Abstract
The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider (LHC) are reported. The search is based on proton-proton collision data at a centre-of-mass energy $\sqrt{s} = 8$ TeV collected in 2012, corresponding to an integrated luminosity of 20 fb$^{-1}$. No significant excess above the Standard Model expectation is observed. Limits are set on the parameters of a minimal universal extra dimensions model, excluding a compactification radius of $1/R_c=950$ GeV for a cut-off scale times radius ($\Lambda R_c$) of approximately 30, as well as on sparticle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV.
Highlights
Supersymmetry (SUSY) [1,2,3,4,5,6,7,8,9] postulates the existence of particles which differ by half a unit of spin from their Standard Model (SM) partners
There are six parameters which can be varied to obtain different phenomenologies: tan β, m1/2, A0 and the sign of μ, defined above, as well as the squared mass terms of the two Higgs doublets: m2H1 and m2H2. These parameters are set as follows: tan β = 10, μ > 0, m2H2 = 0; m1/2 and m2H1 are chosen such that the next-to-lightest SUSY particle (NLSP) is a tau-sneutrino with properties satisfying Big Bang Nucleosynthesis constraints; A0 is chosen to maximise the mass of the lightest Higgs boson
The normalisation factors of the dominant backgrounds after the fit are found to be O(0.7–0.9) for tt(with the lowest value found in the soft dimuon channel), O(0.5–0.9) for W +jets and O(0.9) for Z+jets
Summary
Supersymmetry (SUSY) [1,2,3,4,5,6,7,8,9] postulates the existence of particles (sparticles) which differ by half a unit of spin from their Standard Model (SM) partners. If the LSP is stable owing to R-parity conservation [15,16,17,18,19] and only weakly interacting, it escapes detection, leading to missing transverse momentum (pmTiss and its magnitude ETmiss) in the final state. This paper presents a search with the ATLAS detector [20, 21] for SUSY in final states containing jets, at least one isolated lepton (electron or muon) and large ETmiss. To enhance the sensitivity to gluino or squark production, high and low jet multiplicity signal regions are defined Previous searches in these final states have been conducted by the ATLAS [22, 23] and CMS [24] collaborations using their full 2011 dataset at a centre-of-mass energy of 7 TeV.
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