A new experiment for determining the upper limit for the branching ratio $R$ of the process ${\mu }^{+}\to e^{+}+\gamma$ relative to the normal decay mode ${\mu }^{+}\to e^{+}+\nu +\overline{\nu }$ yields a value of $R$ of less than 1.2×${10}^{-6\mathrm{}}$ with a 90% confidence level.

• Received 4 November 1959

DOI:https://doi.org/10.1103/PhysRev.118.589