Search for solar axions emitted in the M1-transition of 7Li* with Borexino CTF

Abstract

Results of background measurements with a prototype of the Borexino detector were used to search for 478∈keV solar axions emitted in the M1-transitions of 7Li*. The Compton conversion of axion to a photon A+e→e+γ, axioelectric effect A+e+Z→e+Z, decay of axion in two photons A→2γ and Primakoff conversion on nuclei A+Z→γ+Z are considered. The upper limit on constants of interaction of axion with electrons, photons and nucleons - gAegAN (1.0-2.4)×10-10 at mA 450∈keV and g AγgAN 5×10-9∈GeV-1 at mA 10∈keV are obtained (90%c.l.). For heavy axions with mass at 100 <10-9-10 -8 are obtained in assumption that gAN depends on m A as for KSVZ axion model. These limits are stronger than obtained in previous laboratory-based experiments using nuclear reactor and artificial radioactive sources. © 2008 Springer-Verlag / Società Italiana di Fisica.