Search for a Neutral Boson in a Two-Body Decay ofK+→π+X0

Abstract

The momentum spectrum of the ${\ensuremath{\pi}}^{+}$ in stopping ${K}^{+}$ decays was measured by use of a high-resolution magnetic spectrometer to search for a discrete peak due to a neutral boson ${X}^{0}$ in a two-body decay ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{X}^{0}$. An upper bound of the branching ratio $R({K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{X}^{0})$ is presented for the mass range of ${X}^{0}$ from 10 to 300 MeV/${\mathit{c}}^{2}$.