4,285 research outputs found
12 Years of Precision Calculations for LEP. What's Next?
I shortly review time period of twelve years, 1989-2000, which was devoted to
a theoretical support of experiments at LEP and SLC at Z resonance and discuss
several directions of possible future work in the field of precision
theoretical calculations for experiments at future colliders.Comment: 11 Latex, including 1 figures. Updated version as appeared in the
Journa
Off shell W pair production in e+ e- annihilation: The CC11 process
The various four-fermion production channels in annihilation are
discussed and the {\tt CC11} process , {\mbox{}}, is studied in detail. The cross
section , with being the invariant masses squared
of the two fermion pairs, may be expressed by six generic functions. All but
one may be found in the literature. The cross section, including initial state
radiation and the Coulomb correction, is discussed and compared with other
calculations from low energies up to = 2 ~TeV.Comment: 28 pages, LaTex, 6 figures, 8 tables, a uuencoded file containing the
latex file and figures is available via anonymous ftp at
ftp://ftp.ifh.de/pub/preprint/desy95-167.uu and the complete ps file also
from http://www.ifh.de/~riemann/desy95-167.ps.g
Predictions for Fermion Pair Production at e+e- Colliders
We discuss the status and some ongoing upgrades of the ZFITTER program for
applications at e+e- colliders LEP1/SLC, LEP2, GigaZ, and TESLA. The inclusion
of top quark pair production is under work.Comment: 10 pages, 1 table, 2 figures, uses npb.sty, to appear in the
proceedings of Zeuthen Workshop: Loops and Legs in Quantum Field Theory, 9-14
April, Bastei, German
J_AW,WA functions in Passarino-Veltman reduction
In this paper we continue to study a special class of Passarino-Veltman
functions J arising at the reduction of infrared divergent box diagrams. We
describe a procedure of separation of two types of singularities, infrared and
mass singularities, which are absorbed in simple C0 functions. The infrared
divergences of C0's can be regularized then by any method: photon mass,
dimensionally or by the width of an unstable particle. Functions J, in turn,
are represented as certain linear combinations of the standard D0 and C0
Passarino-Veltman functions. The former are free of both types of singularities
and are expressed as explicit and compact linear combinations of logarithms and
dilogarithm functions. We present extensive comparisons of numerical results
with those obtained with the aid of the LoopTools package
ZFITTER v.6.21 - A Semi-Analytical Program for Fermion Pair Production in e+e- Annihilation
We describe ZFITTER, a Fortran program based on a semi-analytical approach to
fermion pair production in e+e- annihilation at a wide range of centre-of-mass
energies, including the PETRA, TRISTAN, LEP1/SLC, and LEP2 energies. A flexible
treatment of complete O(alpha) QED corrections and of some higher order
contributions is made possible with three calculational chains containing
different realistic sets of restrictions in the photon phase space. Numerical
integrations are at most one-dimensional. Complete O(alpha) weak loop
corrections supplemented by selected higher-order terms may be included. The
program calculates Delta r, the Z width, differential cross-sections, total
cross-sections, integrated forward-backward asymmetries, left-right
asymmetries, and for tau pair production also final-state polarization effects.
Various interfaces allow fits to be performed with different sets of free
parameters.Comment: 200 pages, Latex2e, 26 figures, 4 tables; uses axodraw, epsfig, epsf,
graphicx, espcrc1; typos of v.1 corrected, version for subm. to Comp. Phys.
Commu
The Character of Z-pole Data Constraints on Standard Model Parameters
Despite the impressive precision of the Z-pole measurements made at LEP and
SLC, the allowed region for the principle Standard Model parameters responsible
for radiative corrections (the mass of the Higgs, the mass of the top and
alpha(Mz)) is still large enough to encompass significant non-linearities. The
nature of the experimental constraints therefore depends in an interesting way
on the "accidental" relationships among the various measurements. In
particular, the fact that the Z-pole measurements favor values of the Higgs
mass excluded by direct searches leads us to examine the effects of external
Higgsstrahlung, a process ignored by the usual precision electroweak
calculations.Comment: 9 pages, 6 figures, REVTeX format; added reference in section IV;
added paragraph on widths and a few cosmetic changes to correspond to
published versio
GENTLE/4fan v.2.0 - A Program for the Semi-Analytic Calculation of Predictions for the Process e+e- -> 4f
We describe version 2.0 of the Fortran program GENTLE/4fan for the
semi-analytic computation of cross-sections and distributions in four-fermion
production in e+e- annihilation. GENTLE/4fan covers all charged current and
neutral current our-fermion final states with no identical particles, no
electrons, and no electron neutrinos in the final state. Initial state
radiation representing the most relevant quantum corrections and anomalous
triple gauge boson couplings have been included.Comment: 38 pages, LaTex, 4 tables, uses fleqn.sty and elsart.cl
HECTOR 1.00 - A program for the calculation of QED, QCD and electroweak corrections to ep and lN deep inelastic neutral and charged current scattering
A description of the Fortran program HECTOR for a variety of semi-analytical
calculations of radiative QED, QCD, and electroweak corrections to the
double-differential cross sections of NC and CC deep inelastic charged lepton
proton (or lepton deuteron) scattering is presented. HECTOR originates from the
substantially improved and extended earlier programs HELIOS and TERAD91. It is
mainly intended for applications at HERA or LEPxLHC, but may be used also for
muon scattering in fixed target experiments. The QED corrections may be
calculated in different sets of variables: leptonic, hadronic, mixed,
Jaquet-Blondel, double angle etc. Besides the leading logarithmic approximation
up to order O(alpha^2), exact order O(alpha) corrections and inclusive soft
photon exponentiation are taken into account. The photoproduction region is
also covered.Comment: 74 pages, LaTex, 14 figures, 7 tables, a uuencoded file containing
the latex file and figures is available from: http://www.ifh.de/theory/ or on
request from e-mail: [email protected]
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