Closing up a light stop window in natural SUSY at LHC

Archil Kobakhidze; Ning Liu; Lei Wu; Jin Min Yang; Mengchao Zhang

doi:10.1016/j.physletb.2016.02.003

paper

Closing up a light stop window in natural SUSY at LHC

arXiv:1511.02371 · doi:10.1016/j.physletb.2016.02.003

Abstract

Top squark (stop) plays a key role in the radiative stability of the Higgs boson mass in supersymmetry (SUSY). The LHC searches for stop have made a great progress and tightly constrained the stop mass during Run-1. In this work, we use the LHC Run-1 data to determine the lower mass limit of the right-handed stop in a natural SUSY scenario, where the higgsinos $χ ~_{1, 2}^{0}$ and $χ ~_{1}^{\pm}$ are light and nearly degenerate. We find that the stop mass has been excluded up to 430 GeV for $m_{χ ~_{1}^{0}} ≲ 250$ GeV and to 540 GeV for $m_{χ ~_{1}^{0}} ≃ 100$ GeV by the Run-1 SUSY searches for $2 b + E_{T}^{mi ss}$ and $1 ℓ + j e t s + E_{T}^{mi ss}$ , respectively. In a small strip of parameter space with $m_{χ ~_{1}^{0}} ≳ 190$ GeV, the stop mass can still be as light as 210 GeV and compatible with the Higgs mass measurement and the monojet bound. The 14 TeV LHC with a luminosity of 20 fb $^{- 1}$ can further cover such a light stop window by monojet and $2 b + E_{T}^{mi ss}$ searches and push the lower bound of the stop mass to 710 GeV. We also explore the potential to use the Higgs golden ratio, $D_{γ γ} = σ (pp \to h \to γ γ) / σ (pp \to h \to Z Z^{*} \to 4 ℓ^{\pm})$ , as a complementary probe for the light and compressed stop. If this golden ratio can be measured at percent level at the high luminosity LHC (HL-LHC) or future $e^{+} e^{-}$ colliders, the light stop can be excluded for most of the currently allowed parameter region.

Discussions added, version accepted by Phys. Lett. B

Closing up a light stop window in natural SUSY at LHC

Abstract

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