arXiv subjects
Publications and source records attributed to A. Bartl.
We calculate the supersymmetric ${\cal O}(α_s)$ QCD corrections to stop and sbottom decays into vector bosons within the Minimal Supersymmetric Standard Model. We give analytic formulae and perform a numerical analysis of these decays. We find that SUSY-QCD corrections to the decay widths are typically -5% to -10% depending on the squark masses, squark mixing angles, and the gluino mass.
We present a detailed study of the decays of the Higgs bosons $H^+$, $H^0$, and $A^0$ within the Minimal Supersymmetric Standard Model including SUSY--QCD corrections. We find that the supersymmetric modes $\tilde t \bar{\tilde b}$ ($\tilde t \bar{\tilde t}$, and for large $\tanβ$ $\tilde b \bar{\tilde b}$) can dominate the $H^+$ ($H^0$, $A^0$) decays in a wide range of the model parameters due to the large Yukawa couplings and mixings of $\tilde t$ and $\tilde b$. Compared to the conventional modes $H^+ \to τ^+ ν_τ, t \bar b$, and $H^0, A^0 \to t \bar t, b \bar b$, the supersymmetric modes can have an important impact on the Higgs boson searches at future colliders.
We present numerical predictions for the decay branching ratios of the heavier stop and sbottom mass eigenstates. We estimate the precision to be expected for the determination of the underlying supersymmetry parameters of the stop and sbottom systems.
We calculate the supersymmetric QCD corrections in order $α_s$ to the the widths of the Higgs boson decays $H^+ \to \st \bar\sb$ and $H^0, A^0 \to \st \bar\st, \sb \bar\sb$ in the on--shell scheme within the Minimal Supersymmetric Standard Model. We find that the QCD corrections are significant, but that the squark pair decay modes are still dominant in a wide parameter region.
We discuss pair production and decays of stops, sbottoms, $τ$-sneutrinos, and staus in $e^+e^-$ annihilation in the energy range $\sqrt{s} = 500 GeV$ to 2 TeV. Numerical predictions within the Minimal Supersymmetric Standard Model (MSSM) for cross sections and decay rates are presented. We study the stop discovery potential for $\sqrt{s} = 500 GeV$ and $10 \fb^{-1}$ integrated luminosity for polarized e^- beams. Moreover, we give an estimate of the error of the soft-breaking stop and sbottom parameters that can be obtained by cross section measurements with polarized e^- beams.
We study the pattern of gluino cascade decays in a class of supersymmetric models where R-parity is spontaneously broken. We give a detailed discussion of the R-parity violating decays of the lightest neutralino, the second lightest neutralino and the lightest chargino. The multi-lepton and same-sign dilepton signal rates expected in these models are compared with those predicted in the Minimal Supersymmetric Standard Model. We show that these rates can be substantially enhanced in broken R-parity models.
We calculate the supersymmetric QCD corrections in order $α_s$ to the cross section $e^+ e^- \to \sq_i \bar\sq_j$ $(i,j = 1, 2)$ within the Minimal Supersymmetric Standard Model. We pay particular attention to the case of the left--right squark mixing and to the renormalization of the mixing angle. The corrections due to gluino exchange turn out to be smaller than those due to gluon exchange, but they can be significant at higher energies even for a gluino mass of a few hundred GeV.
We calculate the supersymmetric QCD corrections in order $α_s$ to the decays $\squark_i \to q' \chargino_j$ (i,j = 1,2) and $\squark_i \to q \neutralino_k$ (k = 1,...4) within the Minimal Supersymmetric Standard Model. In particular we consider the decays of squarks of the third generation, $\stop_i$ and $\sbottom_i$ (i = 1,2), where the left--right mixing must be taken into account. The corrections turn out to be of about 10\%, except for higgsino--like charginos or neutralinos, where they can go up to 40\%.
In a class of supersymmetric models with R-parity breaking the lightest stop can have new decay modes into third generation fermions, $\tilde{t}_1 \rightarrow b + τ$. We show that this decay may be dominant or at least comparable to the ordinary R-parity conserving mode $\tilde{t}_1 \rightarrow c + \tildeχ_1^0$, where $\tildeχ_1^0$ denotes the lightest neutralino. The new R-parity violating decay mode could provide new signatures for stop production at LEP.
We discuss pair production and decays of stops, sbottoms, and staus in $e^+e^-$ annihilation in the energy range $\sqrt{s}$ = 500 GeV to 2 TeV. We present numerical predictions within the Minimal Supersymmetric Standard Model for cross sections and decay rates. We study the stop discovery potential for $\sqrt{s}$ = 500 GeV and $10~\fb^{-1}$ integrated luminosity with full statistics background simulation.
We present a comprehensive study of pair production and decay of stops, sbottoms, and staus in $e^+ e^-$ annihilation at LEP2. We give numerical predictions within the Minimal Supersymmetric Standard Model for cross sections and decay rates, and discuss the important signatures. In the case of stau production we also study the polarization of the tau in the decays stau_1 -> tau + neutralino_{1,2}.
Review of prospects for discovery of new physics signals at LEP2. The areas covered include SUSY, exotic fermions, BESS models, leptoquarks, virtual effects and CP violating observables.
We present a complete calculation of the QCD corrections (of the order $α_s$) to the width of the decay $H^+ \to t \bar{b}$ within the Minimal Supersymmetric Standard Model. We find that the QCD corrections are quite important, and that the supersymmetric QCD corrections (due to gluino, stop and sbottom exchange) can be comparable to or even larger than the standard QCD corrections in a large region of the supersymmetric parameter space. This is mainly due to the effect of large left-right mixings of stop and sbottom. This could significantly affect the phenomenology of the $H^+$ search.
We calculate the supersymmetric ${\cal O}(α_s)$ QCD corrections to the width of the decay $H^+ \rightarrow \st\bar{\sb}$ within the Minimal Supersymmetric Standard Model. We find that the QCD corrections are significant, but that they do not invalidate our previous conclusionat tree-level on the dominance of the $\st\bar{\sb}$ mode in a wide parameter region.
We obtain analytic formulae for the cross section of the sequential processes of $e^+ e^- \to t \bar t$ and $t \to b l ν$ in the laboratory frame where the dependence on triple product correlations of the type ($\hat(q}_1 x \hat{q}_2 . \hat{q}_3$), induced by CP violation both in the production and the decay are explicitely shown. Different observables sensitive to CP violation are defined and calculated in the Minimal Supersymmetric Standard Model (MSSM). The observables sensitive to CP violation are of the order of $10^-3$. The dependence on the masses of the supersymmetric particles is also shown.
We summarize the current status and future prospects for low energy (weak scale) supersymmetry. In particular, we evaluate the capabilities of various $e^+e^-$, $p\bar p$ and $pp$ colliders to discover evidence for supersymmetric particles. Furthermore, assuming supersymmetry is discovered, we discuss capabilities of future facilities to dis-entangle the anticipated spectrum of super-particles, and, via precision measurements, to test mass and coupling parameters for comparison with various theoretical expectations. We comment upon the complementarity of proposed hadron and $e^+e^-$ machines for a comprehensive study of low energy supersymmetry.
We analyze the experimental data from the search for new particles at LEP 100 and obtain mass bounds for the neutralinos of the Next--To--Minimal Supersymmetric Standard Model (NMSSM). We find that for $\tanβ\gsim 5.5$ a massless neutralino is still possible, while the lower mass bound for the second lightest neutralino corresponds approximately to that for the lightest neutralino in the Minimal Supersymmetric Standard Model (MSSM).