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\section{Event reconstruction} |
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\label{sec:eventReconstruction} |
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The four possible final states of \WZ |
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production with electrons and muons are studied, $\rm e^\pm \epem$, $\mu^\pm \epem$, $\rm e^\pm \mu^+\mu^-$ |
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and $\mu^\pm \mu^+\mu^-$. They are associated to four possible classes, |
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denoted as follows: |
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We categorize \WZ\ three-lepton final state as following |
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\begin{itemize} |
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\item $3e$: for \WZ events with $\W \to e \nu$ and $\Z\to \epem$. |
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\item $2e1\mu$: for \WZ events with $\W \to \mu \nu$ and $\Z\to \epem$. |
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\subsection{Trigger selection and efficiencies} |
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Events stemming from the three-lepton final states of $\WZ$ production |
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are collected by the electron and muon triggers. For each channel, |
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are collected by the electron and/or muon triggers. For each channel, |
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a minimun number of HLT requirements is chosen while keeping |
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the HLT efficiency for selected events close to 100\%. The same |
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HLT requirements are used for channels with the same Z decay mode: |
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HLT requirements are used for channels with the same \Z decay mode: |
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\begin{itemize} |
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\item for $3e$ and $2e1\mu$: HLTSingleElectron or HLTDoubleElectronRelaxed |
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\item for $2\mu1e$ and $3\mu$: HLTSingleMuonIso |
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The HLT efficiencies for all modes for events passing the full |
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selection described in this section are given in table~\ref{tab:hlteff}. |
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– |
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\begin{table}[tbph] |
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\begin{center} |
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|
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\end{tabular} |
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\end{center} |
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\caption{HLT Efficiencies, in percent, for all |
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the events in the generated phase space for events retained by |
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the complete event selection.} |
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\caption{HLT Efficiencies for all the events in the generated phase space that |
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have been retained by the complete event selection.} |
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\label{tab:hlteff} |
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\end{table} |
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|
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\begin{figure}[tbp] |
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\begin{center} |
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\scalebox{0.7}{\includegraphics{figs/mu_isol.eps}} |
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\caption{Muon isolation variables for the muon associated |
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to the \W boson decay in $2e1\mu$ events: in the left plot |
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we illustrate the sum of calorimetric energy in a $\Delta R=0.3$ cone |
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around the muon candidate; in the right plot we display the sum of |
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transverse momenta of tracks within a $\Delta R = 0.25$ cone around |
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the muon candidate. The normalization of signal and background |
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distributions is arbitrary. |
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} |
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\label{fig:mu_isol} |
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\end{center} |
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\end{figure} |
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|
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\begin{figure}[tb] |
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\begin{center} |
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\scalebox{0.6}{\includegraphics{figs/mu_SIP.eps}} |
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\caption{ |
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Muon impact parameter significance distribution |
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in $2e1\mu$ events. The normalization of signal and background |
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distributions is arbitrary. |
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} |
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\label{fig:mu_SIP} |
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\end{center} |
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\end{figure} |
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|
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|
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\subsection{Lepton identification} |
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\label{sec:leptonId} |
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in~\cite{noteElectronID}. |
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Muon candidates are selected from global muons, which are reconstructed |
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combining measurements in the muon chambers and the central tracker. |
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An additional isolation criterion requires that the energy |
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by combining measurements in the muon chambers and the central tracker. |
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An additional isolation criterion is imposed to require the energy |
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measured in the calorimeters within a $\Delta R = 0.3$ cone around the |
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muon must be smaller than 3 GeV and the sum of the $p_t$ of tracks |
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within a $\Delta R = 0.35$ cone around the muon must be smaller than 2.5 |
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GeV. These cuts reduce the background from muons originated in |
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muon to be smaller than 3 GeV and the sum of the $p_T$ of tracks |
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within a $\Delta R = 0.25$ cone around the muon must be smaller than 2 GeV. |
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These cuts reduce the background from muons originated in |
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\b-quark decays of the $\Zbbbar$ background, which are close to tracks |
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and clusters from the other \b-quark decay products. |
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The signal and background distributions of these isolation variables |
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are shown in Figure~\ref{fig:mu_isol} for the muon in $2e1\mu$ candidate |
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events. |
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|
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%Figures~\ref{fig:muonisol} and ~\ref{fig:muonisoleffi} show the |
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%performance of the isolation cut. The distribution of the isolation |
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%variables for the $\Z\b\bbar(\epem\b\bbar)$ is particularly |
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%interesting, since muons only stem from \b-quark decays. |
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The significance of the muon impact parameter in the plane |
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transverse to the beam, $S_{IP}$, discriminates against leptons from |
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heavy-quark decays in all standard model background processes. This |
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variable is defined as the ratio between the measured impact parameter |
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and its uncertainty: $S_{IP}=IP/\sigma_{IP}$, and is required to |
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satisfy $S_{IP}<3$. This requirement is applied only for muon candidates |
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and not for electrons. For electron candidates, a significant fraction of the |
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background comes from misidentified light quark jets. Thus, |
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the requirement on the impact parameter significance does not |
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increase the significance of the $\W\to e$ channels, as can be seen in |
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Fig.~\ref{fig:wl_IP_SvsCut}. The distribution of $S_{IP}$ for the muon |
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in $2e1\mu$ candidate events is shown in Figure~\ref{fig:mu_SIP}. |
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|
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\begin{figure}[p] |
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\begin{center} |
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\scalebox{0.6}{\includegraphics{figs/wl_IP_eff.eps}} |
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\caption{Efficiency for signal and background as a function |
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of the requirement on the \W-boson lepton impact parameter |
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significance. All other criteria but the one on impact parameter |
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significance are applied. |
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% Only events with 81 GeV $< M_Z < $ 101 \gev |
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% are considered. |
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} |
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\label{fig:wl_IP_eff} |
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\end{center} |
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%\end{figure} |
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|
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%\begin{figure}[bt] |
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\begin{center} |
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\scalebox{0.6}{\includegraphics{figs/wl_IP_SvsCut.eps}} |
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\caption{Signal significance as a function of requirement on |
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the \W-boson lepton impact parameter significance. All other criteria but |
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the requirement on the impact parameter significance are applied. |
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% Only events with 81 GeV $< M_Z < $ 101 \gev are considered. |
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} |
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\label{fig:wl_IP_SvsCut} |
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\end{center} |
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\end{figure} |
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|
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|
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\begin{table}[tbp] |
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\begin{tabular}{|l|c|c|c|c|} \hline |
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& $3e$ & $2e1\mu$ & $2\mu 1e$ & $3\mu$ \\ \hline \hline |
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\multicolumn{5}{|c|}{Lepton selection} \\ \hline |
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Electrons & \multicolumn{3}{|c|}{{\tt SimpleLoose} requirements for \Z reconstruction} & \\ |
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& \multicolumn{3}{|c|}{{\tt SimpleTight} requirements for \W} & \\ \hline |
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Muons & & \multicolumn{3}{|c|}{ Track Isolation:$ {\tt IsoTrack}(\Delta R= 0.25) < 2 \gev$} \\ |
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& & \multicolumn{3}{|c|}{ Calorimetric Isolation:$ {\tt IsoCalo}(\Delta R = 0.3) < 5 \gev$} \\ |
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& & \multicolumn{3}{|c|}{$S_{IP}=IP/\sigma_{IP}<3$ } \\ \hline |
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HLT requirement & \multicolumn{2}{|c|}{ HLTSingleElectron or HLTDoubleElectronRelaxed} |
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& \multicolumn{2}{|c|}{ HLTSingleMuonIso} \\ \hline |
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\multicolumn{5}{|c|}{\Z reconstruction} \\ \hline |
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Lepton cuts & \multicolumn{4}{|c|}{for both \Z leptons: $p_T > 15$ GeV} \\ |
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Mass window & \multicolumn{4}{|c|}{$50 \gev < M_Z < 120 \gev $ } \\ |
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Second \Z veto & \multicolumn{4}{|c|}{No independent second \Z candidate with $50 \gev < M_Z < 120 \gev $ } \\ \hline |
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\multicolumn{5}{|c|}{\W lepton selection} \\ \hline |
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|
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Other cuts & & & $\Delta R(\mu_Z,e_W)>0.1$ & \\ \hline |
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Signal region & \multicolumn{4}{|c|}{$81 \gev < M_Z < 101 \gev $ } \\ \hline \hline |
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|
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\end{tabular} |
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\caption{Summary of the criteria we use to select \WZ\ final state} |
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\label{tab:allcuts} |
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\end{table} |
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|
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|
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\begin{figure}[p] |
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\begin{center} |
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\scalebox{0.6}{\includegraphics{figs/wlpt_cuteff.eps}} |
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\caption{Efficiency for signal and background as a function |
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of the cut value on the \W-boson lepton transverse momentum. |
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All other cuts but the cut on this variable are applied. |
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Only events with 81 GeV $< M_Z < $ 101 \gev |
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are considered.} |
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\label{fig:wlpt_cuteff} |
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\end{center} |
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%\end{figure} |
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|
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%\begin{figure}[bt] |
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\begin{center} |
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\scalebox{0.6}{\includegraphics{figs/wlpt_cutS.eps}} |
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\caption{Signal significance as a function of the cut value on |
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the \W-boson lepton transverse momentum. All other cuts but |
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the cut on this variable are applied. Only events with |
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81 GeV $< M_Z < $ 101 \gev are considered.} |
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\label{fig:wlpt_cutS} |
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\end{center} |
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\end{figure} |
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|
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|
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\subsection{\WZ candidate selection} |
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Events are accepted if they contain at least three charged leptons, |
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either electrons or muons, with $p_t > 10\,\mathrm{GeV}$ and $| \eta | < 2.5$, as |
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discussed in~\ref{sec:leptonId}. |
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either electrons or muons, with $p_T > 15\,\mathrm{GeV}$ and $| \eta | < 2.5$ for |
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electrons,$| \eta | < 2.4$ for muons, as discussed in Section~\ref{sec:leptonId}. |
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|
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The \WZ candidate selection proceeds from building all possible |
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\Z-boson candidates from same-flavour opposite-charge lepton pairs. |
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For $\Z \to ee$ decays, electrons have to fullfil the loose requirements |
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For $\Z \to ee$ decays, electron candidates have to fulfill the loose requirements |
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defined in~\cite{noteElectronID}. |
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Events are retained if the mass of this \Z-boson candidate is |
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within 20 GeV of the Z-boson mass,$m_Z$. The event is |
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rejected if a second Z candidate is found. This second Z candidate is done |
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with all possible same-flavour opposite-charge combinations which are left |
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after removing the two leptons already used for the first Z candidate. This |
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veto on the presence of a second Z helps to suppress $ZZ$ events. The invariant |
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mass distribution for accepted \Z candidates is shown in |
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Figure~\ref{fig:zcandidates}. |
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Events are retained if the mass of the \Z boson candidate is |
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within 20 GeV of the \Z boson mass, $m_Z$. The event is |
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rejected if a second \Z candidate is found. This second \Z boson candidate is formed |
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using all possible same-flavour opposite-charge combinations which are left |
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after removing the two leptons already used for the first \Z boson candidate. This |
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secondary \Z boson veto helps to suppress $\Z\Z$ events. |
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%The invariant |
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%mass distribution for accepted \Z candidates is shown in |
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%Figure~\ref{fig:zcandidates}. |
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% and the \Z mass resolution is shown in |
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%Figure~\ref{fig:dzmass}. |
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After the \Z-boson candidate is identified, the lepton associated |
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to the \W-boson decay is chosen from the remaining electrons and muons |
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in the event that have not been used for reconstructing the \Z-boson. |
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Electrons are required to pass the tight criteria described in |
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\cite{noteElectronID}. If the event contains more than three leptons, |
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the highest $p_t$ is chosen as the one from the \W-boson decay, and |
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the additional leptons are not considered further. |
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The transverse momentum of this lepton is required to be larger |
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than 20 GeV. This last requirement is effective in rejecting |
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the \Zbbbar and \Zjets backgrounds, and the cut value is chosen in |
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the range that maximises the significance as shown in |
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Figure~\ref{fig:s_vs_wlpt}. |
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|
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|
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The expected number of events passing the various steps of the selection |
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is listed in Tables~\ref{tab:sel-effA} and~\ref{tab:sel-effB}. |
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Table~\ref{tab:wz-effimatrix} lists the final selection efficiency for |
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the different generated \W and \Z decays. It can be seen there that \WZ\ |
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events with both the \W and the \Z boson decaying into electrons or muons |
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almost always get reconstructed with the correct flavour. It is to be |
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noted in addition that each of our four selection channels gets a small |
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contribution from $W \to \tau \to e/\mu$ decays as one would expect. The |
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selection efficiency for these events is however smaller which is mostly due |
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to the \pt cut on the third lepton, since the \pt spectrum of electrons or |
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muons from $W \to \tau \to e/\mu$ decays is softer. |
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After the \Z boson candidate is identified, the remaining leptons in the event |
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are required, for electrons, to pass the tight criteria described in~\cite{noteElectronID} |
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or, for muons, all criteria described in section~\ref{sec:leptonId}. |
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If more than one lepton candidate satisfies the tight requirements, the one with the |
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highest $p_T$ is associated with \W boson decay. This lepton's $p_T$ is effective |
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discriminant against \Zbbbar and \Zjets production (see Fig.~\ref{fig:wlpt_cuteff}). |
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We require the transverse momentum to exceed 20 GeV, as it maximizes |
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the significance of the \WZ\ signal with respect to background as shown in |
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Fig.~\ref{fig:wlpt_cutS}. |
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|
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An additional requirement on the isolation between electron and muon candidates is applied |
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for the $2\mu 1e$ channel, by demanding the value of $\Delta R$ between the electron |
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candidate associated with the \W boson decay and any of the two muons associated with |
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the \Z boson decay to be greater than 0.1. |
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|
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This requirement allows suppressing the contribution of $\Z \to \mu\mu$ |
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decays, where one of the two muons radiates a photon which is reconstructed |
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as an electron, possibly after conversion. This can be seen as a peak in the dimuon |
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invariant mass at around 60 GeV in Fig.~\ref{fig:Z2mu1e_60GeVPeak}. |
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|
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The summary of the selection criteria is given in Table~\ref{tab:allcuts}. |
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|
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The expected number of the events satisfying the sequential steps of the selection |
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is listed in Tables~\ref{tab:sel-effA}. |
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In Table~\ref{tab:wz-effimatrix} we list the total selection efficiency for different |
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\W and \Z boson decay modes. It can be seen lepton candidates from \W and \Z |
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boson decays are almost always are reconstructed with the correct flavor. As expected, |
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there is a small contribution from $\W \to \tau \nu_\tau \to \ell \nu_\ell \nu_\tau$ |
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decays. However, this contribution is suppressed, mostly due to $p_T$ requirement |
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on the third lepton, as leptons from $\tau$ decays are not as energetic as those from |
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$\W \to \ell \nu$ processes. |
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|
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In Tables~\ref{tab:wz-matcheffi-Zee} and \ref{tab:wz-matcheffi-Zmumu} we |
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display the fraction of reconstructed \WZ events with correctly-matched leptons. |
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It can be seen that the lepton associated with the \W boson decay is correctly matched |
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to the true Monte Carlo lepton from the \W boson decay in more than 90\% of |
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the cases, even for events with several lepton candidates available to be associated |
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to the \W boson decay. The choice to take the lepton candidate with the leading $p_T$ is, |
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therefore, justified. |
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|
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\begin{table}[p] |
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\begin{center} |
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|
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\begin{tabular}{lcc|cc|cc|cc|} \hline |
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\multicolumn{9}{c}{ {\bf $3e$ Channel}} \\ \hline \hline |
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Step & $\WZ \to 3e\nu$ & $ \epsilon$ & $\Z+jets$ & $ \epsilon$ & $t\bar{t}+jets$ & $ \epsilon$ & $b\bar{b}\ell\ell$ & $ \epsilon$\\ \hline |
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All events & 185 & & $5.82\cdot 10^6$ & & $8.27\cdot 10^5$ & & $1.44\cdot 10^5$ & \\ |
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Found $\Z \to ee$ & 73.9 & 39.9\% & $5.02\cdot 10^5$ & 8.63\% & $2.92\cdot 10^3$ & 0.353\% & $2.78\cdot 10^4$ & 19.4\% \\ |
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Second \Z veto & 73.9 & 100\% & $5.02\cdot 10^5$ & 100\% & $2.92\cdot 10^3$ & 99.9\% & $2.78\cdot 10^4$ & 100\% \\ |
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Found $\W \to e\nu$ & 37.4 & 50.6\% & 310 & 0.062\% & 13.8 & 0.474\% & 171 & 0.61\% \\ |
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\W lepton $p_T$ cut & 32.5 & 86.7\% & 86.8 & 28\% & 8.26 & 59.7\% & 23.4 & 13.7\% \\ |
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Passes HLT & 32.3 & 99.6\% & 86.8 & 100\% & 8.26 & 100\% & 23.3 & 99.7\% \\ |
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\Z mass window & 29.5 & 91.2\% & 51.9 & 59.8\% & 3.26 & 39.5\% & 17.3 & 74\% \\ |
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\hline |
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Overall efficiency & & 15.9\% & & 0.00089\% & & 0.00039\% & & 0.012\% \\ |
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\hline |
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|
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\multicolumn{9}{c}{ {\bf $2e1\mu$ Channel}} \\ \hline \hline |
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Step & $\WZ \to 2e1\mu\nu$ & $ \epsilon$ & $\Z+jets$ & $ \epsilon$ & $t\bar{t}+jets$ & $ \epsilon$ & $b\bar{t}\ell\ell$ & $ \epsilon$\\ \hline |
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All events & 185 & & $5.82\cdot 10^6$ & & $8.27\cdot 10^5$ & & $1.44\cdot 10^5$ & \\ |
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Found $\Z \to ee$ & 63.8 & 34.5\% & $5.02\cdot 10^5$ & 8.63\% & $2.92\cdot 10^3$ & 0.35\% & $2.78\cdot 10^4$ & 19.4\% \\ |
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Second \Z veto & 63.7 & 99.9\% & $5.02\cdot 10^5$ & 100\% & $2.92\cdot 10^3$ & 99.9\% & $2.78\cdot 10^4$ & 100\% \\ |
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Found $\W \to \mu\nu$ & 42.6 & 66.8\% & $2.19\cdot 10^3$ & 0.44\% & 55.6 & 1.91\% & 748 & 2.69\% \\ |
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> |
\W lepton $p_T$ cut & 35.1 & 82.5\% & 9.58 & 0.44\% & 16.4 & 29.5\% & 9.49 & 1.27\% \\ |
| 275 |
> |
Passes HLT & 34.3 & 97.6\% & 8.32 & 86.9\% & 14.1 & 86\% & 9.12 & 96.1\% \\ |
| 276 |
> |
\Z mass window & 30.8 & 89.8\% & 7.31 & 87.9\% & 3.76 & 26.7\% & 8 & 87.8\% \\ |
| 277 |
> |
\hline |
| 278 |
> |
Overall efficiency & & 16.7\% & & 0.00013\% & & 0.00045\% & & 0.0056\% \\ |
| 279 |
> |
\hline |
| 280 |
> |
|
| 281 |
> |
\multicolumn{9}{c}{ {\bf $2\mu1e$ Channel}} \\ \hline \hline |
| 282 |
> |
Step & $\WZ \to 2\mu1e$ & $ \epsilon$ & $\Z+jets$ & $ \epsilon$ & $t\bar{t}+jets$ & $ \epsilon$ & $b\bar{b}\ell\ell$ & $ \epsilon$\\ \hline |
| 283 |
> |
All events & 190 & & $5.82\cdot 10^6$ & & $8.27\cdot 10^5$ & & $1.44\cdot 10^5$ & \\ |
| 284 |
> |
Found $\Z \to \mu\mu$ & 75.2 & 39.7\% & $5.77\cdot 10^5$ & 9.92\% & $2.78\cdot 10^3$ & 0.336\% & $3.19\cdot 10^4$ & 22.2\% \\ |
| 285 |
> |
Second \Z veto & 75.2 & 100\% & $5.77\cdot 10^5$ & 100\% & $2.77\cdot 10^3$ & 99.9\% & $3.19\cdot 10^4$ & 100\% \\ |
| 286 |
> |
Found $\W \to e\nu$ & 44 & 58.5\% & 702 & 0.12\% & 15.1 & 0.54\% & 213 & 0.67\% \\ |
| 287 |
> |
\W lepton $p_T$ cut & 38.4 & 87.2\% & 464 & 66.2\% & 10.3 & 68\% & 50.5 & 23.7\% \\ |
| 288 |
> |
$\Delta R(e,\mu)$ cut & 38.4 & 99.9\% & 93 & 20\% & 7.15 & 69.6\% & 23.3 & 46\% \\ |
| 289 |
> |
Passes HLT & 37.3 & 97.1\% & 88.8 & 95.5\% & 6.62 & 92.7\% & 23.1 & 99.4\% \\ |
| 290 |
> |
\Z mass window & 33.6 & 90.1\% & 50.3 & 56.6\% & 2.84 & 42.9\% & 18.8 & 81.4\% \\ |
| 291 |
> |
\hline |
| 292 |
> |
Overall efficiency & & 17.7\% & & 0.00086\% & & 0.00034\% & & 0.013\% \\ |
| 293 |
> |
\hline |
| 294 |
> |
%\end{tabular} |
| 295 |
> |
%\begin{tabular}{lcc|cc|cc|cc|} \hline |
| 296 |
> |
\multicolumn{9}{c}{ {\bf $3\mu$ Channel}} \\ \hline \hline |
| 297 |
> |
Step & $\WZ \to 3\mu$ & $ \epsilon$ & $\Z+jets$ & $ \epsilon$ & $t\bar{t}+jets$ & $ \epsilon$ & $b\bar{b}\ell\ell$ & $ \epsilon$\\ \hline |
| 298 |
> |
All events & 189 & & $5.82\cdot 10^6$ & & $8.27\cdot 10^5$ & & $1.44\cdot 10^5$ & \\ |
| 299 |
> |
Found $\Z \to \mu\mu$ & 83.8 & 44.3\% & $5.77\cdot 10^5$ & 9.92\% & $2.78\cdot 10^3$ & 0.336\% & $3.19\cdot 10^4$ & 22.2\% \\ |
| 300 |
> |
Second \Z veto & 83.6 & 99.8\% & $5.77\cdot 10^5$ & 100\% & $2.77\cdot 10^3$ & 99.9\% & $3.19\cdot 10^4$ & 100\% \\ |
| 301 |
> |
Found $\W \to \mu\nu$ & 51.8 & 62\% & $2.52\cdot 10^3$ & 0.44\% & 34.8 & 1.25\% & 810 & 2.54\% \\ |
| 302 |
> |
\W lepton $p_T$ cut & 42.5 & 81.9\% & 1.84 & 0.07\% & 1.16 & 3.33\% & 8.89 & 1.1\% \\ |
| 303 |
> |
Passes HLT & 42.2 & 99.4\% & 1.84 & 100\% & 1.16 & 100\% & 8.89 & 100\% \\ |
| 304 |
> |
\Z mass window & 38.5 & 91.1\% & 1.84 & 100\% & 1.16 & 100\% & 7.78 & 87.5\% \\ |
| 305 |
> |
\hline |
| 306 |
> |
Overall efficiency & & 20.3\% & & 0.000032\% & & 0.00014\% & & 0.0054\% \\ |
| 307 |
> |
\hline |
| 308 |
> |
\end{tabular} |
| 309 |
> |
|
| 310 |
> |
\caption{Expected number of signal and background events passing the different |
| 311 |
> |
selections steps together with the efficiency of each requirement and total efficiency of |
| 312 |
> |
selection criteria in the \WZ, \Zbbbar, \Zjets and \ttjets samples for an integrated luminosity |
| 313 |
> |
of 1 \invfb.} |
| 314 |
> |
\label{tab:sel-effA} |
| 315 |
> |
\end{center} |
| 316 |
> |
\end{table} |
| 317 |
> |
|
| 318 |
> |
\begin{table}[p] |
| 319 |
> |
\begin{center} |
| 320 |
> |
\begin{tabular}{l|ccccc} |
| 321 |
> |
\hline \hline |
| 322 |
> |
& \multicolumn{5}{c}{$\Z \to ee$ and \W decay modes below} \\ |
| 323 |
> |
Reconstruction channel & $e \nu$ |
| 324 |
> |
& $\mu \nu $ |
| 325 |
> |
& $\tau \nu \to e \nu \nu $ |
| 326 |
> |
& $\tau \nu \to \mu \nu \nu $ |
| 327 |
> |
& $\tau \nu \to {\rm hadrons~} \nu$ |
| 328 |
> |
\\ \hline |
| 329 |
> |
$3e$ & 17.4\% & 0.0319\% & 6.42\% & 0\% & 0.162\% \\ |
| 330 |
> |
$2e1\mu$ & 0\% & 18.6\% & 0\% & 5.53\% & 0.0485\% \\ |
| 331 |
> |
$2\mu1e$ & 0\% & 0\% & 0\% & 0\% & 0\% \\ |
| 332 |
> |
$3\mu$ & 0\% & 0\% & 0\% & 0\% & 0\% \\ |
| 333 |
> |
\hline \hline |
| 334 |
> |
|
| 335 |
> |
& \multicolumn{5}{c}{$\Z \to \mu\mu$ and \W decay modes below} \\ |
| 336 |
> |
Reconstruction channel & $e\nu$ |
| 337 |
> |
& $\mu\nu$ |
| 338 |
> |
& $\tau\nu \to e\nu\nu$ |
| 339 |
> |
& $\tau\nu \to \mu\nu\nu$ |
| 340 |
> |
& $\tau\nu \to {\rm hadrons~}\nu$ |
| 341 |
> |
\\ \hline |
| 342 |
> |
$3e$ & 0\% & 0\% & 0\% & 0\% & 0\% \\ |
| 343 |
> |
$2e1\mu$ & 0.0104\% & 0\% & 0\% & 0\% & 0\% \\ |
| 344 |
> |
$2\mu1e$ & 19.6\% & 0.0208\% & 5.56\% & 0\% & 0.18\% \\ |
| 345 |
> |
$3\mu$ & 0\% & 23.4\% & 0.0573\% & 6.77\% & 0.0164\% \\ |
| 346 |
> |
\hline \hline |
| 347 |
> |
\end{tabular} |
| 348 |
> |
\end{center} |
| 349 |
> |
\caption{Selection efficiency for signal events in the four selection channels for the different |
| 350 |
> |
generated \W and \Z decay channels.} |
| 351 |
> |
\label{tab:wz-effimatrix} |
| 352 |
> |
|
| 353 |
> |
%\end{table} |
| 354 |
> |
%\begin{table}[tbp] |
| 355 |
> |
\begin{center} |
| 356 |
> |
\begin{tabular}{llcc} \hline |
| 357 |
> |
& & \multicolumn{2}{c}{Generated decay} \\ |
| 358 |
> |
& & \multicolumn{2}{c}{$\Z \to ee $} \\ |
| 359 |
> |
Selection channel & & $\W \to e\nu$ & $\W \to \mu\nu$ \\ |
| 360 |
> |
\hline \hline |
| 361 |
> |
\multicolumn{4}{c}{all} \\ \hline |
| 362 |
> |
$3e$ & all & 1644 events & 3 events \\ |
| 363 |
> |
$3e$ & matched \Z & 93$\pm$1\% & 100\%\\ |
| 364 |
> |
$3e$ & matched \W & 92$\pm$1\% & 0\\ |
| 365 |
> |
$3e$ & matched \WZ & 91$\pm$1\% & 0\\ |
| 366 |
> |
\hline \hline |
| 367 |
> |
|
| 368 |
> |
\multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline |
| 369 |
> |
$3e$ & all & 1602 events & 0 events \\ |
| 370 |
> |
$3e$ & matched \Z & 94$\pm$1\% & 0\\ |
| 371 |
> |
$3e$ & matched \W & 92$\pm$1\% & 0\\ |
| 372 |
> |
$3e$ & matched \WZ & 91$\pm$1\% & 0\\ |
| 373 |
> |
\hline \hline |
| 374 |
> |
|
| 375 |
> |
\multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline |
| 376 |
> |
$3e$ & all & 42 events & 3 events \\ |
| 377 |
> |
$3e$ & matched \Z & 93$\pm$4\% & 100\%\\ |
| 378 |
> |
$3e$ & matched \W & 91 $\pm$5\% & 0\\ |
| 379 |
> |
$3e$ & matched \WZ & 91$\pm$5\% & 0\\ |
| 380 |
> |
\hline \hline |
| 381 |
> |
|
| 382 |
> |
\multicolumn{4}{c}{all} \\ \hline |
| 383 |
> |
$2e1\mu$ & all & 0 events & 1746 events \\ |
| 384 |
> |
$2e1\mu$ & matched \Z & 0 & 100\%\\ |
| 385 |
> |
$2e1\mu$ & matched \W & 0 & 100\%\\ |
| 386 |
> |
$2e1\mu$ & matched \WZ & 0 & 100\%\\ |
| 387 |
> |
\hline \hline |
| 388 |
> |
|
| 389 |
> |
\multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline |
| 390 |
> |
$2e1\mu$ & all & 0 events & 1715 events \\ |
| 391 |
> |
$2e1\mu$ & matched \Z & 0 & 100\%\\ |
| 392 |
> |
$2e1\mu$ & matched \W & 0 & 100\%\\ |
| 393 |
> |
$2e1\mu$ & matched \WZ & 0 & 100\%\\ |
| 394 |
> |
\hline \hline |
| 395 |
> |
|
| 396 |
> |
\multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline |
| 397 |
> |
$2e1\mu$ & all & 0 & 31 \\ |
| 398 |
> |
$2e1\mu$ & matched \Z & 0 & 100\%\\ |
| 399 |
> |
$2e1\mu$ & matched \W & 0 & 100\%\\ |
| 400 |
> |
$2e1\mu$ & matched \WZ & 0 & 100\% \\ \hline \hline |
| 401 |
> |
\end{tabular} |
| 402 |
> |
\end{center} |
| 403 |
> |
\caption{Fractions of events with correctly matched leptons |
| 404 |
> |
to true decay product of \W and \Z decays for final states |
| 405 |
> |
with generated $\Z\to ee$ decays} |
| 406 |
> |
\label{tab:wz-matcheffi-Zee} |
| 407 |
> |
\end{table} |
| 408 |
> |
|
| 409 |
> |
|
| 410 |
> |
|
| 411 |
> |
\begin{table}[tbp] |
| 412 |
> |
\begin{center} |
| 413 |
> |
\begin{tabular}{llcc} \hline |
| 414 |
> |
& & \multicolumn{2}{c}{Generated decay:} \\ |
| 415 |
> |
& & \multicolumn{2}{c}{$\Z \to \mu\mu $} \\ |
| 416 |
> |
Selection channel & & $\W \to e\nu$ & $\W \to \mu\nu$ |
| 417 |
> |
\\ |
| 418 |
> |
\hline \hline |
| 419 |
> |
\multicolumn{4}{c}{all} \\ \hline |
| 420 |
> |
$2\mu1e$ & all & 1895 events & 2 events \\ |
| 421 |
> |
$2\mu1e$ & matched \Z & 100\% & 100\%\\ |
| 422 |
> |
$2\mu1e$ & matched \W & 99$\pm$1\% & 0\\ |
| 423 |
> |
$2\mu1e$ & matched \WZ & 99$\pm$1\% & 0\\ |
| 424 |
> |
\hline \hline |
| 425 |
> |
|
| 426 |
> |
\multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline |
| 427 |
> |
$2\mu1e$ & all & 1847 events & 0 events \\ |
| 428 |
> |
$2\mu1e$ & matched \Z & 100\% & 0\\ |
| 429 |
> |
$2\mu1e$ & matched \W & 99$\pm$1\% & 0\\ |
| 430 |
> |
$2\mu1e$ & matched \WZ & 99$\pm$1\% & 0\\ |
| 431 |
> |
\hline \hline |
| 432 |
> |
|
| 433 |
> |
\multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline |
| 434 |
> |
$2\mu1e$ & all & 48 events & 2 events \\ |
| 435 |
> |
$2\mu1e$ & matched \Z & 100\% & 100\%\\ |
| 436 |
> |
$2\mu1e$ & matched \W & 94$\pm$3.5\%& 0\\ |
| 437 |
> |
$2\mu1e$ & matched \WZ & 94$\pm$3.5\% & 0\\ |
| 438 |
> |
\hline \hline |
| 439 |
> |
|
| 440 |
> |
\multicolumn{4}{c}{all} \\ \hline |
| 441 |
> |
$3\mu$ & all & 0 events & 2251 events \\ |
| 442 |
> |
$3\mu$ & matched \Z & 0 & 94$\pm$1\%\\ |
| 443 |
> |
$3\mu$ & matched \W & 0 & 93$\pm$1\%\\ |
| 444 |
> |
$3\mu$ & matched \WZ & 0 & 93$\pm$1\%\\ |
| 445 |
> |
\hline \hline |
| 446 |
> |
|
| 447 |
> |
\multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline |
| 448 |
> |
$3\mu$ & all & 0 events & 2207 events \\ |
| 449 |
> |
$3\mu$ & matched \Z & 0 & 94$\pm$1\%\\ |
| 450 |
> |
$3\mu$ & matched \W & 0 & 93$\pm$1\%\\ |
| 451 |
> |
$3\mu$ & matched \WZ & 0 & 93$\pm$1\%\\ |
| 452 |
> |
\hline \hline |
| 453 |
> |
|
| 454 |
> |
\multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline |
| 455 |
> |
$3\mu$ & all & 0 events & 44 events \\ |
| 456 |
> |
$3\mu$ & matched \Z & 0 & 91$\pm$4\%\\ |
| 457 |
> |
$3\mu$ & matched \W & 0 & 91$\pm$4\%\\ |
| 458 |
> |
$3\mu$ & matched \WZ & 0 & 91$\pm$4\%\\ \hline \hline |
| 459 |
> |
\end{tabular} |
| 460 |
> |
\end{center} |
| 461 |
> |
\caption{Fractions of MC \WZ events with correctly matched leptons |
| 462 |
> |
to true decay product of \W and \Z decays for final states |
| 463 |
> |
with generated $\Z\to \mu\mu$ decays} |
| 464 |
> |
\label{tab:wz-matcheffi-Zmumu} |
| 465 |
> |
\end{table} |
| 466 |
|
|
| 467 |
|
|
| 468 |
< |
\subsection{Signal extraction} |
| 468 |
> |
%\subsection{Signal extraction} |
| 469 |
> |
%\input D0Matrix |
| 470 |
> |
\input zjetbackground |
| 471 |
> |
|
| 472 |
> |
|
| 473 |
> |
\subsection{Complementary studies: can we use the neutrino?} |
| 474 |
> |
|
| 475 |
> |
In $\WZ \to \ell^{\pm}\nu \ellell (\ell=e,\mu)$ events, the neutrino |
| 476 |
> |
coming from the \W-boson decay leaves the detector with a significant |
| 477 |
> |
amount of energy, which should reflect in a large transverse missing |
| 478 |
> |
energy measurement. On the other side, no large MET is expected for |
| 479 |
> |
the most important background categories, especially \Zjets, |
| 480 |
> |
\Zbbbar, \ZZ and \Zgamma. This expectation is confirmed, as can be |
| 481 |
> |
seen in Figure~\ref{fig:met}. |
| 482 |
> |
|
| 483 |
> |
Another variable sensitive to the presence of the neutrino |
| 484 |
> |
is the W transverse mass $m_T^W$, obtained by combining the missing |
| 485 |
> |
energy vector and the lepton associated to the \W-boson decay. |
| 486 |
> |
The distribution of $m_T^W$ is shown in Figure~\ref{fig:mtw}. |
| 487 |
> |
The signal yield could be extracted from that distribution. |
| 488 |
> |
This requires however additional studies and it has not been |
| 489 |
> |
done at this stage. |
| 490 |
> |
|
| 491 |
> |
|
| 492 |
> |
\section{Systematic uncertainties} |
| 493 |
> |
\input Sys |
| 494 |
> |
|
| 495 |
> |
|
| 496 |
> |
\begin{figure}[bt] |
| 497 |
> |
\begin{center} |
| 498 |
> |
\scalebox{0.8}{\includegraphics{figs/met_by_channel.eps}} |
| 499 |
> |
\caption{Missing transverse energy for the four signal categories. |
| 500 |
> |
The distributions show the number of expected events |
| 501 |
> |
for $1 fb^{-1}$. Only events with 81 GeV $< M_Z < $ 101 \gev |
| 502 |
> |
are shown. All selection cuts are applied.} |
| 503 |
> |
\label{fig:met} |
| 504 |
> |
\end{center} |
| 505 |
> |
\end{figure} |
| 506 |
> |
|
| 507 |
> |
\begin{figure}[bt] |
| 508 |
> |
\begin{center} |
| 509 |
> |
\scalebox{0.8}{\includegraphics{figs/mtw_by_channel.eps}} |
| 510 |
> |
\caption{\W transverse mass for the four signal categories. |
| 511 |
> |
The distributions show the number of expected events |
| 512 |
> |
for $1 fb^{-1}$. Only events with 81 GeV $< M_Z < $ 101 GeV are shown. |
| 513 |
> |
All selection cuts are applied.} |
| 514 |
> |
\label{fig:mtw} |
| 515 |
> |
\end{center} |
| 516 |
> |
\end{figure} |
| 517 |
|
|
| 518 |
|
|
| 124 |
– |
\subsection{Systematic uncertainties} |
| 519 |
|
|
| 520 |
|
|
| 521 |
|
|
