On the MSSM Higgsino mass and fine tuning

TL;DR

This paper demonstrates that in the MSSM, including a complete set of soft SUSY breaking terms can reduce fine tuning even with TeV-scale Higgsinos, challenging the common belief that light Higgsinos are necessary for low fine tuning.

Contribution

It introduces a correlation between the Higgsino mass term and soft SUSY-breaking masses, showing this reduces fine tuning in the MSSM.

Findings

Including soft SUSY-breaking terms reduces fine tuning.

TeV-scale Higgsinos can be consistent with low fine tuning.

Higgsinos can account for all dark matter without high fine tuning.

Abstract

It is often argued that low fine tuning in the MSSM necessarily requires a rather light Higgsino. In this note we show that this need not be the case when a more complete set of soft SUSY breaking mass terms are included. In particular an Higgsino mass term, that correlates the $\mu-$term contribution with the soft SUSY-breaking Higgsino masses, significantly reduces the fine tuning even for Higgsinos in the TeV mass range where its relic abundance means it can make up all the dark matter.