We h a v e determined the theoretical predictions for the cross-sections of squark and gluino production at p p and pp colliders (Tevatron and LHC) in next-to-leading order of supersymmetric QCD. By reducing the dependence on the renormalization/factorization scale considerably, the theoretically predicted values for the cross-sections are much more stable if these higher-order corrections are implemented. If squarks and gluinos are discovered, this improved stability translates into a reduced error on the masses, as extracted experimentally from the size of the production cross-sections. The cross-sections increase signicantly if the next-to-leading order corrections are included at a renormalization/factorization scale near the average mass of the produced massive particles. This rise results in improved lower bounds on squark and gluino masses. By contrast, the shape of the transverse-momentum and rapidity distributions remains nearly unchanged when the next-to-leading order corrections are included.Research supported by a fellowship of the Royal Dutch Academy of Arts and Sciences.

We have determined the QCD corrections to the production of squark-antisquark pairs in pp 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.

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 qqg 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. ‡ present address §

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.Comment: 20 pages, LaTeX, 8 figures (uses epsfig). Complete postscript file available at http://rulgm4.LeidenUniv.nl/preprints.htm