Mirror-symmetry structure ofA=27,T=1/2nuclei studied through strong, weak, and electromagnetic interactions

Gamow-Teller (GT) transitions and $M1\mathrm{}$ transitions from or to the ground states are analogous in the pair of $T=1/2\mathrm{}$ mirror nuclei, if the excited states hold the mirror-symmetry properties. In order to study the mirror-symmetry structure of the $A=27\mathrm{}$ mirror nuclei ${}^{27}\mathrm{Al}$ and ${}^{27}\mathrm{Si},$ experimental data on GT transition strengths obtained from ${}^{27}{\overrightarrow{\mathrm{Si}}}^{27}\mathrm{Al}$ $\beta$ decay and from a good-resolution ${}^{27}\mathrm{Al}{(}^3\mathrm{He}{,t)}^{27}\mathrm{Si}$ reaction at 150 MeV/nucleon and 0° have been compared with $M1\mathrm{}$ transition strengths obtained from $\gamma$ decay in ${}^{27}\mathrm{Al}$ and ${}^{27}\mathrm{Al}(\gamma ,{\gamma }^{\prime })$ reaction. Good overall correspondence of transitions is observed for states up to nearly 9 MeV in excitation energy, where the particle-decay channel becomes important. The difference of excitation energies of analog states in the mirror nuclei are about 250 keV at this excitation energy. From a comparison of $B\left(M1\mathrm{}\right)\mathrm{}$ and $B\left(\mathrm{GT}\right)$ strengths of the analogous transitions, the contribution of the isoscalar and the orbital terms in the $M1\mathrm{}$ operator is found to become prominent in weak $M1\mathrm{}$ transitions.