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\fixme{need to summarize decay mode}
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The Tau Neural classifier algorithm significantly improves tau identification
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performance compared to isolation--based strategies~\cite{PFT08001} used in
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previous CMS strategies. Figure~\ref{fig:finalPerfCurve} compares the
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performance of the ``shrinking cone'' isolation tau--identification
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algorithm~\cite{PFT08001} to the performance of the TaNC for a scan of
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requirements on the transformed neural network output. For tau--candidates with
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transverse momentum between 20 and 50 GeV/c, the TaNC operating cut can be
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chosen such that the two methods have identical signal efficiency; at this point the TaNC
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algorithm reduces the background fake rate by an additional factor of
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\fixme{get exact}.
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The discriminator output of the TaNC algorithm is a continuous quantity,
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enabling analysis specific optimization of the selection to maximize
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sensitivity. For the convenience of the user, four operating point benchmark
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selections are provided in addition to the continuous output. The four operating
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points are chosen such that for tau--candidates with transverse momentum between
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20 and 50 GeV/c, the expected QCD di--jet fake rate will be 0.1\%, 0.25\%,
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0.50\% and 1.0\%, respectively. The signal efficiency and QCD di--jet fake rate
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versus tau--candidate transverse momentum and pseudo--rapidity for the four
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benchmark points and the isolation based tau identification are show in
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figure~\ref{fig:kinematicPerformance}.
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\fixme{needs a zippy end}
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\begin{figure}[t]
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\setlength{\unitlength}{1mm}
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\begin{center}
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\begin{picture}(150, 150)(0,0)
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\put(0.5, 0.5)
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{\mbox{\includegraphics*[height=150mm]{figures/20_pt_50_perf_curve_from_5_pt_200_transform_plain_test_wrt_classic.pdf}}}
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\end{picture}
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\caption{
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Performance curve (red) of the TaNC tau identification for various
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requirements on the output transformed according to
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equation~\ref{eq:tancTransform}. The horizontal axis is the efficiency for
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true taus with transverse momentum between 20 and 50 GeV/c to satisfy the tau
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identification requirements. The vertical axis gives the rate at which QCD
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di--jets with generator--level transverse momentum between 20 and 50 GeV/c are incorrectly
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identified as taus. The performance point for the same tau--candidates using
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the isolation based tau--identification~\cite{PFT08001} used in many previous
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CMS analyses is indicated by the black star in the figure.
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}
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\label{fig:finalPerfCurve}
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\end{center}
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\end{figure}
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\begin{figure}[t]
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\setlength{\unitlength}{1mm}
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\begin{center}
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\begin{picture}(150, 150)(0,0)
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\put(2.5, 75)
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{\mbox{\includegraphics*[height=70mm]{figures/eff_background_pt.pdf}}}
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\put(75, 75)
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{\mbox{\includegraphics*[height=70mm]{figures/eff_background_eta.pdf}}}
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\put(2.5, 0)
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{\mbox{\includegraphics*[height=70mm]{figures/eff_signal_pt.pdf}}}
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\put(75, 0)
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{\mbox{\includegraphics*[height=70mm]{figures/eff_signal_pt.pdf}}}
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\end{picture}
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\caption{
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\fixme{add caption and legend, isolation+1 or 3 prong is the black trend,
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pt greater than 20 cut applied on eta plots}
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}
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\label{fig:kinematicPerformance}
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\end{center}
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\end{figure}
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|
