Searcharxiv⌕ Search

arXiv subjects

A. Leike

Publications and source records attributed to A. Leike.

At least 19 recordsLinked to original sources
arXiv2003

Elektroweak one-loop corrections for e^+e^- annihilation into t\bar{t} including hard bremsstrahlung

We present the complete electroweak one-loop corrections to top-pair production at a linear e^+e^- collider in the continuum region. Besides weak and photonic virtual corrections, real hard bremsstrahlung with simple realistic kinematical cuts is included. For the bremsstrahlung we advocate a semi-analytical approach with a high numerical accuracy. The virtual corrections are parametrized through six independent form factors, suitable for Monte-Carlo implementation. Alternatively, our numerical package topfit, a stand-alone code, can be utilized for the calculation of both differential and integrated cross sections as well as forward--backward asymmetries.

hep-ph↗
arXiv2002

Status of Electroweak Corrections to Top Pair Production

We review the status of electroweak radiative corrections to top-pair production at a Linear Collider well above the production threshold. We describe the Fortran package topfit and present numerical results at sqrt(s) = 500 GeV, 1 TeV, and 3 TeV.

hep-ph↗
arXiv2002

One-loop corrections to the process e+ e- -> t tbar including hard bremsstrahlung

Radiative corrections to the process e+ e- to t tbar are calculated in one-loop approximation of the Standard Model. There exist results from several groups. This talk provides further comparisons of the complete elektroweak contributions, including hard bremsstrahlung. The excellent final agreement of the different groups allows to continue by working on a code for an event generator for TESLA and an extension to e+ e- to 6 fermions.

hep-ph↗
arXiv2000

Discovery and Identification of W' Bosons at e+e- Colliders

We report on studies of the sensitivity to extra gauge bosons of the reactions e^+ e^- -> nu nubar gamma and e gamma -> nu q + X to extract discovery limits for W' 's. The discovery potential for a W' is, for some models, comparable to that of the LHC. These processes may be also useful for determining W' and Z' couplings to fermions which would complement measurements made at the Large Hadron Collider.

hep-ph↗
arXiv2000

Two-Fermion Production in Electron-Positron Collisions

This report summarizes the results of the two-fermion working group of the LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the theoretical calculations of the two fermion production process in the electron-positron collision at LEP2 center of the mass energies are reported. The Bhabha process and the production of muon, tau, neutrino and quark pairs is covered. On the basis of comparison of various calculations, theoretical uncertainties are estimated and compared with those needed for the final LEP2 data analysis. The subjects for the further studies are identified.

hep-ph↗
arXiv1998

Radiative Corrections to Deep Inelastic Scattering in the Presence of an Additional Z' at LEP x LHC

The study of ep-scattering at LEP x LHC offers an interesting opportunity to search for additional heavy neutral gauge bosons. We study the influence of radiative corrections, especially of the potentially large QED contributions, to the expected cross sections. These corrections are typically of the same order as the effect searched for or even larger and have to be taken into account properly.

hep-ph↗
arXiv1998

ZZ' Mixing in Presence of Standard Weak Loop Corrections

We derive a method for a common treatment of Z' exchange, QED corrections, and weak loops. It is based on the form factor approach to the description of weak loop corrections to partial Z widths and cross sections. Problems connected with ZZ' mixing are discussed with special care. Our theoretical results are applied to the package ZFITTER. We demonstrate two different ways to the data analysis - one based on an extension of the standard model cross sections, the other on model-independent formulae together with the Z width calculations in presence of a Z'. With the resulting package ZEFIT+ZFITTER, LEP1 data from fermion pair production, including Bhabha scattering, can be analysed on, but also off the Z peak. Further, the code may be used at very high energies, e.g. in the region of a possible future linear e+e- collider.

hep-ph↗
arXiv1998

The Phenomenology of Extra Neutral Gauge Bosons

The phenomenological constraints on extra neutral gauge bosons at present and at future colliders are reviewed. Special attention is paid to the influence of radiative corrections, systematic errors, and kinematic cuts on the Z' constraints. Simple estimates of the Z' constraints from different reactions are derived. They make the physical origin of these constraints transparent. The results existing in the literature are summarized and compared with the estimates. The consequence of model assumptions on the Z' constraints is discussed. The paper starts with an overview of Z' parameters and the possible links between them by model assumptions. It continues with a discussion of Z' limits and Z' measurements in different reactions at e+e- and mu+mu- colliders. It follows an overview of the corresponding limits at proton colliders. Possible Z' constraints from other reactions as ep collisions, atomic parity violation, neutrino scattering and cosmology are briefly mentioned.

hep-ph↗
arXiv1998

The Bremsstrahlung Process Nu_Tau -> Nu_e E+ E- Gamma

The bremsstrahlung process Nu_Tau -> Nu_e E+ E- Gamma is the dominant photon-producing decay of heavy Tau neutrinos with m_Nu_Tau > 2 m_e so that this process is instrumental for supernova 1987A constraints on the properties of these particles, notably on their mixing amplitude with Nu_e. We calculate the rate of the bremsstrahlung process as well as the photon spectrum and the angular distribution relative to the spin direction of the parent neutrino. We carefully pay attention to the difference between Dirac and Majorana neutrinos.

hep-ph↗
arXiv1997

Form factors and radiative Corrections in Z' Physics

This lecture contains a pedagogical approach to the description of Z' physics in the formalism of form factors. Usually, only electroweak corrections are described by form factors, which modify the Weinberg angle and the overall normalization. It is demonstrated how this formalism can be extended to include different Born contributions. In the second part of the lecture, QCD and QED corrections are considered. The development and consequences of the radiative tail for a Z' search are discussed in detail.

hep-ph↗
arXiv1997

Event Generators for WW Physics

The report summarizes the results of the activities of the Working Group on Event Generators for WW Physics at CERN during 1995.

hep-ph↗
arXiv1997

Radiation of two hard gluons in e+e- ---> q (bar)q

The process e+e- ---> q(bar) q g g where all final particles are hard is treated in a semi-analytic approach. Cuts on the invariant masses of the quark and the gluon pair can be applied. The total cross section is obtained by three numerical integrations.

hep-ph↗
arXiv1997

Remark on Z' limits at hadron colliders

Simple estimates for Z' exclusion limits and Z' model measurements in pp (p bar p) collisions are derived. Due to properties of the structure functions, the Z' exclusion limits depend only logarithmically on the Z' couplings to fermions and on the integrated luminosity. The predicted scaling of Z' exclusion limits and errors of Z' measurements with the c.m. energy and luminosity allows an easy extrapolation of existing analyses to other colliders.

hep-ph↗
arXiv1996

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.

hep-ph↗
arXiv1996

Model-Independent Z' Constraints from Measurements at the Z Peak

Model independent constraints on extra neutral gauge bosons are obtained from partial decay widths of the Z_1 and forward-backward and left-right asymmetries at the Z_1 peak. Constraints on the ZZ' mixing angle in E_6 models are considered as special cases.

hep-ph↗