Strong Interaction Effects in Stop Pair Production at $e^+ e^-$ Colliders

TL;DR

This paper analyzes strong interaction effects in stop squark pair production at $e^+ e^-$ colliders, exploring perturbative and non-perturbative phenomena, and proposes methods to detect stops even with small mass differences.

Contribution

It introduces a detailed study of strong interaction effects, including non-perturbative fragmentation, in stop pair production at $e^+ e^-$ colliders, with numerical results for current and future experiments.

Findings

Hard gluon events help detect stops with small mass splitting.

Events can establish the triplet nature of $ ilde{t}_1$ under $SU(3)_C$.

Non-perturbative fragmentation modeling has significant ambiguities.

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 stop pair 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 $SU(3)_C$. 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 $\sqrt{s}=500$ GeV.