Repolarization of Negative Muons by Polarized ${}^{209}$Bi Nuclei

Abstract

A large ${\mu }^{-}$ polarization was achieved in muonic Bi atoms with the help of the strong hyperfine field in a polarized nuclear target. Using ${}^{209}$Bi nuclei polarized to ($59\pm 9$)% in ferromagnetic BiMn, we observed a $\mu$-$e$ decay asymmetry of ($13.1\pm 3.9$)%, which gives ${\mu }^{-}$ polarization per nuclear polarization equal to $-1.07\pm 0.35$. This value is almost consistent with $-0.792$ calculated for nuclei with spin $I=\frac{9}{2}$ and a positive magnetic moment under the assumption that the hyperfine interaction becomes effective in the lowest muonic states.

Corrected version of original paper, 4 pages, 2 figures, corrections indicated by red