Prof Roman Walczak

Abstract:

Intermittency effects have been studied directly for the first time in e+e- annihilation, using 37 509 hadronic events at an average CM energy of 〈√s〉=35 GeV. The factorial moments F2, F3 and F4 are given for the rapidity distribution and for the two-dimensional distributions in rapidity and azimuthal angle. The effects of cuts in sphericity and particle momentum are large. Comparison with several fragmentation models are made; some models like the Lund model with O(αs2) matrix element give a qualitative description of the phenomena. The importance of detector effects is demonstrated. The results are discussed in terms of various suggested interpretations of this effect. © 1989.

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.