Search for solar axion emission from⁷Li and D(p, γ)³He nuclear decays with the CAST γ-ray calorimeter

We present the results of a search for a high-energy axion emission signal from Li-7 (0.478 MeV) and D(p,gamma)He-3 (5.5 MeV) nuclear transitions using a low-background gamma-ray calorimeter during Phase I of the CAST experiment. These so-called "hadronic axions" could provide a solution to the long-standing strong-GP problem and can be emitted from the solar core from nuclear M1 transitions. This is the first such search for high-energy pseudoscalar bosons with couplings to nucleons conducted using a helioscope approach. No excess signal above background was found.