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\clearpage
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\section{Results}
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\label{sec:results}
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\begin{figure}[tbh]
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\begin{center}
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\includegraphics[width=0.75\linewidth]{abcd_35pb.png}
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\caption{\label{fig:abcdData}\protect Distributions of SumJetPt
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vs. MET$/\sqrt{\rm SumJetPt}$ for SM Monte Carlo and data. Here we also
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show our choice of ABCD regions.}
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\end{center}
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\end{figure}
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The data, together with SM expectations is presented
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in Figure~\ref{fig:abcdData}. We see 1 event in the
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signal region (region $D$). The Standard Model MC
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expectation is 1.4 events.
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\subsection{Background estimate from the ABCD method}
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\label{sec:abcdres}
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The data yields in the
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four regions are summarized in Table~\ref{tab:datayield}.
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The prediction of the ABCD method is is given by $A\times C/B$ and
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is 1.5 events. (see Table~\ref{tab:datayield}.
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\begin{table}[hbt]
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\begin{center}
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\caption{\label{tab:datayield} Data yields in the four
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regions of Figure~\ref{fig:abcdData}, as well as the predicted yield in region D given
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by A$\times$C / B. The quoted uncertainty
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on the prediction in data is statistical only, assuming Gaussian errors.
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We also show the SM Monte Carlo expectations, scaled to 34.85~pb$^{-1}$.}
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\begin{tabular}{l||c|c|c|c||c}
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\hline
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sample & A & B & C & D & A$\times$C / B \\
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\hline
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$t\bar{t}\rightarrow \ell^{+}\ell^{-}$ & 7.96 & 33.07 & 4.81 & 1.20 & 1.16 \\
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$t\bar{t}\rightarrow \mathrm{other}$ & 0.15 & 0.85 & 0.09 & 0.04 & 0.02 \\
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$Z^0$ + jets & 0.00 & 1.16 & 0.08 & 0.08 & 0.00 \\
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$W^{\pm}$ + jets & 0.00 & 0.10 & 0.00 & 0.00 & 0.00 \\
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$W^+W^-$ & 0.19 & 0.29 & 0.02 & 0.07 & 0.02 \\
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$W^{\pm}Z^0$ & 0.03 & 0.04 & 0.01 & 0.01 & 0.00 \\
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$Z^0Z^0$ & 0.00 & 0.03 & 0.00 & 0.00 & 0.00 \\
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single top & 0.28 & 1.00 & 0.04 & 0.01 & 0.01 \\
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\hline
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total SM MC & 8.61 & 36.54 & 5.05 & 1.41 & 1.19 \\
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\hline
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data & 11 & 36 & 5 & 1 &1.53 $\pm$ 0.86 \\
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\hline
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\end{tabular}
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\end{center}
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\end{table}
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%As a cross-check, we can subtract from the yields in
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%Table~\ref{tab:datayield} the expected DY contributions
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%from Table~\ref{tab:ABCD-DY} in order to get a ``purer''
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%estimate of the $t\bar{t}$ contribution. The result
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%of this exercise is {\color{red} xx} events.
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\subsection{Background estimate from the $P_T(\ell\ell)$ method}
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\label{sec:victoryres}
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The number of data events in region $D'$, which is defined in
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Section~\ref{sec:othBG} to be the same as region $D$ but with the
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$\met/\sqrt{\rm SumJetPt}$ requirement
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replaced by a $P_T(\ell\ell)/\sqrt{\rm SumJetPt}$ requirement
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is $N_{D'}=1$. Thus the BG prediction is
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$N_D = K \cdot K_C \cdot N_{D'} = 1.5$
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where $K=1.5 \pm xx$ as derived in Sec.~\ref{sec:victory} and
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$K_C = 1$.
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Note that if we were to subtract off from region $D'$
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the {\color{red} 0.4 $\pm$ 0.4} DY events estimated from
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Section~\ref{sec:othBG}, the background
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prediction would change to $N_D=0.9 \pm xx$ events.
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%%%TO BE REPLACED
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%{\color{red}As mentioned previously, for the 11/pb analysis
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%we use the $K$ factor from data and take $K=1$.
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%This will change for the full dataset. We will also pay
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%more attention to the statistical errors.}
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%The number of data events in region $D'$, which is defined in
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%Section~\ref{sec:othBG} to be the same as region $D$ but with the
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%$\met/\sqrt{\rm SumJetPt}$ requirement
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%replaced by a $P_T(\ell\ell)/\sqrt{\rm SumJetPt}$ requirement
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%is $N_{D'}=1$. Thus the BG prediction is
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%$N_D = K \cdot K_{\rm fudge} \cdot N_{D'} = 1.5$
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%where we used $K=1.5 \pm xx$ and $K_{\rm fudge}=1.0 \pm 0.0$.
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%Note that if we were to subtract off from region $D'$
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%the {\color{red} 0.4 $\pm$ 0.4} DY events estimated from
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%Section~\ref{sec:othBG}, the background
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%prediction would change to $N_D=0.9 \pm xx$ events.
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%{\color{red} When we do this with a real
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%$K_{\rm fudge}$, the fudge factor will be different
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%after the DY subtraction.}
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As a cross-check, we use the $P_T(\ell \ell)$
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method to also predict the number of events in the
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control region $120<{\rm SumJetPt}<300$ GeV and
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\met/$\sqrt{\rm SumJetPt} > 8.5$. We predict
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$5.6^{+x}_{-y}$ events and we observe 4.
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The results of the $P_T(\ell\ell)$ method are
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summarized in Figure~\ref{fig:victory}.
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\begin{figure}[hbt]
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\begin{center}
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\includegraphics[width=0.48\linewidth]{victory_control.png}
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\includegraphics[width=0.48\linewidth]{victory_sig.png}
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\caption{\label{fig:victory}\protect Distributions of
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tcMet/$\sqrt{\rm SumJetPt}$ for the control and signal region.
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We show the oberved distributions in both Monte Carlo and data.
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We also show the distributions predicted from
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${P_T(\ell\ell)}/\sqrt{\rm SumJetPt}$ in both MC and data.}
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\end{center}
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\end{figure}
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\subsection{Summary of results}
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To summarize: we see no evidence for an anomalous
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rate of opposite sign isolated dilepton events
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at high \met and high SumJetPt. The extraction of
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quantitative limits on new physics models is discussed
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in Section~\ref{sec:limit}. |
