We present an analysis of electroweak leptonic couplings from high statistics experiments on Bhabha scattering and μ pair production at an energy of 34.5 GeV. The forward-backward charge asymmetry of the μ pairs was measured to be −0.098±0.023±0.005. The data were found to agree well with the standard theory of electroweak interaction giving sin2θW=0.27±0.07. The leptonic weak couplings were determined to begv=0.000±0.170 andgA=−0.481±0.055. The data were also used to investigate a class of composite models for leptons.
No description provided.
No description provided.
We have measured the reactions e + e − → e + e − → μ + μ − and e + e − → γγ at c.m. energies between 12 and 31.6 GeV. Excellent agreement with the predictions of QED has been found, resulting in cut off parameters Λ + > 112 GeV and Λ − > 139 GeV for the first process and Λ + > 34 GeV and Λ − > 42 GeV (95% c.1.) for the last one. A limit on the Weinberg angle of sin 2 θ W < 0.55 (95% c.1.) has been obtained.
SIG(C=QED) QED predictions for the cross sections. Only statistical errors are given.
SIG(C=QED) QED predictions for the cross sections. Only statistical errors are given.
SIG(C=QED) QED predictions for the cross sections. Only statistical errors are given.
We have measured the cross sections for e + e − → e + e − , e + e − → μ + μ − , e + e − → γγ and e + e − → hadrons in an energy scan at center of mass energies between 39.79 and 46.72 GeV in 30 MeV steps. New spinless bosons, whose existence has been postulated as a possible means to explain the anomalously large radiative width of the Z 0 found at the CERN SPS p p collider, are ruled out in the scan region. The data are used to set limits on the couplings to lepton, photon and quark pairs of bosons with masses above 46.72 GeV.
SIG(C=SM) is the Standard Model predicted cross section.
The process γγ→π+π−π+π− has been investigated in reactions of the typee+e−→e+e−π+π−π+π− in the single tag mode. The range of the four momentum squared of one of the virtual photons was 0.28 GeV2/c2≦Q2≦3.6 GeV2/c2, the average being 〈Q2〉=0.92 GeV2/c2; the other photon was quasi real. The reaction is mainly described by the channels γγ→ρ0ρ0 and γγ→4π (phase space), occuring with about equal probability. TheQ2-dependence of the cross section is in agreement with the ρ form factor.
Data read from graph.. Additional overall systematic error 25%.
Data read from graph.. Additional overall systematic error 25%.. The Q**2 approx 0 datum is deduced from the earlier TASSO paper, Brandelik et al, Phys. Lett. 97B(1980)448, (<a href=http://durpdg.dur.ac.uk/scripts/reacsearch.csh/TESTREAC/red+1151> RED = 1151 </a>) on rho0 rho0 production.
The production of electrons by bottom and charm hadrons has been studied in e + e − annihilation at 34.6 GeV center of mass energy. It is observed that the b quark fragmentation function is peaked at large values of the scaling variable z with 〈 z b 〉 = 0.84 +0.15 + 0.15 −0.10 − 0.11 . For c quarks 〈 z c 〉 = 0.57 +0.10 + 0.05 −0.09 − 0.06 is observed. A forward-backward charge asymmetry of A = −0.25 ± 0.22 was measured in b production.
THE VALUE OF ASYMMETRY WAS DETERMINED USING A SAMPLE OF PROMPT ELECTRONS.
THE VALUE OF ASYMMETRY WAS DETERMINED USING A SAMPLE OF PROMPT ELECTRONS.
The production of prompt muons ine+e− annihilation has been studied at centre of mass energies near 34.5 GeV. The measured semi-muonic branching ratios ofb andc quarks areB(b»Xμv) =0.117±0.028±0.01 andB(c→Xμv)=0.082 ±0.012a−0.01+0.02. The fragmentation functions of heavy quarks are hard, <zb>=0.85a−0.12–0.07+0.10+0.02 and <zc> =0.77a−0.07–0.11+0.05+0.03. Limits have been set on flavour changing neutral current decays:B(b→Xµ+µ−) <0.02 andB(b→Xµ+µ− (95% confidence level).
THE VALUE OF ASYMMETRY WAS DETERMINED USING A SAMPLE OF PROMPT MUONS.
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\((\sigma _{D^{* + } }+ \sigma _{D^{* - } } )/\sigma _{\mu \mu }= 1.28 \pm 0.09 \pm 0.18\) 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\(\tau _{D^0= } (4.8 \pm _{0.9 - 0.7}^{1.0 + 0.5} )10^{ - 13} s\).
Cross sections using D0 --> K- PI+ channel.
Cross sections using D0 --> K- PI+ PI- PI+ channel.
No description provided.
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 andpt2 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.
Scaled differential cross sections for K0 production. Errors are statistical and systematic combined.
Scaled differential cross section for K0 production. Errors are statistical and systematic combined.
Scaled differential cross section for K0 production. Errors are statistical and systematic combined.
We have observed τ pair production at average CM energies of 13.9, 22.3, 34.5 and 43.1 GeV. The cross-sections are consistent with QED, the cut off parameters beingΛ+>161 GeV andΛ−169 GeV (95% CL). The topological branching fraction of the τ to 1 charged particle,B1, is 0.847±0.011 (stat)−0.013+0.016(syst) and no decays to 5 charged particles were observed resulting inB5<0.007 (95% CL). Within the 3 charged track final stateB(τ−→π−π+π−v)/(B(τ−→π−π+π−v)+B(τ−→π−π+π−π0v))=0.37−0.20+0.35
No description provided.
No description provided.