Professor Brian Foster OBE, FRS

Abstract:

The production of strange baryons in e+e- annihilation has been studied at centre of mass energies of 34.8 GeV and 42.1 GeV, using the TASSO detector at DESY. Inclusive cross-sections have been obtained for Λ0 and Ξ- production and an upper limit has been placed upon the production rate of Σ*±(1385). We measure the Λ0 multiplicity per event to be {Mathematical expression} and {Mathematical expression} at {Mathematical expression} and 42.1 GeV respectively. The Ξ- multiplicity per event is found to be {Mathematical expression} at {Mathematical expression}. An investigation has been made of the extent to which Λ0 are produced in pairs. The Λ0 cross-section has been studied as a function of event sphericity. © 1989 Springer-Verlag.

Abstract:

Data on jet masses, resulting from the decomposition of e+e- hadronic final states into two hemispheres, are presented at centre of mass energies between 12 and 43.5 GeV. Comparisons are made with bare O(αs2) QCD predictions as well as with QCD based fragmentation models. Values for αs and {Mathematical expression} are determined, both with and without hadronization effects included. Upper and lower limits for {Mathematical expression} independent of fragmentation models have been determined to be 0.480±0.025 GeV and 0.047±0.007 GeV respectively. © 1989 Springer-Verlag.

Abstract:

A b enrichment technique using the long B lifetime has been developed, by which ∼600 hadronic events with >65%b purity are obtained. The properties of the associated jets are studied, with comparisons made between them and those in hadronic data in which b quarks make up only 10% of the total, and jets in Monte Carlo events. The distributions in rapidity and multiplicity yield two new determinations of the fragmentation variable z for b hadrons and confirm that the b fragmentation function is hard. We also present the first measurement of the relative strength of the strong interaction coupling of the b quark compared with the average of all flavours. © 1989 Springer-Verlag.

Abstract:

We report on an analysis of the multiplicity distributions of charged particles produced in e+e- annihilation into hadrons at c.m. energies between 14 and 46.8 GeV. The charged multiplicity distributions of the whole event and single hemisphere deviate significantly from the Poisson distribution but follow approximate KNO scaling. We have also studied the multiplicity distributions in various rapidity intervals and found that they can be well described by the negative binomial distribution only for small central intervals. We have also analysed forward-backward multiplicity correlations for different energies and selections of particle charge and shown that they can be understood in terms of the fragmentation properties of the different quark flavours and by the production and decay of resonances. These correlations are well reproduced by the Lund string model. © 1989 Springer-Verlag.

Abstract:

Inclusive charged particle production in e+e- annihilation into hadrons is studied in terms of the particle fractional momentum xp. The xp distribution for gluon jets is extracted by comparing two data samples measured in the TASSO detector: nearly symmetric three jet events at centre-of-mass energy W∼35 GeV and two jet events at W∼22 GeV, yielding quark and gluon jets of similar energies (∼11.5 GeV). No significant difference is observed between quark and gluon jets. Monte Carlo models based on parton showers describe the trend and energy variation of the data better than a model with second order matrix element in αs. © 1989 Springer-Verlag.