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claudioc |
1.1 |
\section{Limit on new physics}
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\label{sec:limit}
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claudioc |
1.2 |
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{\bf \color{red} The numbers in this Section need to be double checked.}
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As discussed in Section~\ref{sec:results}, we see one event
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in the signal region, defined as SumJetPt$>$300 GeV and
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\met/$\sqrt{\rm SumJetPt}>8.5$ GeV$^{\frac{1}{2}}$.
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The background prediction from the SM Monte Carlo is
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1.4 $\pm$ 0.5 events, where the uncertainty comes from
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the jet energy scale (30\%, see Section~\ref{sec:systematics}),
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the luminosity (10\%), and the lepton/trigger
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efficiency (10\%)\footnote{Other uncertainties associated with
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claudioc |
1.8 |
the modeling of $t\bar{t}$ in MadGraph have not been evaluated.
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The uncertainty on $pp \to \sigma(t\bar{t}$ is also not included.}.
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claudioc |
1.2 |
The data driven background predictions from the ABCD method
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and the $P_T(\ell\ell)$ method are 1.5 $\pm$ 0.9 and
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benhoob |
1.6 |
$2.5 \pm 2.2$ events, respectively.
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claudioc |
1.2 |
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These three predictions are in good agreement with each other
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and with the observation of one event in the signal region.
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benhoob |
1.5 |
We calculate a Bayesian 95\% CL upper limit\cite{ref:bayes.f}
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claudioc |
1.2 |
on the number of non SM events in the signal region to be 4.1.
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benhoob |
1.7 |
This was calculated using a background prediction of $N_{BG}=1.4 \pm 1.1$
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claudioc |
1.2 |
events. The upper limit is not very sensitive to the choice of
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$N_{BG}$ and its uncertainty.
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To get a feeling for the sensitivity of this search to some
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popular SUSY models, we remind the reader of the number of expected
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benhoob |
1.4 |
LM0 and LM1 events from Table~\ref{tab:sigcont}: $6.5 \pm 1.3$
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events and $2.6 \pm 0.4$ respectively, where the uncertainties
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claudioc |
1.2 |
are from energy scale (Section~\ref{sec:systematics}), luminosity,
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and lepton efficiency.
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claudioc |
1.8 |
In Figure~\ref{fig:response} we provide the response functions for the
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SumJetPt and \met/$\sqrt{\rm SumJetPt}$ in MC, as well as the
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efficiency for the cuts on these quantities used in defining the
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signal region (SumJetPt $>$ 300 GeV and \met/$\sqrt{\rm SumJetPt} > 8.5$
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Gev$^{\frac{1}{2}}$). We see that the average SumJetPt response
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in the Monte Carlo
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is very close to one, with an RMS of order 10\%. The
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response of \met/$\sqrt{\rm SumJetPt}$ is approximately 0.94 with an
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RMS of 15\%.
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Using this information as well as the kinematical
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claudioc |
1.2 |
cuts described in Section~\ref{sec:eventSel} and the lepton efficiencies
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of Figures~\ref{fig:effttbar}, one should be able to confront
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any existing or future model via a relatively simple generator
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level study by comparing the expected number of events in 35 pb$^{-1}$
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claudioc |
1.8 |
with our upper limit of 4.1 events.
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\begin{figure}[tbh]
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\begin{center}
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\includegraphics[width=\linewidth]{selectionEff.png}
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\caption{\label{fig:response} Left plots: the efficiencies
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as a function of the true quantities for the SumJetPt (top) and
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tcMET/$\sqrt{\rm SumJetPt}$ (bottom) requirements for the signal
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region as a function of their true values. The value of the
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cuts is indicated by the vertical line.
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Right plots: The average response and its RMS for the SumJetPt
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(top) and tcMET/$\sqrt{\rm SumJetPt}$ (bottom) measurements.
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The response is defined as the ratio of the reconstructed quantity
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to the true quantity in MC. These plots are done using the LM0
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Monte Carlo, but they are not expected to depend strongly on
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the underlying physics.}
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\end{center}
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\end{figure}
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