H. König

Flavor-changing top quark decay within the minimal supersymmetric standard model

We present the results of the gluino and scalar quark contribution to the flavor-changing top quark decay into a charm quark and a photon, gluon, or a {ital Z}{sup 0} boson within the minimal supersymmetric standard model. We include the mixing of the scalar partners of the left- and right-handed top quark. This mixing has several effects, the most important of which is to greatly enhance the {ital c} {ital Z} decay mode for large values of the soft SUSY-breaking scalar mass {ital m}{sub {ital S}} and to give rise to a GIM-like suppressions in the {ital c} {gamma} mode for certain combinations of parameters.

Bounds on second generation scalar leptoquarks from the anomalous magnetic moment of the muon.

We calculate the contribution of second generation scalar leptoquarks to the anomalous magnetic moment of the muon. The coupling {lambda}{sub {phi}}{sub {ital L}} between the leptoquarks, the quarks, and the leptons is taken to be of the order of the electroweak coupling {ital g}{sub 2}. In the near future, the E-821 Collaboration at Brookhaven will reduce the experimental error on this parameter to {delta}{ital a}{sub {mu}}{sup e}{sup x}{sup p}{sup t}{much_gt}4{times}10{sup -}{sup 1}{sup 0}, an improvement of 20 over its current value. Combining this error with the current uncertainty on the hadronic contribution to {ital g}-2 we obtain a bound of {ital m}{sub {phi}}{sub {ital L}}{much_lt}88 GeV for the second generation scalar leptoquark while we get {ital m}{sub {phi}}{sub {ital L}}{much_lt}186 GeV when neglecting the hadronic uncertainty. {copyright} {ital 1995 The American Physical Society.}

\(\mu\rightarrow e\gamma\) decay in the left-right supersymmetric model

Abstract. We calculate the dipole amplitude for the decay

Contribution of scalar loops to the three-photon decay of the Z

\mu\rightarrow e\gamma

Neutralino contribution to the mass difference of\(B_d^0 - \bar B_d^0 \)

and related processes in the left-right supersymmetric model when parity breaking occurs at a considerably large scale. The low-energy flavor violation in the model originates either from the nonvanishing remnants of the left-right symmetry in the slepton mass matrix or from the direct flavor changing lepton-slepton-neutralino interaction. The result is found to be large and already accessible with current experimental accuracy for supersymmetric masses not far above the electroweak scale. It also provides nontrivial constraints on the lepton mixing in the model.

The decayH20 →gg within the Minimal Supersymmetric Standard Model

I corrected 3 mistakes from the first version: that were an omitted Feynman integration in the function f^3_{ij}, a factor of 2 in front of log f^3_{ij} in eq.2 and an overall factor of 2 in Fig.1 c). The final result is changed drastically. Doing an expansion in the Higgs mass I show that the matrix element is identically 0 in the order (MZ/MH)^2, which is due to gauge invariance. Left with an amplitude of the order (MZ/MH)^4 the final result is that the scalar contribution to this decay rate is several orders of magnitude smaller than those of the W boson and fermions.

Gluino and neutralino contribution to the direct CP violation parameter έ

We present a detailed and complete calculation of the neutralino contribution to the mass difference ΔmBd0/mBd0 within the MSSM. We include the complete mixing matrices of the neutralinos and of the scalar partners of the left and right handed bottom quark. We find that the neutralino contribution is generally small but can be of the same order of the chargino contribution and much larger than that of the gluino over a small range ofmS, givenmg2 andμ and for tanβ∼50.

Reanalysis of the mass difference of\(B_d^0 - \bar B_d^0 \) within the Minimal Supersymmetric Standard Modelwithin the Minimal Supersymmetric Standard Model

I present a detailed SUSY QCD calculation of the decay rate of the lightest Higgs bosonH20 into two gluons, where all quarks and scalar quarks are taken within the relevant loop diagrams. I include the mixing of all the scalar partners of the left and right handed quarks and show that their contribution is more than several tens of per cent compared to the quark contribution in the MSSM for some SUSY parameter space. Furthermore the MSSM fermionic contribution is enhanced by several factors for large tanβ and large Higgs masses. As a result, the two gluon decay rate ofH20 is much larger than the two gluon decay rate of an equal mass standard model Higgs boson. I further compare the decay mode ofH20→gg to the similar decay modes ofH20→cc andH20→bb including one loop QCD corrections and show that in some casesΓ(H20→gg) is even higher thanΓ(H20→cc), although still much smaller thanΓ(H20→bb).

Charged heavy lepton production in superstring-inspired E{sub 6} models

I present a detailed and complete calculation of the gluino and neutralino contribution to the direct CP violating parameter έ within the MSSM. I include the complete mixing matrices of the neutralino and of the scalar partners of the left and right handed down quarks. I find that the neutralino contribution is generally small but can be larger than the gluino contribution for small values ms ≤ 400 GeV of the supersymmetric breaking scale.

K +→π + vv andK L 0 →μ + μ − decays within the Minimal Supersymmetric Standard Model

AbstractWe present a detailed and complete calculation of the loop corrections to the mass difference