Precision Corrections to Fine Tuning in SUSY

TL;DR

This paper refines the calculation of naturalness bounds in supersymmetry by including higher-order effects and threshold corrections, revealing tighter constraints on superpartner masses from LHC data.

Contribution

It introduces improved tuning calculations incorporating RGE resummation, two-loop effects, and threshold corrections, providing more accurate bounds on superpartner masses.

Findings

Tuning bounds now include effects of 1st and 2nd generation squarks.

Heavier gluinos and stops are compatible with tuning constraints.

Natural SUSY is increasingly constrained by LHC results.

Abstract

Requiring that the contributions of supersymmetric particles to the Higgs mass are not highly tuned places upper limits on the masses of superpartners -- in particular the higgsino, stop, and gluino. We revisit the details of the tuning calculation and introduce a number of improvements, including RGE resummation, two-loop effects, a proper treatment of UV vs. IR masses, and threshold corrections. This improved calculation more accurately connects the tuning measure with the physical masses of the superpartners at LHC-accessible energies. After these refinements, the tuning bound on the stop is now also sensitive to the masses of the 1st and 2nd generation squarks, which limits how far these can be decoupled in Effective SUSY scenarios. We find that, for a fixed level of tuning, our bounds can allow for heavier gluinos and stops than previously considered. Despite this, the natural region of supersymmetry is under pressure from the LHC constraints, with high messenger scales particularly disfavored.