Non-universal gaugino masses and fine tuning implications for SUSY searches in the MSSM and the GNMSSM

TL;DR

This paper investigates how non-universal gaugino masses at the unification scale can reduce fine tuning in the MSSM and GNMSSM, considering experimental constraints, and explores the implications for SUSY searches at the LHC.

Contribution

It demonstrates that allowing non-universal gaugino masses can significantly lower fine tuning in SUSY models, especially in the GNMSSM, and connects these regions to specific theoretical models.

Findings

Low-fine tuned points align with gaugino mass ratios predicted by unified and string models.

Fine tuning in the MSSM remains large (~1:60), but is reduced to below 1:20 in the GNMSSM.

Compressed SUSY spectra at low fine tuning weaken LHC bounds on colored states.

Abstract

For the case of the MSSM and the most general form of the NMSSM (GNMSSM) we determine the reduction in the fine tuning that follows from allowing gaugino masses to be non-degenerate at the unification scale, taking account of the LHC8 bounds on SUSY masses, the Higgs mass bound, gauge coupling unification and the requirement of an acceptable dark matter density. We show that low-fine tuned points fall in the region of gaugino mass ratios predicted by specific unified and string models. For the case of the MSSM the minimum fine tuning is still large, approximately 1:60 allowing for a 3 GeV uncertainty in the Higgs mass (1:500 for the central value), but for the GNMSSM it is below 1:20. We find that the spectrum of SUSY states corresponding to the low-fine tuned points in the GNMSSM is often compressed, weakening the LHC bounds on coloured states. The prospect for testing the remaining low-fine-tuned regions at LHC14 is discussed.