Production of charmed mesons in γγ-interactions at PETRA energies has been observed in the TASSO detector. Cross sections for inclusiveD*± and\(D^0 \bar D^0 \) production have been measured. Neutral and charged meson pairs are estimated to be produced with comparable cross sections, and their sum seems to account for a sizeable fraction of σtot(γγ→hadrons) near the\(c\bar c\) threshold.

The forward-backward asymmetry in the reaction e+e-→bb has been determined at centre of mass energies near 35 GeV using the TASSO detector. We report results from three different methods. The combined result of the measurements is\(\overline A _b = - 0.21 \pm 0.08\) ignoring\(B^0 \bar B^0 \) mixing. Taking mixing into account leads to a corrected asymmetry of\(\overline {A_b^{cor} } = - 0.28 \pm 0.11\). The axial vector coupling constant of theb quark as calculated from the corrected asymmetry isab=−1.2±0.5 to be compared with the valuea b SM =−1 from the standard model.

The full TASSO data have been used to study the inclusive production of strange mesons ine+e− annihilations. Differential and total cross sections have been measured in the centre of mass energy range 14 to 44 GeV forK0,\(\bar K^0\) and 34.5 to 44 GeV forK*± (892). We have investigated the strange meson production properties in jets by studying the rapidity andp t 2 distributions as well as the evolution of the multiplicities as a function of the event sphericity. We find no evidence that the strange meson yields increase with increasing sphericity faster than the total charged multiplicity.

Jet properties ine+e- annihilation at center of mass energies of 14, 22, 35 and 43.7 GeV were studied with the data collected in the TASSO detector at PETRA, using the same evaluation procedures for all the energies. The total hadronic cross section ratio for the center of mass energy interval 39–47 GeV was determined to be R=4.11±0.05 (stat)±0.18(syst.) at <img src="/fulltext-image.asp?format=htmlnonpaginated&src=HUX002565822M488_html\10052_2005_Article_BF01552339_TeX2GIFIE1.gif" border="0" alt=" $$\langle \sqrt s \rangle = 43 - 7$$ " /> GeV. Corrected distributions of global shape variables are presented as well as the inclusive charged particle distributions for scaled momentum and transverse momentum. The center of mass energy evolution of the average sphericity, thrust, aplanarity and particle momentum is shown.

The forward-backward asymmetry in the reaction e+e-→bb has been determined at centre of mass energies near 35 GeV using the TASSO detector. We report results from three different methods. The combined result of the measurements is <img src="/fulltext-image.asp?format=htmlnonpaginated&src=J3312M2803551688_html\10052_2005_Article_BF01572023_TeX2GIFIE2.gif" border="0" alt=" $$\overline A _b = - 0.21 \pm 0.08$$ " /> ignoring <img src="/fulltext-image.asp?format=htmlnonpaginated&src=J3312M2803551688_html\10052_2005_Article_BF01572023_TeX2GIFIE3.gif" border="0" alt=" $$B^0 \bar B^0 $$ " /> mixing. Taking mixing into account leads to a corrected asymmetry of <img src="/fulltext-image.asp?format=htmlnonpaginated&src=J3312M2803551688_html\10052_2005_Article_BF01572023_TeX2GIFIE4.gif" border="0" alt=" $$\overline {A_b^{cor} } = - 0.28 \pm 0.11$$ " />. The axial vector coupling constant of theb quark as calculated from the corrected asymmetry isab=−1.2±0.5 to be compared with the valueabSM=−1 from the standard model.

The full TASSO data have been used to study the orientation of three-jet events ine+e− annihilation. The polar angle distributions of the normal to the three-jet plane as well as the polar angle distribution of the most energetic jet have been measured as a function of the thrust cut-off used to select the three-jet sample. The data corrected for radiation and detector effects are compared to QCD predictions and fair agreement is found. As a consistency check we also present measurements of the azimuthal correlations between the lepton and hadron planes. A significant azimuthal dependence is found, consistent again with the QCD predictions.

We report on a study of inclusive production ofD*± mesons ine+e− annihilation at c.m. energies between 28 and 46.8 GeV using the TASSO detector at the PETRA storage ring. A hardD*± energy spectrum is measured with a maximum nearED*±≃0.6Ebeam. The measured cross section ratio <img src="/fulltext-image.asp?format=htmlnonpaginated&src=U564651613106L43_html\10052_2005_Article_BF01415550_TeX2GIFIE2.gif" border="0" alt=" $$(\sigma _{D^{* + } } + \sigma _{D^{* - } } )/\sigma _{\mu \mu } = 1.28 \pm 0.09 \pm 0.18$$ " /> indicates thatD* 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 begAegAc=−(0.276±0.073), in agreement with the standard model prediction of −0.25. Using a sample of reconstructedD*± mesons, the relative strength of the strong interaction coupling of thec 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 ourD0 lifetime measurement is presented, based on a considerable increase in statistics, the final result being <img src="/fulltext-image.asp?format=htmlnonpaginated&src=U564651613106L43_html\10052_2005_Article_BF01415550_TeX2GIFIE3.gif" border="0" alt=" $$\tau _{D^0 = } (4.8 \pm _{0.9 - 0.7}^{1.0 + 0.5} )10^{ - 13} s$$ " />.

Data on jet masses, resulting from the decomposition ofe+e− hadronic final states into two hemispheres, are presented at centre of mass energies between 12 and 43.5 GeV. Comparisons are made with bareO(α s 2 ) QCD predictions as well as with QCD based fragmentation models. Values for α s and\(\Lambda _{\overline {MS} } \) are determined, both with and without hadronization effects included. Upper and lower limits for\(\Lambda _{\overline {MS} } \) independent of fragmentation models have been determined to be 0.480±0.025 GeV and 0.047±0.007 GeV respectively.

The average lifetime ofB 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 ofB-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.

Inclusive charged particle production ine + e − annihilation into hadrons is studied in terms of the particle fractional momentumx p . Thex p 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 energyW∼35 GeV and two jet events atW∼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 α s .

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.

We report on an analysis of the multiplicity distributions of charged particles produced ine + 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.

Ab enrichment technique using the longB 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 whichb 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 variablez forb hadrons and confirm that theb fragmentation function is hard. We also present the first measurement of the relative strength of the strong interaction coupling of theb quark compared with the average of all flavours.