A first measurement of the Lambda(Lambda)over-bar and Lambda Lambda ((Lambda)over-bar(Lambda)over-bar) spin compositions in hadronic Z(0) decays

The spin composition of , Lambda Lambda and <(Lambda)over bar><(Lambda)over bar> pairs at low invariant mass values has been measured for the first time in multihadronic Z(0) decays with the OPAL detector at LEP. No single spin state has been observed in the sample, verifying that the low mass enhancement in this sample, attributed to local baryon number compensation, is not a resonance state. The fraction of the spin 1 contribution to the pairs was found to be consistent with the value 0.75, as expected from a statistical spin mixture. This may be the net effect of many different QCD processes which contribute to the hyperon anti-hyperon pair production. The spin composition of the identical Lambda Lambda and <(Lambda)over bar(Lambda)over bar> pairs, well above threshold, is found to be similar to that of the sample. A Lambda Lambda emitter dimension is estimated from the data assuming the onset of the Pauli exclusion principle near threshold.

Keywords:

LUND MONTE-CARLO

OPAL JET CHAMBER

MICROVERTEX DETECTOR

BARYON PRODUCTION

E+E-PHYSICS

FRAGMENTATION

LEP

A first measurement of the Lambda(Lambda)over-bar and Lambda Lambda ((Lambda)over-bar(Lambda)over-bar) spin compositions in hadronic Z(0) decays

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