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\section{Overview and Strategy for Background Determination} |
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\label{sec:overview} |
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[THIS SECTION IS NOW MORE OR LESS OK. NEED TO FIX THE ``XX'' IN |
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FORWARD SECTION REFERENCES] |
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We are searching for a $t\bar{t}\chi^0\chi^0$ or $W b W \bar{b} \chi^0 \chi^0$ final state |
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(after top decay in the first mode, the final states are actually the same). So to first order |
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this is ``$t\bar{t} +$ extra \met''. |
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We work in the $\ell +$ jets final state, where the main background is $t\bar{t}$. We look for |
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\met\ inconsistent with $W \to \ell \nu$. We do this by concentrating on the $\ell \nu$ transverse |
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mass ($M_T$), since except for resolution effects, $M_T < M_W$ for $W \to \ell \nu$. Thus, the |
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mass ($M_T$), since except for resolution and W-off-shell effects, $M_T < M_W$ for $W \to \ell \nu$. Thus, the |
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initial analysis is simply a counting experiment in the tail of the $M_T$ distribution. |
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The event selection is one-and-only-one high \pt\ isolated lepton, four or more jets, and |
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some moderate \met\ cut. At least one of the jets has to be btagged to reduce $W+$ jets. |
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an \met\ cut. At least one of the jets has to be btagged to reduce $W+$ jets. |
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The event sample is then dominated by $t\bar{t}$, but there are also contributions from $W+$ jets, |
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single top, dibosons, as well as rare SM processes such as $ttW$. |
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after carefully accounting for possible |
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data/MC differences. |
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In Section XX we will describe the analysis of various Control Regions |
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The search is performed in a number of Signal Regions (SRs) defined |
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by minimum requirements on \met\ and $M_T$. The SRs |
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are defined in Section~\ref{sec:SR}. |
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In Section~\ref{sec:CR} we will describe the analysis of various Control Regions |
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(CRs) that are used to test the Monte Carlo model and, if necessary, |
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to extract data/MC scale factors. In this section we give a |
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general description of the procedure. The details of how the |
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final background prediction is assembled are given in Section XX. |
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final background prediction is assembled are given in Section~\ref{sec:bkg_pred}. |
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The search is performed in a number of signal regions defined |
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by minimum requirements on \met\ and $M_T$. These signal |
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regions are defined in Section XX. |
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% Sophisticated fully ``data driven'' techniques are not really needed. |
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