A study of τ-lepton production in the CMS energy region from 14 to 46.8 GeV at PETRA is reported. The cross section, the decay branching ratio into μνν, and the electroweak parameters are determined with a total integrated luminosity of 115 pb−1.

We use the reaction e+e−→μ+μ−, in the Mark J detector at the DESY high-energy e+e− collider PETRA, to test the standard electroweak theory and find good agreement. We also set limits on the parameters of several extended gauge theories.Received 30 May 1985DOI:https://doi.org/10.1103/PhysRevLett.55.665©1985 American Physical Society

PETRA, the e+e− collider, has operated at a maximum CM energy of 46.78 GeV. We update our previous results on new particle searches and set significantly better mass limits on some.

We have searched for resonances in the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}, \ensuremath{\gamma}\ensuremath{\gamma}, \ensuremath{\mu}\ensuremath{\mu}, \mathrm{and} \mathrm{ee}$, in the energy range $39.79<\sqrt{s}<45.52$ GeV, using the Mark J detector at PETRA. We obtain stringent upper limits on the production of toponium and particles postulated to explain ${Z}^{0}\ensuremath{\rightarrow}\mathrm{lepton}\mathrm{pair}+\ensuremath{\gamma}$ events observed at the CERN $\stackrel{-}{p}p$ collider. We also set limits on the mass and coupling constant of excited electrons.

We report mass limits on the ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}^{0}$ and ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{W}}^{\ifmmode\pm\else\textpm\fi{}}$, supersymmetric partners of the ${Z}^{0}$ and ${W}^{\ifmmode\pm\else\textpm\fi{}}$, respectively, using the MARK-J detector at PETRA. The experimental signatures in both cases are acoplanar lepton pairs with missing energy. For the ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{W}}^{\ifmmode\pm\else\textpm\fi{}}$, an additional signature is a single energetic lepton. No evidence is found for either the ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}^{0}({M}_{{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{Z}}^{0}}<35\mathrm{GeV})$ or the ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{W}}^{\ifmmode\pm\else\textpm\fi{}}({M}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{W}}<25\mathrm{GeV})$.

The two-loop massive operator matrix elements for the fermionic local twist-2 operators with external massive fermion lines in Quantum Electrodynamics (QED) are calculated up to the constant terms in the dimensional parameter ε=D−4. We investigate the hypothesis of Berends et al. (1988) [1] that the 2-loop QED initial state corrections to e+e− annihilation into a virtual neutral gauge boson, except power corrections of O((mf2/s)k), k⩾1, can be represented in terms of these matrix elements and the massless 2-loop Wilson coefficients of the Drell–Yan process.

With use of the MARK-J detector at $\sqrt{s}=34.7$ GeV 21 000 ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadron}$ events have been collected. By measurement of the asymmetry in angular energy correlations the strong coupling constant ${\ensuremath{\alpha}}_{s}=0.13\ifmmode\pm\else\textpm\fi{}0.01 (\mathrm{statistical})\ifmmode\pm\else\textpm\fi{}0.02 (\mathrm{systematic})$ is determined, in complete second order, and independent of the fragmentation models and QCD cutoff values used.

With a PETRA energy scan in \ensuremath{\le}30-MeV steps, the continuum production of open top quark up to 38.54 GeV is excluded. Over regions of energy scan from 29.90 to 38.63 GeV limits are set on the product of hadronic branching ratio and electronic width ${B}_{h}{\ensuremath{\Gamma}}_{\mathrm{ee}}$ for toponium to be less than 2.0 keV at the 95% confidence level. By a search for flavor-changing neutral currents in $b$ decay, models without a top quark are excluded.

The results of a high-statistics study of inclusive muon spectra at PETRA are reported. Improved mass limits have been obtained for heavy quarks, heavy leptons, and charged Higgs particles. It is shown that the fragmentation properties of b quarks and c quarks are different, with the mean fragmentation variables 〈zb〉=0.75±0.03±0.06, 〈zc〉=0.46±0.02±0.05 and the average semileptonic branching ratio for the B and C hadrons R(B)=(10.5±1.5±1.3)%, R(C)=(11.5±1.0±1.7)%.Received 22 April 1983DOI:https://doi.org/10.1103/PhysRevLett.51.443©1983 American Physical Society

The results of a high-statistics study of inclusive muon spectra at PETRA are reported. Improved mass limits have been obtained for heavy quarks, heavy leptons, and charged Higgs particles. It is shown that the fragmentation properties of b quarks and c quarks are different, with the mean fragmentation variables = 0.75 +- 0.03 +- 0.06, = 0.46 +- 0.02 +- 0.05 and the average semileptonic branching ratio for the B and C hadrons BR(B) = (10.5 +- 1.5 +- 1.3)%, BR(C) = (11.5 +- 1.0 +- 1.7)%.

We have performed a high statistics measurement of the production rate and the energy flow pattern of hadron events between √s=33 and 36.7 GeV. The data show no evidence for the production of a new quark with charge 23e. Planar events in e+e−→hadrons are shown to have three well separated jets. The production rate and the shape of three-jet events are compared with many models and we find that only the QCD model can explain the data.

The measurement of the nonelectromagnetic forward-backward charge asymmetry in the reaction e+eiz'tz at ~s-34.6 GeV and in the angular region 0& IcosOI&0.8 is re- ported.With a systematic error less than 1%, we observe an asymmetry of (-8.1+2.1)/p.This is in agreement with the standard electroweak theory prediction of (-7.6+ 0.6)%.The weak-current coupling constants are also reported.