Search for 14.4 keV solar axions from M1 transition of⁵⁷Fe with CUORE crystals

We report the results of a search for axions from the 14.4 keV M1 transition from 57 Fe in the core of the sun using the axio-electric effect in TeO 2 bolometers. The detectors are 5 × 5 × 5 cm 3 crystals operated at about 10 mK in a facility used to test bolometers for the CUORE experiment at the Laboratori Nazionali del Gran Sasso in Italy. An analysis of 43.65 kg⋅d of data was made using a newly developed low energy trigger which was optimized to reduce the energy threshold of the detector. An upper limit of 0.58 c⋅kg −1 ⋅d −1 is established at 95% C.L., which translates into lower bounds f A ⩾ 3.12 × 10 5 GeV 95% C.L. (DFSZ model) and f A ⩾ 2.41 × 10 4 GeV 95% C.L. (KSVZ model) on the Peccei-Quinn symmetry-breaking scale, for a value of S = 0.5 of the flavor-singlet axial vector matrix element. These bounds can be expressed in terms of axion masses as m A ⩽ 19.2 eV and m A ⩽ 250 eV at 95% C.L. in the DFSZ and KSVZ models respectively. Bounds are given also for the interval 0.35 ⩽ S ⩽ 0.55.