Search for direct production of electroweakinos in final states with one lepton, missing transverse momentum and a Higgs
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Regular Article - Experimental Physics
Search for direct production of electroweakinos in final states with one lepton, missing transverse momentum √ and a Higgs boson decaying into two b-jets in pp collisions at s = 13 TeV with the ATLAS detector ATLAS Collaboration CERN, 1211 Geneva 23, Switzerland Received: 20 September 2019 / Accepted: 15 May 2020 / Published online: 1 August 2020 © CERN for the benefit of the ATLAS collaboration 2020
Abstract The results of a search for electroweakino pair production pp → χ˜ 1± χ˜ 20 in which the chargino (χ˜ 1± ) decays into a W boson and the lightest neutralino (χ˜ 10 ), while the heavier neutralino (χ˜ 20 ) decays into the Standard Model 125 GeV Higgs boson and a second χ˜ 10 are presented. The signal selection requires a pair of b-tagged jets consistent with those from a Higgs boson decay, and either an electron or a muon from the W boson decay, together with missing transverse momentum from the corresponding neutrino and the stable neutralinos. The analysis is based on data corresponding to √ 139 fb−1 of s = 13 TeV pp collisions provided by the Large Hadron Collider and recorded by the ATLAS detector. No statistically significant evidence of an excess of events above the Standard Model expectation is found. Limits are set on the direct production of the electroweakinos in simplified models, assuming pure wino cross-sections. Masses of χ˜ 1± /χ˜ 20 up to 740 GeV are excluded at 95% confidence level for a massless χ˜ 10 .
1 Introduction The Standard Model (SM) is a remarkably successful theory, yet it is clear that this theory is not a complete description of nature. The discovery in 2012 of the SM Higgs boson [1–4], by the ATLAS and CMS collaborations, confirmed the mechanism of the electroweak symmetry breaking and highlighted the hierarchy problem [5–8]. Supersymmetry (SUSY) [9– 14], a theoretical extension to the SM, resolves the hierarchy problem by introducing a new fermion (boson) supersymmetric partner for each boson (fermion) in the SM. In SUSY models that conserve R-parity [15], the SUSY particles are produced in pairs. Furthermore, the lightest supersymmetric particle (LSP) is stable and weakly interacting, thus constituting a viable dark-matter candidate [16,17]. e-mail:
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In SUSY scenarios the partners of the SM Higgs boson (h) and the gauge bosons, known as the higgsinos, winos (partners of the SU(2)L gauge fields), and bino (partner of the U(1) gauge field) are collectively referred to as electroweakinos. Charginos χ˜ i± (i = 1, 2) and neutralinos χ˜ 0j ( j = 1, 2, 3, 4) are the electroweakino mass eigenstates which are linear superpositions of higgsinos, winos, and bino. For the models considered in this paper, the lightest neutralino (χ˜ 10 ) is a bino-like LSP. The lightest chargino (χ˜ 1± ) and next-to-lightest neutralino (χ˜ 20 ) are wino-like and nearly mass degenerate. Naturalness considerations [18,19] suggest that the lightest of the electroweakinos have masses near the electroweak scale. In scenarios where the strong
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