arXiv subjects
Publications and source records attributed to Thorsten Ohl.
I describe the optimizing matrix element generator O'Mega and Wolfgang Kilian's event generator generator WHIZARD. These tools cooperate in the automated production of efficient unweighted event generators for linear collider physics.
I sketch the architecture of O'Mega, a new optimizing compiler for tree amplitudes in quantum field theory. O'Mega generates the most efficient code currently available for scattering amplitudes for many polarized particles in the standard model. A complete infrastructure for physics beyond the standard model is provided.
The interactions of electroweak gauge bosons are severely constrained by the symmetries inferred from low energy observables. The exploration of the dynamics of electroweak symmetry breaking requires therefore both an experimental sensitivity and a theoretical precision that is better than the natural scale of deviations from minimal extrapolations of the low energy effective theory. Some techniques for obtaining improved theoretical predictions for precision tests at a future e^+e^- linear collider are discussed.
We describe the explicit construction of groves, the smallest gauge invariant classes of tree Feynman diagrams in gauge theories
We describe the explicit construction of groves, the smallest gauge invariant classes of tree Feynman diagrams in gauge theories. The construction is valid for gauge theories with any number of group factors which may be mixed. It requires no summation over a complete gauge group multiplet of external matter fields. The method is therefore suitable for defining gauge invariant classes of Feynman diagrams for processes with many observed final state particles in the standard model and its extensions.
We present the results of a complete tree level calculation of the processes pp(\bar p) -> Wb\bar b and Wb\bar b + jet that includes the single top signal and all irreducible backgrounds simultaneously. In order to probe the structure of the Wtb coupling with the highest possible accuracy and to look for possible deviations from standard model predictions, we identify sensitive observables and propose an optimal set of cuts which minimizes the background compared to the signal. At the LHC, the single top and the single anti-top rates are different and the corresponding asymmetry yields additional information. The analysis shows that the sensitivity for anomalous couplings will be improved at the LHC by a factor of 2--3 compared to the expectations for the first measurements at the upgraded Tevatron. Still, the bounds on anomalous couplings obtained at hadron colliders will remain 2--8 times larger than those from high energy gamma-e colliders, which will, however, not be available for some time. All basic calculations have been carried out using the computer package CompHEP. The known NLO corrections to the single top rate have been taken into account.
We present a new adaptive Monte Carlo integration algorithm for ill-behaved integrands with non-factorizable singularities. The algorithm combines Vegas with multi channel sampling and performs significantly better than Vegas for a large class of integrals appearing in physics.
We present a general classification of all four fermion final states in $γγ$~collisions and a calculation of cross sections below the $W^+W^-$-threshold.
We propose a general classification of all four fermion final states in $γγ$ collisions at a future $e^+e^-$ Linear Collider and discuss the relation of ``signal'' and ``background'' contributions in vector boson production. We utilize the results in a critical examination of the Higgs signal in sub-threshold $W^+W^-$ pair production.
We present a calculation of the renormalized heavy-light and heavy-heavy currents in HQET at order O(1/m_Q^2).
I discuss the state of the art and outline direction for research in event generation for electroweak physics at LEP2 and e+e- Linear Colliders.
I describe parameterizations of realistic $e^\pm$- and $γ$-beam spectra at future linear $e^+e^-$-colliders. Emphasis is put on simplicity and reproducibility of the parameterizations, supporting reproducible physics simulations. The parameterizations are implemented in a library of distribution functions and event generators.
We describe the new version of the Monte Carlo event generator WOPPER for four fermion production through W-pairs including resummed leading logarithmic QED radiative corrections. Among the new features included are singly resonant background diagrams and anomalous triple gauge boson couplings.
We present a new calculation of the renormalized HQET Lagrangian at order O(1/m_Q^2) and discuss the consequences of the BRST invariance of QCD and the reparameterization invariance of HQET. Our result corrects earlier, conflicting calculations and sets the stage for the calculation of the renormalized currents at order O(1/m_Q^2).
Feynmf is a LaTeX package for easy drawing of professional quality Feynman diagrams with Metafont (or Metapost). Feynmf lays out most diagrams satisfactorily from the structure of the graph without any need for manual intervention. Nevertheless all the power of Metafont (or Metapost) is available for the most complicated cases.
We describe the Monte Carlo event generator WOPPER for four fermion production through W-pairs including resummed leading logarithmic QED radiative corrections.
This manual describes version 1.6 of the programming language hepawk, designed for convenient scanning of data structures arising in the simulation of high energy physics events. The interpreter for this language has been implemented in FORTRAN77, therefore hepawk runs on any machine with a FORTRAN77 compiler.
We report on the status of the Monte Carlo event generator WOPPER. Version 1.1 of WOPPER describes four fermion production at LEP-II and beyond with leading logarithmic radiative corrections in the double W pole approximation. These approximations are appropriate for almost all practical purposes, but the inclusion of these finite width effects and radiative corrections is nevertheless indispensable for LEP-II physics.