Search for solar axions by Primakoff effect in NaI crystals

The results of a search for possible signal due to Primakoff coherent conversion of solar axions into photons in NaI(Tl) are presented. The experiment has been carried out at the Gran Sasso National Laboratory of INFN; the used statistics is 53 437 kg day. The presently most stringent experimental limit on gaγγ from this process is obtained: gaγγ<1.7×10−9 GeV−1 (90% C.L.). In particular, the axion mass window ma≳0.03 eV, not accessible by other direct methods, is explored and KSVZ axions with mass larger than 4.6 eV are excluded at 90% C.L.