Strong-interaction effects in stop pair production at $e^+ e^-$ colliders

Abstract

We discuss perturbative and non-perturbative strong-interaction effects in the pair production of stop squarks (\(\tilde t_1\)) at \(e^+e^-\) colliders. Events with an additional hard gluon allow to detect or exclude \(\tilde t_1 \tilde t_1^*\) production even in scenarios with very small mass splitting between \(\tilde t_1\) and an invisible lightest supersymmetric particle (LSP). Such events can also help to establish that \(\tilde t_1\) transforms as a triplet under SU(3)\(_{\mathrm{C}}\). We also carefully study non-perturbative \(\tilde t_1\) fragmentation, which is currently not well understood: not only is the \(\tilde t_1\) fragmentation function not known very well, but also there are ambiguities in the algorithm employed to model fragmentation. We present numerical results both for CERN LEP–183 and for a proposed future \(e^+e^-\) collider operating at center-of-mass energy \(s^{1/2}=500\) GeV.