Tau Kinematics from Impact Parameters

The momenta of $\tau$ decay products in the reaction $e^+e^-\to\tau^+\tau^-$ do not constrain the $\tau$ direction unambiguously. It is shown how the measurement of tracks of hadrons from semileptonic $\tau$ decays, in particular their relative impact parameters, allows to resolve this ambiguity.Comment: 4[pag]es, 1 figure available by FAX, TTP93-1

Semileptonic tau decays, structure functions, kinematics and polarisation

The most general angular distribution of two or three meson final states from semileptonic decays $\tau\rightarrow \pi\pi\nu$, $K\pi\nu$, $\pi\pi\pi\nu$, $K\pi\pi\nu$, $K\pi\nu$, $KKK\nu$, $\eta\pi\pi\nu,\,\ldots{}$ of polarized $\tau$ leptons can be characterized by 16 structure functions. Predictions for hadronic matrix elements, based on CVC and chiral Lagrangians and their relations to the structure functions are discussed. Most of them can be determined in currently ongoing high statistics experiments. Emphasis of the kinematical analysis is firstly put on $\tau$ decays in $e^{+}e^{-}$ experiments where the neutrino escapes detection and the $\tau$ rest frame cannot be reconstructed. Subsequently it is shown, how the determination of hadron tracks in double semileptonic events allows to fully reconstruct the $\tau$ kinematics. The implications for the spin analysis are indicated.Comment: 12 pages, LaTeX (uses epsf.sty, 3 ps-figures appended as extra uuencoded file) The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ttp94-27/ttp94-27.ps, or via www at http://ttpux2.physik.uni-karlsruhe.de/preprints.htm

V-a Tests Through Leptons from Polarised Top Quarks

Angular-energy distributions are studied for charged leptons and neutrinos from the decays of polarised top quarks. A small admixture of V+A interactions is incorporated. The polarisation dependent part of the neutrino distribution which can be measured experimentally through the missing momentum is particularly sensitive towards deviations from the V-A structure. This result remains unaffected by QCD corrections which, however, cannot be neglected in a quantitative analysis.Comment: 10 pages, LaTex (uses epsf.sty, 2 figures appended as uuencoded ps files). A complete postscript file, including figures, is available via anonymous ftp at ttpux2.physik.uni-karlsruhe.de (129.13.102.139) as /ttp94-4/ttp94-4.ps, Local preprint# TTP94-

Exotic Bound State Production at Hadron Colliders

Hadronic production of nonrelativistic boundstates of $b^{\prime}$ or isosinglet quarks D with suppressed weak decays is investigated for LHC and SSC energies. QCD corrections to production and decay rates are incorporated. Large rates for final states from $\eta_{b^{\prime}}\rightarrow HZ$ are predicted.Comment: 7 pages and 13 figures (figures not includes, can be sent upon request), TTP93-1

Measuring sigma(e+ e- --> hadrons) with Tagged Photons at Electron Positron Colliders

A Monte Carlo generator has been constructed to simulate the reaction e+ e- --> gamma + 2 pions and gamma + 4 pions, where the photon is assumed to be observed in the detector. Predictions are presented for cms energies of 1GeV, 3GeV and 10GeV, corresponding to the energies of DAPHNE, BEBC and of B-meson factories. The event rates are sufficiently high to allow for a precise measurement of R(Q^2) in the region of Q between approximately 1GeV and 2.5GeV. Estimates for the kinematic breaking of isospin relations between different channels as a consequence of the mass difference between charged and neutral pions are given.Comment: Latex, Talk Presented at the Sixth Workshop on Tau Lepton Physics, Victoria, Canada, The complete paper is also available via the www at http://www-ttp.physik.uni-karlsruhe.de/Preprints

Fermionic and Scalar Corrections for the Abelian Form Factor at Two Loops

Two-loop corrections for the form factor in a massive Abelian theory are evaluated, which result from the insertion of massless fermion or scalar loops into the massive gauge boson propagator. The result is valid for arbitrary energies and gauge boson mass. Power-suppressed terms vanish rapidly in the high energy region where the result is well approximated by a polynomial of third order in ln(s/M^2). The relative importance of subleading logarithms is emphasised.Comment: Latex, 10 pages, 5 figures. B. Feucht is B. Jantzen in later publications. (The contents of the paper is unchanged.