Search for Supersymmetry in Events with Three Leptons and Missing Transverse Momentum in $\sqrt{s}=7\mathrm{TeV}$ $pp$ Collisions with the ATLAS Detector

A search for the weak production of charginos and neutralinos decaying to a final state with three leptons (electrons or muons) and missing transverse momentum is presented. The analysis uses $2.06{\mathrm{fb}}^{-1}$ of $\sqrt{s}=7\mathrm{TeV}$ proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with standard model expectations in two signal regions that are either depleted or enriched in $Z$-boson decays. Upper limits at 95% confidence level are set in $R$-parity conserving phenomenological minimal supersymmetric and simplified models. For the simplified models, degenerate lightest chargino and next-to-lightest neutralino masses up to 300 GeV are excluded for mass differences from the lightest neutralino up to 300 GeV.

Figure 1

$E_{\mathrm{T}}^{\mathrm{miss}}$ distributions for events in signal regions SR1 (left) and SR2 (right). The error band includes both statistical and systematic uncertainty, while the errors on the data points are statistical only. The SUSY reference point used in SR1 is described in the text.

Figure 2

Observed and expected 95% C.L. limit contours for chargino and neutralino production in the pMSSM (upper) and simplified model (lower) scenarios. For the simplified models, the 95% C.L. upper limit on the production cross-section is also shown. Interpolation is used to account for the discreteness of the signal grids.