Post-LHC7 fine-tuning in the minimal supergravity/CMSSM model with a 125 GeV Higgs boson

Authors

Howard Baer, University of OklahomaFollow
Vernon Barger, University of WisconsinFollow
Peisi Huang, University of WisconsinFollow
Dan Mickelson, University of OklahomaFollow
Azar Mustafayev, University of HawaiiFollow
Xerxes Tata, University of HawaiiFollow

Document Type

Article

Date of this Version

2013

Citation

PHYSICAL REVIEW D 87, 035017 (2013)

Comments

Copyright 2013 American Physical Society

DOI: 10.1103/PhysRevD.87.035017

Abstract

The recent discovery of a 125 GeV Higgs-like resonance at LHC, coupled with the lack of evidence for weak scale supersymmetry (SUSY), has severely constrained SUSY models such as minimal supergravity (mSUGRA)/CMSSM. As LHC probes deeper into SUSY model parameter space, the little hierarchy problem—how to reconcile the Z and Higgs boson mass scale with the scale of SUSY breaking—will become increasingly exacerbated unless a sparticle signal is found. We evaluate two different measures of fine-tuning in the mSUGRA/CMSSM model. The more stringent of these, [?], includes effects that arise from the high-scale origin of the mSUGRA parameters while the second measure, [?], is determined only by weak scale parameters: hence, it is universal to any model with the same particle spectrum and couplings. Our results incorporate the latest constraints from LHC7 sparticle searches, LHCb limits from B_S [?] and also require a light Higgs scalar with m_h ~ 123-127 GeV. We present fine-tuning contours in the m₀ vs m_1/2 plane for several sets of A₀ and tan [?] values. We also present results for [?] and [?] from a scan over the entire viable model parameter space. We find a [?] [?] 10³, or at best 0.1%, fine-tuning. For the less stringent electroweak fine-tuning, we find [?] [?] 10², or at best 1%, fine-tuning. Two benchmark points are presented that have the lowest values of [?] and [?]. Our results provide a quantitative measure for ascertaining whether or not the remaining mSUGRA/CMSSM model parameter space is excessively fine-tuned and could provide impetus for considering alternative SUSY models.