Yukawa-coupling corrections to scalar quark decays

Heavy squark decays into top and charginos or neutralinos could be an unexpected source of top quarks at hadron colliders. A detailed treatment of these processes is necessary for a reliable calculation of both the top quark production cross-section and the standard top quark branching ratio in the MSSM. Along this line we compute the electroweak corrections to the sbottom decays sbottom_a --> chargino_i top within the Yukawa coupling approximation. The calculation of these higher order contributions requires renormalization of both the bottom squark mixing angle and of tan(beta). This type of corrections gives the leading order electroweak effects at low and high tan(beta).Comment: 16 pages, LaTeX, 5 figures included using epsfig. Comments added, equation 25 corrected, labels of fig.2 corrected, references update

Top quark decay into charged Higgs boson in a general Two-Higgs-Doublet model: implications for the TEVATRON data

We analyze the unconventional top quark decay mode t -> H^+ b at the quantum level within the context of general Two-Higgs-Doublet models by including the full electroweak effects from the Yukawa couplings. The results are presented in the on-shell renormalization scheme with a physically well motivated definition of tan(beta). While the QCD corrections have been taken into account in the current experimental analyses of that decay, the electroweak effects have always been neglected. However, we find that they can be rather large and could dramatically alter the interpretation of the present data from the Tevatron collider. For instance, in large portions of the parameter space the electroweak effects prevent the Tevatron data from placing any bound at all to the charged Higgs mass for essentially any value of tan(beta).Comment: 11 pages, LaTeX, 4 figs included using epsfi

Radiative Corrections to scalar quark decays in the MSSM

We review the one-loop corrections to the partial decay width of sbottom-quark into a top quark and a chargino for the parameter space relevant to the TESLA e+e- linear collider. We present the results available in the literature for the QCD and the Yukawa coupling corrections in a unified framework. In this way a direct comparison of the size of the various corrections is possible.Comment: LaTeX, 11 pages, 7 figures included. Talk presented at the 2nd ECFA/DESY Study on Physics and Detectors for a Linear Electron-Positron Collider. References adde

Radiative corrections to pair production of charged Higgs bosons at TESLA

Charged Higgs particles are a common feature of many extensions of the Standard Model. While its existence with masses up to the TeV scale can be probed at the Tevatron Run II and LHC hadron colliders, a precise determination of its properties would have to wait for a high energy e+e- linear collider. We have computed the complete one-loop electroweak corrections to the cross-section for charged Higgs bosons pair production in e+e- collisions, in the framework of general Two Higgs Doublet Models, as well as the Minimal Supersymmetric Standard Model. A study is presented for typical values of the model parameters, showing the general behaviour of the corrections.Comment: LaTeX, 14 pages, 6 figures included. Talk presented at the 2nd ECFA/DESY Study on Physics and Detectors for a Linear Electron-Positron Collider, Obernai (France) 16-19th October, 199