$\boldsymbol R_{\boldsymbol g}$ = $\boldsymbol G_{\boldsymbol C}$ $/$ $\boldsymbol G_{\boldsymbol F}$
INSPIRE search
The effective Lagrangian for the ${{\mathit \mu}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \mu}^{-}}{{\mathit e}^{+}}$ conversion is assumed to be
$\cal L$ = 2${}^{−1/2}$ $\mathit G_{\mathit C}$ [${{\overline{\mathit \psi}}_{{\mu}}}{{\mathit \gamma}_{{\lambda}}}$ (1 $−$ ${{\mathit \gamma}}_{5}$) ${{\mathit \psi}_{{e}}}$] [${{\overline{\mathit \psi}}_{{\mu}}}{{\mathit \gamma}_{{\lambda}}}$ (1 $−$ ${{\mathit \gamma}}_{5}$) ${{\mathit \psi}_{{e}}}$] $+$ h.c.
The experimental result is then an upper limit on $\mathit G_{\mathit C}/\mathit G_{\mathit F}$, where $\mathit G_{\mathit F}$ is the Fermi coupling constant.
