Weak-interaction strength from charge-exchange reactions versus β decay in the A=40 isoquintet

We report a measurement of the Gamow-Teller (GT) strength distribution for Ar-40 -> K-40 using the 0(degrees)(p,n) reaction. The measurement extends observed GT strength distribution in the A=40 system up to an excitation energy of similar to 8 MeV. In comparing our results with those from the beta decay of the isospin mirror nucleus Ti-40, we find that, within the excitation energy region probed by the beta-decay experiment, we observe a total GT strength that is in fair agreement with the beta-decay measurement. However, we find that the relative strength of the two strongest transitions differs by a factor of similar to 1.8 in comparing our results from (p,n) reactions with the beta decay of Ti-40. Using our results we present the neutrino-capture cross section for Ar-40.