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\section{Introduction}
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\label{sec:introduction}
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The study of multiple gauge-boson production at the TeV scale
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constitutes a unique opportunity to test the standard model of
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electroweak interactions at the highest possible energies.
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The production of \WZ\ events in \pp\ collisions at the LHC allows to
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probe triple gauge-boson couplings and, therefore, non-Abelian gauge
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symmetry of the standard model at energies never attained
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before. Any deviation of the strength of these couplings from
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their standard model expectations manifests the new physics.
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In addition, multi-lepton final states of \WZ\ production constitutes
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an important background to potential new phenomena,
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in particular Supersymmetry. A good understanding of the \WZ\
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production-process is of paramount importance in the first phase
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of the LHC data-taking before any discovery can be claimed.
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At the same time, deviation of the \WZ\ production rate and
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differential cross sections from the standard model predictions
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could hint to the direct production of new heavy particles.
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In this note, we present results on the study of \WZ\ production
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based on the full simulation of the CMS detector. \WZ production in \pp\
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collisions at the LHC mainly proceeds through quark annihilation into
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an intermediate W boson, see Fig.~\ref{fig:graph}. Cross section of
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about 31 pb and 19 pb are expected for the $W^+\Z$ and $W^-\Z$ final states,
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respectively~\cite{Haywood:1999qg}. There are four configuration of
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final state leptons considered in this analysis: $e^\pm \epem$,
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$\mu^\pm \epem$, $\rm e^\pm \mu^+\mu^-$, and $\mu^\pm \mu^+\mu^-$.
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Main instrumental background to all of the four signatures is due to
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misidentified jets from top quark production and associative \Z or \W boson
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and jets production. Next in significance is a background from
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converted photons from $Z^0\gamma$ and $\W\gamma$ processes
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that are identified as electrons. The only physics background to \WZ\ final state is $\Z\Z$
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production with one of the leptons being mis-reconstructed or lost.
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The structure of this note is as follows. We describe the signal
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and background modeling in Section~\ref{sec:gen}. The information
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on triggering and reconstruction of events is given in
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Section~\ref{sec:eventReconstruction}. We present the methods of measuring
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signal and background yields and estimate systematic uncertainties in
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Sections~\ref{sec:SignalExt} and~\ref{sec:systematic}, respectively.
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The summary of the analysis and results drawn with an emphasis on the
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\WZ\ observation in early LHC data are given in Section~\ref{sec:results}.
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\begin{figure}[hbt]
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\begin{center}
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\scalebox{0.5}{\includegraphics{figs/DiBosonProd.eps}}
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\caption{Dominant spectator Feynman diagrams for \WZ
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production in $\proton\proton$ collisions. The
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\mbox{$\pp\to\W\Z$} reaction occurs mainly through the $s$-channel
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$\q\qbar^{\prime}$ amplitude (left diagram), involving the $WWZ$ triple
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gauge-boson coupling.}
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\label{fig:graph}
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\end{center}
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\end{figure}
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