Nuclear muon capture byHe3: Meson exchange currents for the triton channel

We have calculated exchange corrections for nuclear muon capture by ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ leading to the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ final state using the hard-pion model and realistic nuclear wave functions. These currents modify the vector and axial part of the weak nuclear current. In their absence the rate is 12% smaller than found by experiment. Our final result for the rate is 1502±32 per second. For the analyzing powers we find ${\mathit{A}}_{\mathit{v}}$=0.515±0.005, ${\mathit{A}}_{\mathit{t}}$=-0.375±0.004, and ${\mathit{A}}_{\mathrm{\Delta }}$=-0.110±0.006. These predictions use the PCAC value of ${\mathit{g}}_{\mathit{P}}$. The variation of the observables with ${\mathit{g}}_{\mathit{P}}$ is also reported. © 1996 The American Physical Society.