On heavy unstable particles produced in high energy nuclear disintegrations

The results of a systematic investigation into the production of heavy unstable particles in energetic nuclear disintegrations is reported. Mass measurements by the grain density-range method have been made in order to detect K-mesons independently of any secondary effects. Measurements were made on tracks which satisfied certain geometrical criteria and which originated in disintegrations of energy greater than ∼2 GeV. The velocity range studied for K-mesons was from 0.25c to 0.56c. Ten K-mesons and two hyperons were found. The two hyperons and one of the K-mesons decayed in flight. All the particles decayed into single charged secondaries. Both hyperons were emitted from disintegrations which also produced K-mesons. These associated pairs have been reported previously (1). The results are consistent with the view that hyperons and heavy mesons are mainly produced in association, and that, in the energy range considered, K-mesons show a large charge disparity. Two additional hyperons were found one of which appears to be an example of the decay scheme Y± → Λ0 + π± + ∼60 MeV. A value for the lifetime of the hyperons is estimated from six suitable examples found in this laboratory. Mass measurements have been made on the tracks of 17 K-mesons. The mean value obtained is 985 ± 16 me.