Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in $ \sqrt{s} $ = 8 TeV pp collisions with the ATLAS detector

Abstract

A search for the direct production of charginos and neutralinos in final states with three leptons and missing transverse momentum is presented. The analysis is based on 20.3 fb −1 of √ s = 8 TeV proton-proton collision data delivered by the Large HadronCollider and recorded with the ATLAS detector. Observations are consistent with the Standard Model expectations and limits are set in R-parity-conserving phenomenological Minimal Supersymmetric Standard Models and in simplified supersymmetric models, significantly extending previous results. For simplified supersymmetric models of direct chargino (χ ± 1 ) and next-to-lightest neutralino (χ 0 2 ) production with decays to lightest neutralino (χ 0 1 ) via either all three generations of sleptons, staus only, gauge bosons, or Higgs bosons,χ ± 1 andχ 0 2 masses are excluded up to 700 GeV, 380 GeV, 345 GeV, or 148 GeV respectively, for a masslessχ 0 1 . Keywords: Hadron-Hadron ScatteringArXiv ePrint: 1402.7029Open Access, Copyright CERN, for the benefit of the ATLAS Collaboration. The ATLAS collaboration 30 IntroductionSupersymmetry (SUSY) [1][2][3][4][5][6][7][8][9] proposes the existence of supersymmetric particles, with spin differing by one-half unit with respect to that of their Standard Model (SM) partners. Charginos,χ ± 1,2 , and neutralinos,χ 0 1,2,3,4 , collectively referred to as electroweakinos, are the ordered mass eigenstates formed from the linear superposition of the SUSY partners of the Higgs and electroweak gauge bosons (higgsinos, winos and binos). Based on naturalness arguments [10,11], the lightest electroweakinos are expected to have mass of order 100 GeV and be accessible at the Large Hadron Collider (LHC). In the R-parity-conserving minimal supersymmetric extension of the SM (MSSM) [12][13][14][15][16], SUSY particles are pair-produced and the lightest SUSY particle (LSP), assumed in many models to be theχ 0 1 , is stable. Charginos and neutralinos can decay into leptonic final states via superpartners of neutrinos (ν, sneutrinos) or charged leptons (l, sleptons), or via W , Z or Higgs (h) bosons (χ ± i → ℓ ±ν , νl ± , W ±χ 0 j , Zχ JHEP04(2014)169µ or τ , referred to as leptons in the following) and missing transverse momentum originating from the two undetected LSPs and the neutrinos. The analysis is based on 20.3 fb −1 of proton-proton collision data recorded by ATLAS at a centre-of-mass energy of √ s = 8 TeV.Previous searches for charginos and neutralinos are documented in refs [17][18][19] by ATLAS, and in ref. [20] by CMS. Similar searches were conducted at the Tevatron [21, 22]. At LEP [23][24][25][26][27], searches for direct chargino production set a model-independent lower limit of 103.5 GeV at 95% confidence level (CL) on the mass of promptly decaying charginos. SUSY scenariosAmong the electroweakino pair-production processes leading to three leptons in the final state,χ ± 1χ 0 2 production has the largest cross-section in most of the MSSM parameter space. Several simplified supersymmetric models ("simplified models" [28])...

GUT-inspired SUSY and the muon g-2 anomaly: Prospects for LHC 14 TeV

“…1(a) we show in the (m χ It has been shown [24,28,69] that the parameter space corresponding to the Z/hresonance region can be probed at the LHC by 3-lepton searches for EW-ino production and 2-lepton searches for direct slepton production. The bounds from 3-lepton searches are much stronger in the presence of an intermediate slepton between the mass of the chargino and neutralino [46,47]. They are approximately shown as red dashed lines in Fig.…”

Pseudo-goldstino and electroweak gauginos at the LHC

“…Finally, we note that the LHC searched the neutralinos and charginos with leptons plus missing E T at 7 and 8 TeV, and the observed events are in agreement with the SM backgrounds (no excess), which gave some limits on the relevant parameter space [45][46][47]. Since in our scenario the signals are quite rare compared with the huge SM backgrounds (as shown in our results, only at 14 TeV LHC with a rather high luminosity can our signals be possibly accessible), the current LHC limits at 7 and 8 TeV with rather limited luminosities are not yet able to constrain the scenario under our consideration.…”

The higgsino–singlino world at the large hadron collider

“…The trilepton and missing transverse energy ( E T ) signal at the LHC was first investigated in [22,23]. The ATLAS [19,20] and CMS [21] searches for trilepton and large missing transverse momentum at the LHC at √ s = 8 TeV with an integrated luminosity of 20 fb −1 put already strict constraints on gaugino pair production in a simplified MSSM model. They consider wino-like lightest charginoχ ± 1 , heavier wino-like neutralinoχ 0 2 and a bino- andχ 0 2 masses up to 345 GeV are excluded.…”

“…The signature is three isolated leptons and missing transverse energy. This process is known as the trilepton signal and the corresponding searches has been performed by ATLAS and CMS [19][20][21]. Studies of the discovery potential at 14 TeV has been studied in [22,23] and in Ref.…”