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\section{Search in the Same-sign Dilepton Final State}
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\label{sec:ss}
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\begin{figure*}[!ht]
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\centering
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%\begin{center}
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\begin{tabular}{cc}
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\subfloat[] {\includegraphics[width=0.5\textwidth]{HCPPlots/SS_B1.pdf}} &
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\subfloat[] {\includegraphics[width=0.4\textwidth]{HCPPlots/T2bb_interpretation.pdf}} \\
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\end{tabular}
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\caption{
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Interpretation of the results of the search in (a) the same-sign dilepton final state for
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bottom squark pair production with $\tilde{b}\to t\chim$ depicted in Fig.~\ref{fig:diagrams}(d), and (b)
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the all-hadronic final state for bottom squark pair production with $\tilde{b}\to b\lsp$ depicted in Fig.~\ref{fig:diagrams}(c).
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\label{fig:ss_interpretation}
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}
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%\end{center}
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\end{figure*}
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This section presents a search in the same-sign (SS) dilepton final state, based on 10.5 fb$^{-1}$.
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A wide variety of new physics scenarios may produce events with SS leptons, which provide a very clean
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final state due to low SM background expectations. In particular, this final state is sensitive to
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direct pair production of bottom squarks with $\tilde{b}\to t \chim \to t W \lsp$ depicted in Fig.~\ref{fig:diagrams}(d),
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as well as to gluino-mediated production of top and bottom squarks.
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We select events with two leptons (e or $\mu$) with \pt\ $>$ 20 GeV and dilepton invariant mass $m_{\ell\ell}>8$ GeV.
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We reject events with a third lepton with \pt\ $>$ 10 GeV that forms an opposite-sign
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same-flavor pair with $76 < m_{\ell\ell} < 106$ GeV with either selected lepton, to suppress
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the background from WZ and ZZ. We require the presence of at least two jets with \pt\ $>$ 40 GeV.
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This analysis is an extension of a previous search in the same-sign dilepton final state~\cite{ref:ss_inclusive}.
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In that analysis, the background is dominated by \ttljets\ where one lepton is from the W decay and the other
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lepton is produced in the decay of one of the b-jets. In this analysis we require the presence of at least two
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b-tagged jets (using CSVM). The requirement that both b-jets are identified and well-separated from the selected leptons
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reduces the \ttljets\ background by an order of magnitude.
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There are three sources of SM background passing the above preselection.
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The first background source is referred to as ``fake leptons'' and includes leptons from heavy-flavor decay,
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misidentified hadrons, muons from meson decay in flight, or electrons from unidentified photon conversions.
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This background is estimated from a sample of events with at least one lepton that passes a loose selection
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but fails the full analysis identification and isolation requirements. This sample is weighted by the probability
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for a fake lepton satisfying the loose selection to also pass the analysis selection, which is determined based
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on studies of fake
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leptons in jet events. The second background, estimated from MC, consists of rare SM processes and is dominated
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by $t\bar{t}$W and $t\bar{t}$Z. The systematic uncertainty on both the fake lepton and rare backgrounds is 50\%.
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A third, small background contribution is from ``charge flips'' and consists of events with opposite-sign (OS) leptons
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where one of the leptons is an electron whose charge is misreconstructed.
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This background is estimated from an OS dilepton data sample, weighted by the electron charge misreconstruction probability,
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which is extracted from studies of Z$\to$ee events in data and MC.
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%This background is based on MC predictions, which are validated using a sample of Z$\to e^+e^-$ events.
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Signal regions are defined by placing additional requirements on the jet multiplicity, b-tagged jet multiplicity,
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\met, and $H_T$, defined as the scalar sum of the transverse momenta of selected jets.
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The observed data yields in all signal regions are in good agreement with the SM background expectations;
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see Ref.~\cite{ref:ss} for the full quantitative results. The signal region that is most sensitive to
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bottom squark pair production with $\tilde{b}\to t \chim$ depicted in Fig.~\ref{fig:diagrams}(d)
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has at least four jets, \met\ $>$ 120 GeV and
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$H_T$ $>$ 200 GeV. In this region we observe 1 event in data and predict 2.22 $\pm$ 0.96 events.
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The results are used to exclude a region of the model parameter space in Fig.~\ref{fig:ss_interpretation}(a),
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which demonstrates that our search probes bottom squarks with masses up to 450 GeV.
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Naturalness considerations favor a bottom squark with mass not exceeding 500--700 GeV, similar to the constraint
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on the top squark mass.
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Several additional interpretations for models with gluino-mediated top and
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bottom squark production are presented in Ref.~\cite{ref:ss}.
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%\input{ss_table.tex}
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%compared to the SM background expectations in
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%Table~\ref{tab:ss}. Good agreement is observed between the data and the expected background in all signal regions.
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%\begin{table}
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%\centering
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%\caption{Please write your table caption here}
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%\label{tab-1} % Give a unique label
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%% For LaTeX tables you can use
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%\begin{tabular}{lll}
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%\hline
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%first & second & third \\\hline
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%number & number & number \\
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%number & number & number \\\hline
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%\end{tabular}
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%% Or use
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%\vspace*{5cm} % with the correct table height
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%\end{table}
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