Professor Brian Foster OBE, FRS

Abstract:

The average lifetime of B hadrons has been measured by the TASSO collaboration using 110 pb-1 of data collected in 1986 at a center of mass energy of 35 GeV. Measurements by three different methods are presented and a method of B-enrichment is discussed. The result of the impact parameter method is τB=1.36±0.13±0.28 ps, that of the vertex method is τB=1.30±0.10±0.28 ps and that of the dipole method is τB=1.47±0.14±0.30 ps. These are combined to give the result τB=1.35±0.10±0.24 ps. © 1989 Springer-Verlag.

Abstract:

The inclusive production of π± and K± mesons and of protons and antiprotons in e+e- annihilations has been measured at 34 GeV and 44 GeV center of mass energy; in addition π± mesons have been measured at 44 GeV c.m. energy. Differential cross sections and particle yields are given. At 34 GeV average multiplicities are: {Mathematical expression} and at 44 GeV: {Mathematical expression} © 1989 Springer-Verlag.

Abstract:

We report on a study of inclusive production of D*± mesons in e+e- annihilation at c.m. energies between 28 and 46.8 GeV using the TASSO detector at the PETRA storage ring. A hard D*± energy spectrum is measured with a maximum near ED*±≃0.6 Ebeam. The measured cross section ratio {Mathematical expression} indicates that D* production accounts for a large fraction of the observed charm production. Two complementary methods have been used to determine the forward-backward asymmetry of charm pair production due to electroweak interference. Combining both measurements the product of the axial vector couplings of the electron and the charm quark to the weak neutral current was determined to be gAegAc=-(0.276±0.073), in agreement with the standard model prediction of -0.25. Using a sample of reconstructed D*± mesons, the relative strength of the strong interaction coupling of the c quark compared to that of an average of all flavours is measured as αs(c)/αs(all)=0.91±0.38±0.15, consistent with the coupling constant being flavour independent. An update of our D0 lifetime measurement is presented, based on a considerable increase in statistics, the final result being {Mathematical expression}. © 1989 Springer-Verlag.

Abstract:

Production of the ηc meson in e+e- quasireal two photon collisions has been looked for in three channels. The data were obtained from an integrated luminosity of 189 pb-1. An ηc signal is observed in two decay modes (Ks0K±π∓,π+π-π+π-) with a combined statistical significance of 3.5 standard deviations. Using the known ηc branching ratios to these channels and to K+K-π+π- the combined partial ηc width to γγ is Γγγ(ηc). The first error is statistical, and the second one includes the systematic and branching ratio errors. Calculated as an upper limit we obtain Γγγ(ηc) (95% C.L., including the systematic error). © 1989 Springer-Verlag.