Pinning down the strength function for ordinary muon capture on 100Mo

Abstract

Ordinary muon capture (OMC) on 100Mo is studied both experimentally and theoretically in order to access the weak responses in wide energy and momentum regions. The OMC populates states in 100Nb up to some 50 MeV in excitation energy. For the first time the associated OMC strength function has been computed and compared with the obtained data. The present computations are performed using the Morita-Fujii formalism of OMC by extending the original formalism beyond the leading order. The participant nuclear wave functions are obtained in extended no-core single-particle model space using the spherical version of proton-neutron quasiparticle random-phase approximation (pnQRPA) with two-nucleon interactions based on the Bonn one-boson-exchange G matrix. Partial restoration of the isospin symmetry is implemented in the calculations by separately fitting the isoscalar and isovector parts of the particle-particle interaction strength of pnQRPA. Both the computed and experimental OMC strength distributions show a giant resonance at around 12 MeV. Further measurements and calculations of the OMC strength functions for double-beta-decay daughter nuclei could enable access to in-medium renormalization of the weak axial couplings and pave the way to improved accuracy of the double-beta-decay nuclear matrix elements.