Combined collider constraints on neutralinos and charginos

Athron, P. et al. (2019) Combined collider constraints on neutralinos and charginos. European Physical Journal C, 79(5), 395. (doi:10.1140/epjc/s10052-019-6837-x)

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Abstract

Searches for supersymmetric electroweakinos have entered a crucial phase, as the integrated luminosity of the Large Hadron Collider is now high enough to compensate for their weak production cross-sections. Working in a framework where the neutralinos and charginos are the only light sparticles in the Minimal Supersymmetric Standard Model, we use gambit to perform a detailed likelihood analysis of the electroweakino sector. We focus on the impacts of recent ATLAS and CMS searches with 36 fb−1 of 13 TeV proton-proton collision data. We also include constraints from LEP and invisible decays of the Z and Higgs bosons. Under the background-only hypothesis, we show that current LHC searches do not robustly exclude any range of neutralino or chargino masses. However, a pattern of excesses in several LHC analyses points towards a possible signal, with neutralino masses of (mχ~01,mχ~02,mχ~03,mχ~04) = (8-155, 103-260, 130-473, 219-502) GeV and chargino masses of (mχ~±1,mχ~±2) = (104-259, 224-507) GeV at the 95% confidence level. The lightest neutralino is mostly bino, with a possible modest Higgsino or wino component. We find that this excess has a combined local significance of 3.3σ, subject to a number of cautions. If one includes LHC searches for charginos and neutralinos conducted with 8 TeV proton-proton collision data, the local significance is lowered to 2.9σ. We briefly consider the implications for dark matter, finding that the correct relic density can be obtained through the Higgs-funnel and Z-funnel mechanisms, even assuming that all other sparticles are decoupled. All samples, gambit input files and best-fit models from this study are available on Zenodo.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Buckley, Dr Andy
Authors: Athron, P., Balázs, C., Buckley, A., Cornell, J. M., Danninger, M., Farmer, B., Fowlie, A., Gonzalo, T. E., Harz, J., Jackson, P., Kudzman-Blais, R., Kvellestad, A., Martinez, G. D., Petridis, A., Raklev, A., Rogan, C., Scott, P., Sharma, A., White, M., and Zhang, Y.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:European Physical Journal C
Publisher:Springer
ISSN:1434-6044
ISSN (Online):1434-6052
Published Online:08 May 2019
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in European Physical Journal C 79(5): 395
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
169022Jet substructure and new physics studies with the ATLAS experimentAndrew BuckleyThe Royal Society (ROYSOC)UF110191P&S - Physics & Astronomy
300260New physics studies with heavy flavour at the LHCAndrew BuckleyThe Royal Society (ROYSOC)UF160548P&S - Physics & Astronomy