Experimental Aspects of Nuclear Matrix Elements for Double Beta Decays and Astro Neutrinos

We report briefly recent experimental studies of nuclear responses (square of nuclear matrix element NME) for astro-neutrinos and double beta decays (DBDs) by single EC/beta decays, charge exchange reactions (CERs) and ordinary muou captures (OMCs). The NMEs are shown to be uniformly reduced with respect to quasi-particle and pnQRPA NMEs in wide multipole and momentum regions. The reduction is expressed by the quenching coefficient g(A)(eff)/g(A). Impact of the reduction on astro-neutrino and DBD studies is discussed.