arXiv subjects
Publications and source records attributed to W. Hollik.
We study the associated production of charged Higgs bosons with $W$ gauge bosons in high energy $e^+ e^-$ collisions at the one loop level. We present the analytical results and give a detailed discussion for the total cross section predicted in the context of a general Two Higgs Doublet Model (THDM).
We analyze the impact of the recent Feynman-diagrammatic (FD) two-loop results for the mass of the lightest CP-even Higgs boson in the MSSM on the theoretical upper bound for mh as a function of tan(beta). The results are compared with previous results obtained by renormalization group (RG) methods. The incorporation of dominant FD two-loop corrections into the decay width Γ(h -> f \bar f) is also discussed.
We review the comparison of the results for the neutral CP-even Higgs-boson masses recently obtained within the Feynman-diagrammatic approach with the previous results based on the renormalization group approach. We show that the results differ by new genuine two-loop contributions present in the Feynman-diagrammatic calculation. The numerical effect of these terms on the result for m_h is briefly discussed.
For supersymmetric gauge theories a consistent regularization scheme that preserves supersymmetry and gauge invariance is not known. In this article we tackle this problem for supersymmetric QED within the framework of algebraic renormalization. For practical calculations, a non-invariant regularization scheme may be used together with counterterms from all power-counting renormalizable interactions. From the Slavnov--Taylor identity, expressing gauge invariance, supersymmetry and translational invariance, simple symmetry conditions are derived that are important in a twofold respect: they establish exact relations between physical quantities that are valid to all orders, and they provide a powerful tool for the practical determination of the counterterms. We perform concrete one-loop calculations in dimensional regularization, where supersymmetry is spoiled at the regularized level, and show how the counterterms necessary to restore supersymmetry can be read off easily. In addition, a specific example is given how the supersymmetry transformations in one-loop order are modified by non-local terms.
The masses of the neutral CP-even Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) are predicted on the basis of explicit Feynman-diagrammatic calculations. The results, containing the complete diagrammatic one-loop corrections, the leading two-loop corrections of O(alpha alpha_s) and further improvements taking into account leading electroweak two-loop and higher-order QCD contributions, are discussed and compared with results obtained by renormalization group calculations. Good agreement is found in the case of vanishing mixing in the scalar top sector, while sizable deviations occur if scalar top mixing is taken into account. By means of a Taylor expansion a compact approximation formula for the mass of the lightest Higgs boson, m_h, is derived. The quality of the approximation in comparison with the full result is analyzed.
A compact approximation formula for the mass of the lightest neutral CP-even Higgs boson, m_h, in the Minimal Supersymmetric Standard Model (MSSM) is derived from the diagrammatic two-loop result for m_h up to O(alpha alpha_s). By analytically expanding the diagrammatic result the leading logarithmic and non-logarithmic as well as the dominant subleading contributions are obtained. The approximation formula is valid for general mixing in the scalar top sector and arbitrary choices of the parameters in the Higgs sector of the model. Its quality is analyzed by comparing it with the full diagrammatic result. We find agreement with the full result better than 2 GeV for most parts of the MSSM parameter space.
Radiative one-loop corrections to fermion pair production in $e^+e^-$ annihilation are calculated in the Minimal Supersymmetric Standard Model (MSSM). The size of the non-standard corrections is discussed for the process e^+e^- to mu^+mu^- and e^+e^- to hadrons at LEP2 energies and for e^+e^- to t tbar at a high energy e^+e^- collider. The relative difference between the predictions of the MSSM and the Standard Model is typically below 10%.
We present detailed results of a diagrammatic calculation of the leading two-loop QCD corrections to the masses of the neutral CP-even Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM). The two-loop corrections are incorporated into the full diagrammatic one-loop result and supplemented with refinement terms that take into account leading electroweak two-loop and higher-order QCD contributions. The dependence of the results for the Higgs-boson masses on the various MSSM parameters is analyzed in detail, with a particular focus on the part of the parameter space accessible at LEP2 and the upgraded Tevatron. For the mass of the lightest Higgs boson, m_h, a parameter scan has been performed, yielding an upper limit on m_h which depends only on tan(beta). The results for the Higgs-boson masses are compared with results obtained by renormalization group methods. Good agreement is found in the case of vanishing mixing in the scalar quark sector, while sizable deviations occur if squark mixing is taken into account.
In this conference report a summary is given on the theoretical work that has contributed to provide accurate theoretical predictions for testing the standard model in present and future experiments. Precision calculations for the vector boson masses, for the Z resonance, W pair production, and for the g-2 of the muon are reviewed and the theoretical situation for the Higgs sector is summarized. The status of the standard model is discussed in the light of the recent high and low energy data. New Physics beyond the standard model is briefly addressed as well, with special emphasis on the minimal supersymmetric standard model. A few references have been added.
FeynHiggs is a Fortran code for the calculation of the masses of the neutral CP-even Higgs bosons in the MSSM up to two-loop order. It is based on the complete diagrammatic on-shell results at the one-loop level, the leading diagrammatic two-loop QCD contributions and further improvements taking into account leading electroweak two-loop and leading higher-order QCD corrections. The Higgs-boson masses are calculated as functions of the MSSM parameters for general mixing in the scalar top sector and arbitrary choices of the parameters in the Higgs sector of the model.
The leading diagrammatic two-loop corrections are incorporated into the prediction for the mass of the lightest Higgs boson, $\mh$, in the Minimal Supersymmetric Standard Model (MSSM). The results, containing the complete diagrammatic one-loop corrections, the new two-loop result and refinement terms incorporating leading electroweak two-loop and higher-order QCD contributions, are discussed and compared with results obtained by renormalization group calculations. Good agreement is found in the case of vanishing mixing in the scalar quark sector, while sizable deviations occur if squark mixing is taken into account.
We perform a diagrammatic calculation of the leading two-loop QCD corrections to the masses of the neutral CP-even Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM). The results are valid for arbitrary values of the parameters of the Higgs and scalar top sector of the MSSM. The two-loop corrections are found to reduce the mass of the lightest Higgs boson considerably compared to its one-loop value. The numerical results are analyzed in the GUT favored regions of small and large \tan β. Their impact on a precise prediction for the mass of the lightest Higgs boson is briefly discussed.
Diagrammatic two-loop results are presented for the leading QCD corrections to the masses of the neutral CP-even Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM). The results are valid for arbitrary values of the parameters of the Higgs and scalar top sector of the MSSM. Their impact on a precise prediction for the mass of the lightest Higgs boson is briefly discussed.
A minimal supersymmetric version of the Standard Model with complex parameters allows contributions to the weak-electric dipole moments of fermions at the one-loop level. Assuming generation-diagonal trilinear soft-susy-breaking terms and the usual GUT constraint, a set of CP-violating physical phases can be introduced. In this paper the general expressions for the one-loop contribution to the WEDM in a generic renormalizable theory are given and the size of the WEDM of the tau lepton and the b quark in such a supersymmetric model is discussed.
The calculation of electroweak precision observables in the MSSM is reviewed. The description of the 1997 data and the results of updated global fits are discussed in comparison with the Standard Model.
This talk summarizes topical theoretical work for tests of the electroweak theory and reviews the status of the electroweak Standard Model in view of the recent precision data reported at the 1997 summer conferences.
We calculate the MSSM $O(α)$ corrections to the main production processes of strong top pair production at the upgraded Tevatron and at the LHC. In exploring the potential of future hadron colliders for performing electroweak precision physics we study their effects on the total hadronic cross sections, the invariant $t\bar t$ mass distributions and give first results for parity violating asymmetries in the production of left and right handed top quarks.
In the supersymmetric extension of the Standard Model we derive the two-loop QCD corrections to the scalar quark contributions to the electroweak precision observables entering via the rho parameter. A very compact expression is derived for the gluon-exchange contribution. The complete analytic result for the gluino-exchange contribution is very lengthy; we give expressions for several limiting cases that were derived from the general result. The two-loop corrections, generally of the order of 10 to 30% of the one-loop contributions, canbe very significant. Contrary to the Standard Model case, where the QCD corrections are negative and screen the one-loop value, the corresponding corrections in the supersymmetric case are in general positive, therefore increasing the sensitivity in the search for scalar quarks through their virtual effects in high-precision electroweak observables.