 keV.

Figures (5)

• Figure 1: Feynman diagram of the Primakoff conversion of axions into photons.
• Figure 2: A typical axion--photon conversion rate, $R(t,E)$, for various energy bands. The experimental energy resolution FWHM = 1.0 keV at 10 keV was used.
• Figure 3: Scatter plot showing the distribution on the celestial sphere of all events between 4 keV and 8 keV over the data collection period of 707 days.
• Figure 4: Values of $\lambda$ calculated from the 707 days of data as a function of the azimuthal angle $\phi$. The error bars are $1 \sigma$.
• Figure 5: Exclusion plots on the $g_{a \gamma \gamma}$ vs. axion--mass plane. The curve to the left are from Ref. [16]. The letters indicate the following helium gas pressures in the conversion region of a strong magnetic field: (a) vacuum, (b) 55 Torr, and (c) 100 Torr.