Mass of the ChargedΣHyperons

Twenty-nine examples of ${\Sigma }^{+}$ hyperon decays at rest into protons were used to determine the mass of the ${\Sigma }^{+}$ hyperon. The stopping power for each batch of emulsions containing these events was determined by making use of ${\mu }^{+}$-meson ranges obtained from the decay of ${\pi }^{+}$-mesons at rest. The mean range of protons from ${\Sigma }^{+}$ decays was found to be 1686.5±6.0 microns. The rms deviation was 37.2±6.0 microns. The $Q$ value for the decay (${\Sigma }^{+}\to p+{\pi }^0$) was found to be 116.37±0.4 Mev and the mass of the ${\Sigma }^{+}$ hyperon, $(2328.1\mathrm{}\pm 0.8)m_e$. An analysis of three collinear events, which resulted from the interaction of stopped $K^{-}$ mesons with hydrogen nuclei of the emulsion, gave the ${\Sigma }^{-}$ hyperon mass to be $(2341.6\mathrm{}\pm 2.0)m_e$ and the mass difference between ${\Sigma }^{-}$ and ${\Sigma }^{+}$ hyperons $(13.5\mathrm{}\pm 2.0)m_e$.