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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 Selection} |
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[UPDATE SELECTION] |
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|
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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}). Dilepton triggers are used only for the dilepton control region. |
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Table.~\ref{tab:DatasetsData}). |
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Note that the analysis triggers are inclusive single lepton triggers. |
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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 $\pt>30~\GeVc$ and $|\eta|<2.1$ |
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\item satisfy the identification and isolation requirements detailed |
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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. |
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within $|\eta|<2.5$ out of which at least 1 satisfies the CSV |
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medium working point b-tagging requirement |
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\item require moderate $\met>50~\GeV$ |
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\end{itemize} |
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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, especialy 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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Table~\ref{tab:preselectionyield} shows the yields in data and MC without any corrections for this preselection region. |
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A benchmark signal region is selected by tightening the \met\ and |
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adding an \mt\ as well as isolated track veto requirement |
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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 isolated track veto as discussed below |
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\end{itemize} |
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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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\subsection{Signal Region Selection} |
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|
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[MOTIVATIONAL BLURB ON MET AND MT, \\ |
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CAN ADD SIGNAL VS. TTBAR MC PLOT \\ |
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ADD SIGNAL YIELDS FOR AVAILABLE POINTS, \\ |
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DISCUSS CHOICE SIG REGIONS] |
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|
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The signal regions (SRs) are selected to improve the sensitivity for the |
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single lepton requirements and cover a range of scalar top |
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scenarios. The \mt\ and \met\ variables are used to define the signal |
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regions and the requirements are listed in Table~\ref{tab:srdef}. |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{l|c|c} |
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\hline |
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Signal Region & Minimum \mt\ [GeV] & Minimum \met\ [GeV] \\ |
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\hline |
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\hline |
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SRA & 150 & 100 \\ |
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SRB & 120 & 150 \\ |
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SRC & 120 & 200 \\ |
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SRD & 120 & 250 \\ |
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SRE & 120 & 300 \\ |
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\hline |
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\end{tabular} |
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\caption{ Signal region definitions based on \mt\ and \met\ |
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requirements. These requirements are applied in addition to the |
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baseline single lepton selection. |
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\label{tab:srdef}} |
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\end{center} |
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\end{table} |
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|
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Table~\ref{tab:srrawmcyields} shows the expected number of SM |
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background yields for the SRs. A few stop signal yields for four |
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values of the parameters are also shown for comparison. The signal |
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regions with looser requirements are sensitive to lower stop masses |
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M(\sctop), while those with tighter requirements are more sensitive to |
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higher M(\sctop). |
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|
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\begin{table}[!h] |
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\begin{center} |
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\begin{tabular}{l||c|c|c|c} |
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\hline |
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Sample & SRA & SRB & SRC & SRD \\ |
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\hline |
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\hline |
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\ttdl\ & $700 \pm 15$& $408 \pm 12$& $134 \pm 7$& $43 \pm 4$ \\ |
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\ttsl\ \& single top (1\Lep) & $111 \pm 6$& $71 \pm 5$& $15 \pm 2$& $4 \pm 1$ \\ |
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\wjets\ & $58 \pm 35$& $57 \pm 35$& $29 \pm 26$& $26 \pm 26$ \\ |
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Rare & $63 \pm 3$& $40 \pm 3$& $17 \pm 2$& $7 \pm 1$ \\ |
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\hline |
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Total & $932 \pm 39$& $576 \pm 38$& $195 \pm 27$& $80 \pm 26$ \\ |
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\hline |
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\end{tabular} |
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\caption{ Expected SM background contributions, including both muon |
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and electron channels. This is ``dead reckoning'' MC with no |
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correction. |
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It is meant only as a general guide. The uncertainties are statistical only. ADD |
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SIGNAL POINTS. |
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\label{tab:srrawmcyields}} |
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\end{center} |
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\end{table} |
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|
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\subsection{Control Region Selection} |
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|
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[1 PARAGRAPH BLURB RELATING BACKGROUNDS (IN TABLE FROM PREVIOUS SECTION) |
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TO INTRODUCE CONTROL REGIONS] |
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|
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Control regions (CRs) are used to validate the background estimation |
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procedure and derive systematic uncertainties for some |
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contributions. The CRs are selected to have similar |
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kinematics to the SRs, but have a different requirement in terms of |
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number of b-tags and number of leptons, thus enhancing them in |
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different SM contributions. The four CRs used in this analysis are |
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summarized in Table~\ref{tab:crdef}. |
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|
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\begin{table} |
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\begin{center} |
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{\small |
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\begin{tabular}{l|c|c|c} |
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\hline |
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Selection & \multirow{2}{*}{exactly 1 lepton} & \multirow{2}{*}{exactly 2 |
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leptons} & \multirow{2}{*}{1 lepton + isolated |
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track}\\ |
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Criteria & & & \\ |
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\hline |
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\hline |
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\multirow{4}{*}{0 b-tags} |
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& CR1) W+Jets dominated: |
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& CR2) apply \Z-mass constraint |
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& CR3) not used \\ |
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& |
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& $\rightarrow$ Z+Jets dominated: Validate |
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& \\ |
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& Validate W+Jets \mt\ tail |
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& \ttsl\ \mt\ tail comparing |
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& \\ |
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& |
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& data vs. MC ``pseudo-\mt '' |
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& \\ |
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\hline |
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\multirow{4}{*}{$\ge$ 1 b-tags} |
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& |
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& CR4) Apply \Z-mass veto |
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& CR5) \ttdl, \ttlt\ and \\ |
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& SIGNAL |
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& $\rightarrow$ \ttdl\ dominated: Validate |
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& \ttlf\ dominated: Validate \\ |
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& REGION |
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& ``physics'' modelling of \ttdl\ |
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& \Tau\ and fake lepton modeling/\\ |
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& |
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& |
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& detector effects in \ttdl\ \\ |
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\hline |
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\end{tabular} |
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} |
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\caption{Summary of signal and control regions. |
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\label{tab:crdef}%\protect |
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} |
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\end{center} |
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\end{table} |
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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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\subsection{Corrections to Jets and \met} |
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\subsection{MC Corrections} |
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|
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[UPDATE SECTION] |
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|
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\subsubsection{Corrections to Jets and \met} |
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[UPDATE, ADD FEW MORE DETAILS ON WHAT IS DONE HERE] |
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The official recommendations from the Jet/MET group are used for |
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the data and MC samples. In particular, the jet |
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based on the global tags GR\_R\_42\_V23 (DESIGN42\_V17) for |
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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 ``rho'' pile-up corrections are excluded from the sample since these |
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deriving the Type I corrections. |
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|
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Events with 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 (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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since the azimuthal angle enters the \mt\ distribution. |
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|
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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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Comparison of the \mt\ distribution for events with |
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unphysical energy corrections ($\rho <0$ or $ \rho > 40$, where $\rho$ is a |
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measure of the average pileup energy density) and the |
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nominal sample. Events with large pileup corrections |
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correspond to noisy events. Since this correction is applied |
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to the jets and propagated to the \met, these events have |
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anomalously large \met\ and populate the \mt\ tail. These |
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pathological events are excluded from the analysis sample.} |
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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{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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\caption{ \label{fig:metphicomp}%\protect |
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The PF \met\ $\phi$ distribution (left) exhibits a |
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modulation. After applying a dedicated correction, the |
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azimuthal dependence is reduced (right).} |
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\end{center} |
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\end{figure} |
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signal region. In addition, the recommended MET filters are applied. |
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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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\subsubsection{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 $(10.80 \pm 0.09)\%$. |
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\end{center} |
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\end{table} |
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|
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|
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\subsubsection{Efficiency Corrections} |
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|
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[TO BE UDPATED WITH T\&P STUDIES ON ID, TRIGGER ETC] |
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|
