arXiv subjects
Publications and source records attributed to R. Höpker.
The partial widths are determined for stop decays to top quarks and gluinos, and gluino decays to stop particles and top quarks (depending on the masses of the particles involved). The widths are calculated including one-loop SUSY-QCD corrections. The radiative corrections for these strong-interaction decays are compared with the SUSY-QCD corrections for electroweak stop decays to quarks and neutralinos/charginos and top-quark decays to stops and neutralinos.
We present the cross-sections for the hadroproduction of squarks and gluinos in next-to-leading order of supersymmetric QCD. The four possible final states squark-antisquark, squark-squark, gluino-gluino and squark-gluino are analysed for the hadron colliders Tevatron and LHC. The dependence of the cross-sections on the renormalization and factorization scale is reduced significantly. The shape of the transverse-momentum and rapidity distributions remains nearly unchanged when the next-to-leading order SUSY-QCD contributions are included. The size of the corrections at the central scale, given by the average mass of the produced particles, varies between $+5\%$ and $+90\%$.
A status report is given of the calculations of next-to-leading-order ($N=1$) supersymmetric QCD corrections to the production of squarks and gluinos in $p\bar{p}/pp$ collisions. The implementation of these SUSY-QCD corrections leads to more stable theoretical predictions and to a substantial increase of the production cross-sections. In addition we give a discussion of the use of the $\overline{MS}$ scheme for renormalizing the coupling constants in the QCD sector of ($N=1$) supersymmetric theories.
The partial widths are determined for squark decays to gluinos and quarks, and gluino decays to squarks and quarks, respectively. The widths are calculated including one-loop SUSY-QCD corrections. The corrections amount to $+$30\% to $+$50\% for squark decays and $-$10\% to $+$10\% for gluino decays. We have derived the results in the \DR ~and \MS ~renormalization schemes, and we have demonstrated explicitly that the one-loop effective $qqg$ and $q\sq\gl$ couplings are equal in the limit of exact supersymmetry.
The next-to-leading order QCD corrections to the production of gluino pairs at the Tevatron are presented in this paper. Similar to the production of squark-antisquark pairs, the dependence of the cross section on the renormalization/factorization scale is reduced considerably by including the higher-order corrections. The cross section increases with respect to the lowest-order calculation which, in previous experimental analyses, had been evaluated at the scale of the invariant energy of the partonic subprocesses.
We present the distributions for gluon radiation off stop-antistop particles produced in $e^+e^-$ annihilation: $e^+e^- \to \tilde t \bar{\tilde t} g$. For high energies the splitting functions of the fragmentation processes $\tilde t \to \tilde t g$ and $g \to \tilde t \bar{\tilde t}$ are derived; they are universal and apply also to high-energy stop particles produced at hadron colliders.
We have determined the QCD corrections to the production of squark-antisquark pairs in $p\bar p$ collisions at the Tevatron. If the next-to-leading order corrections are taken into account, the renormalization/factorization scale dependence of the theoretical prediction for the cross section is reduced considerably. The higher order corrections increase the production cross section at the Tevatron by about a factor two if we compare the next-to-leading order prediction at a scale near the squark mass with the lowest order prediction for which, in the experimental analyses, the scale was identified with the invariant energy of the parton subprocess. This results in a rise of the experimental lower bound on the squark mass from the Tevatron by about $20$ GeV.