Tensor-Force Effects on thel-ForbiddenM1Transitions

The reduced matrix elements for the $l$-forbidden $M1\mathrm{}$ transitions are calculated in the frame-work of the pairing model. Three quasiparticle states are admixed to the seniority-one state by perturbation due to the short range $\delta$ force and the tensor force. It is shown that the mixing of the tensor force is essential to explain the observed values of the reduced matrix elements.