Renormalization Group Analysis of Supersymmetric Particle Interactions

TL;DR

This paper reanalyzes the RGEs of the MSSM including 1-loop thresholds, revealing effects on coupling splitting, gaugino mass unification, and flavor-violating decay rates, with implications for collider phenomenology.

Contribution

It provides the most general form of high-scale soft SUSY-breaking parameters considering 1-loop thresholds and demonstrates their impact on unification and decay predictions.

Findings

Gaugino mass unification can be violated by about 10%.

Complete RGE solutions can significantly alter event topology predictions.

Threshold effects cause splitting between couplings that are equal at tree level.

Abstract

We reexamine the renormalization group equations (RGEs) for the dimensionless and dimensionful parameters of the Minimal Supersymmetric Standard Model (MSSM), incorporating 1-loop thresholds. The inclusion of these thresholds necessarily results in splitting between dimensionless couplings which are equal at the tree level. Assuming that the SUSY-breaking mechanism does not introduce new intergenerational couplings, we present the most general form for high-scale, soft-SUSY-breaking (SSB) parameters. With this as our boundary condition, we consider illustrative examples of numerical solutions to the RGEs. In a supersymmetric grand unified theory with the scale of SUSY scalars split from that of gauginos and higgsinos, we find that the gaugino mass unification relation may be violated to the order of 10%. Further, we consider the rate for the flavor violating decay of the lightest stop to charm plus neutralino. We find that using the complete RGE solution as opposed to the commonly used `single-step' integration of the RGEs can qualitatively change the picture of event-topologies from top-squark pair production, or from gluino production if gluino to stop plus top is the dominant gluino decay mode.