MSSM $\mathbf{H^\pm \rightarrow \chi^\pm \chi^0}$ Searches

\def\met{\mbox{$\rm {\hbox{E\kern-0.5em\lower-.1ex\hbox{/}}}_T$}} In the Minimum Supersymmetric Standard Model (MSSM), the charged Higgs boson ($ H^\pm$) can decay into a chargino-neutralino ($\chi^\pm \chi^0 $) pair producing the final states containing three leptons (electron/muon) and missing transverse energy ($3l+\met$). The early ATLAS data of approximately $200\ pb^{-1}$ can be investigated to determine the $3l+\met$ background shapes for numerous new physics searches beyond the SM. Monte Carlo studies related to such background determination in $3l+\met$ channel along with a preliminary sensitivity study for the MSSM $H^\pm \rightarrow \chi^\pm \chi^0 \rightarrow 3l+\met$ search are presented here.