241 research outputs found
Tau Kinematics from Impact Parameters
The momenta of decay products in the reaction
do not constrain the direction unambiguously. It is shown how the
measurement of tracks of hadrons from semileptonic decays, in particular
their relative impact parameters, allows to resolve this ambiguity.Comment: 4[pag]es, 1 figure available by FAX, TTP93-1
QCD Corrections to Electroweak Annihilation Decays of Superheavy Quarkonia
QCD corrections to all the allowed decays of superheavy groundstate quarkonia
into electroweak gauge and Higgs bosons are presented. For quick estimates,
approximations that reproduce the exact results within less than at worst two
percent are also given.Comment: 20 pages RevTeX, 9 figures. The complete paper, including figures, is
also available via anonymous ftp at (129.13.102.139) as
ftp://ttpux2.physik.uni-karlsruhe.de/ttp95-05/ttp95-05.ps, or via www at
http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints
Semileptonic tau decays, structure functions, kinematics and polarisation
The most general angular distribution of two or three meson final states from
semileptonic decays , , ,
, , , of polarized
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 decays in
experiments where the neutrino escapes detection and the rest frame
cannot be reconstructed. Subsequently it is shown, how the determination of
hadron tracks in double semileptonic events allows to fully reconstruct the
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
Gluon Fragmentation into Heavy Quarkonium
The dominant production mechanism for heavy quark-antiquark bound states in
very high energy processes is fragmentation, the splitting of a high energy
parton into a quarkonium state and other partons. We show that the
fragmentation functions describing these processes can be calculated
using perturbative QCD. We calculate the fragmentation functions for a gluon to
split into S-wave quarkonium states to leading order in the QCD coupling
constant. The leading logarithms of , where is the factorization
scale and is the heavy quark mass, are summed up using Altarelli-Parisi
evolution equations.Comment: LateX 11 pages (3 figures available upon request). NUHEP-TH-92-2
Electroweak effects in top-quark pair production at Hadron Colliders
Top-quark physics plays an important role at hadron colliders such as the
Tevatron collider at Fermilab or the upcoming Large Hadron Collider (LHC) at
CERN. Given the planned experimental precision, detailed theoretical
predictions are mandatory. In this article we present analytic results for the
complete electroweak corrections to gluon induced top-quark pair production,
completing our earlier results for the quark-induced reaction. As an
application we discuss top-quark pair production at Tevatron and at LHC. In
particular we show that, although small for inclusive quantities, weak
corrections can be sizeable for differential distribution
Measuring sigma(e^+e^- \to hadrons) using tagged photon
We propose to use events with radiated photons in e^+e^- collisions to
measure the total cross section of e^+ e^- \to hadrons as a function of the
center of mass energy. The Monte Carlo simulation for the collider DAPHNE shows
that a competitive accuracy can be achieved with this method.Comment: revtex, 13 page
Exotic Bound State Production at Hadron Colliders
Hadronic production of nonrelativistic boundstates of 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 are predicted.Comment: 7 pages and 13 figures (figures not includes, can be sent upon
request), TTP93-1
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-
Tau Polarimetry with Multi Meson States
It is demonstrated that the analyzing power of multi-meson final states in
semileptonic decays with respect to the spin is equal and maximal
for all decay modes.Comment: 4 pages, LaTex. The complete paper is also available via anonymous
ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at
http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints
The Impact of Measurements at Intermediate Energies on the Parameters of the Standard Model
We discuss the impact of precision measurements of in the center-of-mass range between 3 and 12 GeV, including
improvements in the electronic widths of the narrow charmonium and bottonium
resonances, on the determination of parameters of the Standard Model. In
particular we discuss the impact of potential improvements on the extraction of
the strong coupling constant , on the evaluation of the hadronic
contributions to the electromagnetic coupling , and the
determination of the charm and bottom quark masses.Comment: 8 page
- …