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\section{Event Preselection} |
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\label{sec:eventSel} |
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%{\color{red} This needs to be fixed up -- probably many mistakes present.}\\ |
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As mentioned in the introduction, the preselection is based on the |
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$t\bar{t}$ analysis. We select events with two opposite sign isolated |
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The purpose of the preselection is to define a data sample rich |
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in $t\bar{t} \to$ dileptons. We compare the kinematical |
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properties of this sample with expectations from $t\bar{t}$ |
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Monte Carlo. |
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The preselection is based on the |
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$t\bar{t}$ analysis~\cite{ref:top}. |
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We select events with two opposite sign isolated |
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leptons ($ee$, $e\mu$, or $\mu\mu$); one of the leptons must |
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have $P_T > 20$ GeV, |
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the other one must have $P_T > 10$ GeV\footnote{In case of events with |
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the other one must have $P_T > 10$ GeV. Events consistent with $Z$ are rejected. |
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In case of events with |
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more than two such leptons, we select the pair that maximizes the scalar |
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sum of lepton $P_T$'s.}; |
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there must be two JPT |
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sum of lepton $P_T$'s. |
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There must be two JPT |
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jets of $P_T > 30$ GeV and $|\eta| < 2.5$; the scalar sum of the |
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$P_T$ of all such jets must exceed 100 GeV; jets must pass |
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{\tt caloJetId} and be separated by $\Delta R >$ 0.4 from the |
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two leptons. Finally $\met > 50$ GeV |
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(we use tcMet). More details are given in the subsections below. |
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{\tt caloJetId} and be separated by $\Delta R >$ 0.4 from any |
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lepton passing the selection. |
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Finally $\met > 50$ GeV (we use tcMet). More details are given in the subsections below. |
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\subsection{Event Cleanup} |
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\label{sec:cleanup} |
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It is motivated by the observation of |
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poorly measured muons in data with large |
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relative $P_T$ uncertainty, giving significant contributions to the \met. |
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%{\color{red} This is not applied to the 11 pb iteration.} |
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\end{itemize} |
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\begin{itemize} |
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\item $P_T > 10$ GeV. (The $t\bar{t}$ analysis uses 20 GeV but for |
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completeness we calculate FR down to 10 GeV). |
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% \item $P_T > 10$ GeV. (The $t\bar{t}$ analysis uses 20 GeV but for |
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% completeness we calculate FR down to 10 GeV). |
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\item $|\eta| < 2.5$. |
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We remove $e^+e^-$ and $\mu^+ \mu^-$ events with invariant |
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mass between 76 and 106 GeV. We also remove events |
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with invariant mass $<$ 10 GeV. |
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with invariant mass $<$ 10 GeV, since this kinematical region is |
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not well reprodced in CMS Monte Carlos. |
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In addition, we remove $Z \to \mu\mu\gamma$ |
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candidates with the $\gamma$ collinear with one of the muons. This is |
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done as follows: |
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if the ecal energy associated with one of the muons is greater than 6 GeV, |
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we add this energy to the momentum of the initial muon, and we recompute |
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the $\mu\mu$ mass. If this mass is between 76 and 106 GeV, the event is rejected. |
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\subsection{Trigger Selection} |
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\label{sec:trigSel} |
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Because most of the triggers implemented in the 2nd half of the |
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2010 run were not implemented in the Monte Carlo, no trigger |
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selection is applied on Monte Carlo data. As discussed in |
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2010 run were not implemented in the Monte Carlo, |
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we do not make any requirements on HLT bits in the Monte Carlo. |
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Instead, as discussed in |
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Section~\ref{sec:trgEff}, a trigger efficiency weight is applied |
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to each event, based on the trigger efficiencies measured on data. |
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Trigger efficiency weights are very close to 1. |
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% We currently |
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% do not require MC events to pass any triggers. |
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\begin{itemize} |
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\item single-muon triggers |
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\begin{itemize} |
