Naturalness-guided Gluino Mass Bound from the Minimal Mixed Mediation of SUSY Breaking

TL;DR

This paper proposes a minimal mixed mediation model in supersymmetry that links naturalness to gluino mass, allowing heavier stops while maintaining electroweak naturalness, and predicts gluino masses within LHC Run II reach.

Contribution

It introduces a minimal mixed mediation framework where the focus point of the Higgs mass parameter is at 3-4 TeV, making the electroweak naturalness primarily dependent on the gluino mass rather than stop mass.

Findings

Gluino mass constrained to 1.6-2.2 TeV for naturalness.

Heavy stops (~3-4 TeV) compatible with natural electroweak scale.

Gluino masses within LHC Run II discovery range.

Abstract

In order to significantly reduce the fine-tuning associated with the electroweak symmetry breaking in the minimal supersymmetric standard model (MSSM), we consider not only the minimal gravity mediation effects but also the minimal gauge mediation ones for a common supersymmetry breaking source at a hidden sector. In this "Minimal Mixed Mediation model," the minimal forms for the Kahler potential and the gauge kinetic function are employed at tree level. The MSSM gaugino masses are radiatively generated through the gauge mediation. Since a "focus point" of the soft Higgs mass parameter, m_{h_u}^2 appears around 3-4 TeV energy scale in this case, m_{h_u}^2 is quite insensitive to stop masses. Instead, the naturalness of the small m_{h_u}^2 is more closely associated with the gluino mass rather than the stop mass unlike the conventional scenario. As a result, even a 3-4 TeV stop mass, which is known to explain the 125 GeV Higgs mass at three-loop level, can still be compatible with the naturalness of the electroweak scale. On the other hand, the requirements of various fine-tuning measures much smaller than 100 and |\mu| < 600 GeV constrain the gluino mass to be 1.6 TeV < M_3 < 2.2 TeV, which is well-inside the discovery potential range of LHC RunII.