M. Govan

An enhancement in the ΛΛ invariant mass spectrum

Abstract A 2.1 GeV/ c K − exposure in a heavy liquid bubble chamber has been used to search for the final states KΛΛ. An enhancement in the ΛΛ invariant mass spectrum at 2370 MeV/ c 2 is interpreted as a possible resonance produced in Ξ-nucleon interactions. An estimate of the cross-section for ΛΛ production in Ξ-nucleus reations is given.

A measurement of the Ξ hyperon lifetimes and α parameters

In an experiment using a heavy liquid bubble chamber the Ξ hyperon lifetimes and α parameters were measured to be τΞo = (3.04 ± 0.230.26) × 10−10 sec, τΞ− = (1.73 ± 0.070.08) × 10−10 sec, αΞo = −0.84 ± 0.27 and αΞ− = −0.42 ± 0.11. These values agree with measurements which employed different techniques and are consistent with the predictions of the ΔI = 12 rule.

A search for the radiative decay Y0*(1327) → Λγ

Abstract A 2.1 GeV/ c K − exposure in a heavy-liquid bubble chamber has been used to search for the final state Y ∗ (1327) → Λγ . No evidence was found for the existence of this state; an upper limit is placed on the cross-section of the reaction K − + p → Y ∗ (1327) + π + + π − + nπ o , n ⩾ 0 .

The mass and width of the ξ(1530)

Abstract 286 ξ O (1530) and 185 ξ − (1530) events corresponding to production cross sections of 29 μb and 26 μb respectively are analysed for mass, width and electromagnetic mass difference. The distribution of invariant mass errors and important systematic effects are included in the analysis. A width of 11.0 ± 1.8 MeV for the ξ O (1530) and of 16.2 ± 4.6 for ξ − (1530) are obtained. The former is in some disagreement with the presently accepted value of 7.3 ± 1.7 MeV whilst the latter is the only such reported measurement to date, and these new values bring the world average value into closer agreement with the prediction of unbroken SU(3). Corresponding masses are 1532.3 ± 0.7 MeV and 1536.2 ± 1.6 MeV giving a mass difference of ΔM = 3.9 ± 1.8 MeV and lead to a world average value of ΔM of 4.3 ± 1.3 MeV. Some conclusions regarding measurement of resonant widths are made.

The masses of the Ξ hyperons

Abstract Using a 2.1 GeV/ c K − exposure in a heavy liquid bubble chamber, the masses of the Ξ hyperons have been measured to be M ( Ξ 0 ) = 1315.2 ± 0.9 MeV/ c 2 and M ( Ξ − ) = 1321.12± 0.41 MeV/ c 2 . Their mass difference is compared to theoretical predictions.