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This analysis uses several different control regions in addition to the signal regions. |
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All of these different regions are defined in this section. |
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Figure~\ref{fig:venndiagram} illustrates the relationship between these regions. |
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The preselection sample is based on the following criteria |
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\subsection{Single Lepton Selections} |
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The single lepton preselection sample is based on the following criteria |
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\begin{itemize} |
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\item satisfy the trigger requirement (see |
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Table.~\ref{tab:DatasetsData}) |
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Table.~\ref{tab:DatasetsData}). Dilepton triggers are used only for the dilepton control region. |
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\item select events with one high \pt\ electron or muon, requiring |
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\begin{itemize} |
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\item $\pt>30~\GeVc$ and $|\eta|<2.5(2.1)$ for \E(\M) |
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\item satisfy the identification and isolation requirements detailed |
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in~\cite{ref:osznote} for electrons and in~\cite{ref:osznote} for muons |
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in the same-sign SUSY analysis (SUS-11-010) for electrons and the opposite-sign |
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SUSY analysis (SUS-11-011) for muons |
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\end{itemize} |
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\item require at least 4 PF jets in the event with $\pt>30~\GeV$ |
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within $|\eta|<2.5$, out of which at least 1 is b-tagged based on |
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the SSV medium working point [CITE]. |
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within $|\eta|<2.5$ |
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\item require moderate $\met>50~\GeV$ |
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\end{itemize} |
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|
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A benchmark signal sample is selected by tightening the \met\ and |
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adding an \mt\ requirement |
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Table~\ref{tab:preselectionyield} shows the yields in data and MC without any corrections for this preselection region. |
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|
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In addition, we count the number of SSV medium working point b-tags, $N_{b-tag}$. |
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|
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Currently, we focus on the muon channel because it is cleaner (the QCD contribution is negligible) |
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and the triggers are simpler (we use single muon triggers, as opposed to electron + 3-jet triggers). |
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We will add the electron channel, time permitting. However, since this is a systematics-dominated |
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analysis, increasing the statistics by adding the electrons is not expected to significantly improve |
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the sensitivity, especially because the electron selection efficiency is smaller and the systematic |
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uncertainty associated with the QCD background is larger. |
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|
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We then define the following subsamples within this preselection sample: |
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\begin{itemize} |
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\item $N_{b-tag} = 0$, i.e. b-veto region $\to$ used to validate the lepton + jets bkg estimation method (see Section~\ref{sec:bkg_singlelep}). |
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For raw yields prior to any corrections see Tables~\ref{tab:bvetoyieldpeak} and ~\ref{tab:bvetoyieldtail}. |
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% |
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\item $N_{b-tag} \ge 1 $, i.e. b-tagged region |
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For raw yields prior to any corrections see Table~\ref{tab:btagpreselection}. |
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% |
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\begin{itemize} |
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\item $\met>100~\GeV$ |
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\item $\mt>150~\GeV$ |
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\item with $\met > 100 \GeV$, $ 60 < \mt < 100 \GeV$, and without an additional isolated track veto $\to$ used to normalize top bkg (see Section~\ref{sec:topnorm}). |
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For raw yields prior to any corrections see Table~\ref{tab:btagpeakregionnotrkiso}. |
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% |
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\item with an additional isolated track veto, $\met > 100 \GeV$, $\mt > 150 \GeV$ $\to$ used as signal region |
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For raw yields prior to any corrections see Table~\ref{tab:btagtailaftertrkiso}. As this is our signal region, only MC is shown at this point. |
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\end{itemize} |
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\end{itemize} |
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|
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%For the signal regions, we then furthermore require $\met>100~\GeV$ while some of the background predictions and scale factors |
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%are done for both \met |
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%requirements to show stability of the method. |
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%Within each of these subsamples we then define an \mt peak ($60 < \mt < 100~\GeV$) region and an \mt tail ($\mt > 150~\GeV$) region |
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% |
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%We generally use the \mt peak region yields in data and multiply it by the ratio of tail divided by peak in MC times appropriate corrections |
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%in order to estimate the background in data in the tail region. |
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|
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{\bf We have not looked at the data in the signal region after the first 1 fb$^{-1}$ of data.} |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{c|c} |
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\hline |
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\hline |
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\end{tabular} |
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\caption{ Raw Data and MC predictions without any corrections are shown after preselection. \label{tab:preselectionyield}} |
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\end{center} |
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\end{table} |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{c|c} |
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\hline |
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\hline |
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\end{tabular} |
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\caption{ Raw Data and MC predictions without any corrections are shown for the b-veto peak region ($\met > 100 \GeV$ and $60 < \mt < 100 \GeV$). |
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\label{tab:bvetoyieldpeak}} |
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\end{center} |
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\end{table} |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{c|c} |
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\hline |
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\hline |
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\end{tabular} |
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\caption{ Raw Data and MC predictions without any corrections are shown for the b-veto tail region ($\met > 100 \GeV$ and $ \mt > 150 \GeV$) . |
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\label{tab:bvetoyieldtail}} |
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\end{center} |
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\end{table} |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{c|c} |
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\hline |
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\hline |
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\end{tabular} |
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\caption{ Raw Data and MC predictions without any corrections are shown after preselection and b-tagging. |
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\label{tab:btagpreselection}} |
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\end{center} |
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\end{table} |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{c|c} |
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\hline |
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\hline |
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\end{tabular} |
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\caption{ Raw Data and MC predictions without any corrections are shown for the peak region after b-tagging but before applying the isolated track veto. |
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This region is used to normalize the top bkg prediction from MC to data. |
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\label{tab:btagpeakregionnotrkiso}} |
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\end{center} |
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\end{table} |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{c|c} |
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\hline |
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\hline |
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\end{tabular} |
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\caption{ Raw Data and MC predictions without any corrections are shown for the tail region after b-tagging and isolated track veto are applied. |
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As this is our signal region, only MC yields are shown at this point. |
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\label{tab:btagtailaftertrkiso}} |
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\end{center} |
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\end{table} |
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|
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\subsection{Dilepton control region} |
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|
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We define a dilepton control region requiring two isolated leptons, $ee, e\mu$, or $\mu\mu$ to study the jet multiplicity in data and MC, and derive |
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scale factors based on their consistency. This study is documented in Section~\ref{sec:jetmultiplicity}. |
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|
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In this region we require: |
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\begin{itemize} |
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\item dilepton triggers |
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\item two leptons with $\pt > 20 \GeV$ that pass our lepton id and isolation |
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\item $\met > 50 \GeV$ |
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\item $\ge 1$ b-tag, SSV medium |
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\end{itemize} |
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|
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This sample is only partially overlapping with the single lepton preselection as it requires the dilepton rather than the single lepton triggers, and |
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differs in the $\pt$ requirement for the leading lepton. Table~\ref{tab:dileptonyield} shows the raw yields in data and MC prior to any corrections. |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{c|c} |
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\hline |
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\hline |
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\end{tabular} |
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\caption{ Raw Data and MC predictions without any corrections are shown for the dilepton control region. |
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This region is used for correcting the jet multiplicity seen in MC to that in data. |
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\label{tab:dileptonyield}} |
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\end{center} |
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\end{table} |
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|
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\subsection{Corrections to Jets and \met} |
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|
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data (MC). In addition, these jet energy corrections are propagated to |
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the \met\ calculation, following the official prescription for |
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deriving the Type I corrections. It may be noted that events with |
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anomalous corrections are excluded from the sample since these |
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anomalous ``rho'' pile-up corrections are excluded from the sample since these |
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correspond to events with unphysically large \met\ and \mt\ tail |
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signal region. An additional correction to remove |
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signal region (see Figure~\ref{fig:mtrhocomp}). An additional correction to remove |
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the $\phi$-modulation observed in the \met\ is included, improving |
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the agreement between the data and the MC, as shown in |
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Figure.~\ref{fig:metphicomp}. This correction has an effect on this analysis, |
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Figure~\ref{fig:metphicomp}. This correction has an effect on this analysis, |
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since the azimuthal angle enters the \mt\ distribution. |
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|
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\begin{figure}[tbh] |
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\clearpage |
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|
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\begin{figure}[!ht] |
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\begin{center} |
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\includegraphics[width=0.5\linewidth]{plots/mt_rho_comp.png} |
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\caption{ \label{fig:mtrhocomp}%\protect |
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\end{center} |
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\end{figure} |
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|
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\begin{figure}[hb] |
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\begin{figure}[!hb] |
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\begin{center} |
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\includegraphics[width=0.5\linewidth]{plots/metphi.pdf}% |
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\includegraphics[width=0.5\linewidth]{plots/metphi_phicorr.pdf} |
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\end{center} |
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\end{figure} |
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|
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\clearpage |
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|
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\subsection{Branching Fraction Correction} |
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|
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The leptonic branching fraction used in some of the \ttbar\ MC samples |
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differs from the value listed in the PDG $(10.80 ± 0.09)\%$. |
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differs from the value listed in the PDG $(10.80 \pm 0.09)\%$. |
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Table.~\ref{tab:wlepbf} summarizes the branching fractions used in |
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the generation of the various \ttbar\ MC samples. |
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For \ttbar\ samples with the incorrect leptonic branching fraction, event |
