[Paper Review] Natural Supersymmetry after the LHC8

Manuel Drees, Jong Soo Kim|arXiv (Cornell University)|Nov 13, 2015

Particle physics theoretical and experimental studies3 citations

TL;DR

This study evaluates natural supersymmetry scenarios using LHC Run 1 data, scanning 22,000 points in a six-dimensional parameter space where higgsinos are the lightest supersymmetric particle, and third-generation squarks, stops, and gluinos are relatively light. It finds that models with m~t1 < 660 GeV or m~G > 1180 GeV remain viable after stringent LHC searches, highlighting the complementarity of multiple search channels in constraining the parameter space.

ABSTRACT

In this work, we present limits on natural supersymmetry inspired scenarios based on searches in data taken during run 1 of the LHC. We consider a set of 22000 model points in a six dimensional parameter space. The resulting mass spectra feature higgsinos as the lightest supersymmetric particle, as well as relatively light third generation SU(2) doublet squarks and SU(2) singlet stops and gluinos while assuming a Standard Model like Higgs boson. All remaining supersymmetric particles and Higgs bosons are assumed to be decoupled. We check each parameter set against a large number of LHC searches as implemented in the public code CheckMATE. These searches show a considerable degree of complementarity, i.e. in general many searches have to be considered in order to check whether a given scenario is allowed. We delineate allowed and excluded regions in parameter space. For example, we nd that all scenarios where either m~ t1 660 GeV and m~ > 1180 GeV remain allowed.

Motivation & Objective

• To assess the viability of natural supersymmetry scenarios following LHC Run 1 data.
• To identify regions of the six-dimensional parameter space that remain consistent with experimental constraints.
• To evaluate the complementarity of multiple LHC searches in excluding or allowing specific supersymmetric models.
• To determine the mass limits on the lightest stop and gluino that are still compatible with naturalness and LHC data.

Proposed method

• A scan of 22,000 model points across a six-dimensional supersymmetric parameter space, assuming a Standard Model-like Higgs boson.
• Assumption that all supersymmetric particles except higgsinos, third-generation squarks, stops, and gluinos are decoupled.
• Application of the CheckMATE public code to evaluate each model point against a comprehensive set of LHC search analyses.
• Use of multiple search channels to assess constraints, leveraging their complementarity to improve exclusion sensitivity.
• Identification of allowed and excluded regions in the parameter space based on combined search results.

Experimental results

Research questions

• RQ1 Which regions of the natural supersymmetry parameter space remain consistent with LHC Run 1 data?
• RQ2 How do different LHC search channels complement each other in constraining supersymmetric models?
• RQ3 What are the mass limits on the lightest stop and gluino that preserve naturalness and evade experimental exclusion?
• RQ4 To what extent do the constraints from LHC searches rule out specific combinations of stop and gluino masses?

Key findings

• Models with m~t1 < 660 GeV remain allowed by LHC searches, indicating that relatively light stops are still viable.
• Scenarios with m~G > 1180 GeV are also not excluded, suggesting that heavy gluinos are consistent with current data.
• The complementarity of multiple LHC searches is essential, as no single search channel can fully constrain the parameter space.
• The study identifies a significant region of the parameter space that remains consistent with both naturalness and LHC Run 1 constraints.