Prospects of solar axion searches with crystal detectors

A calculation of the expected signal due to Primakoff coherent conversion o f solar axions into photons via Bragg scattering in several crystal detecto rs is presented. The results are confronted with the experimental sensitivi ties of present and future experiments concluding that the sensitivity of c rystal detectors does not challenge the globular cluster limit on the axion -photon coupling g(alpha gamma gamma). In particular, in the axion mass win dow m(alpha) greater than or similar to 0.03 eV explored with this techniqu e (not accessible at present by other methods), g(alpha gamma gamma) might be constrained down to 10(-9) GeV-1 (the recent helioseismological bound) p rovided that significant improvements in the parameters and performances of these detectors be achieved and large statistics accumulated. This bound s hould be considered as a minimal goal for the sensitivity of future crystal experiments. Consequently, finding a positive signal at this level of sens itivity would necessarily imply revisiting other more stringent astrophysic al limits derived for the same range of m(a) values. (C) 1999 Elsevier Scie nce B.V.