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\section{Non $t\bar{t}$ Backgrounds}
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\label{sec:othBG}
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Backgrounds from divector bosons and single top
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can be reliably estimated from Monte Carlo.
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They are negligible compared to $t\bar{t}$.
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Backgrounds from Drell Yan are also expected
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to be negligible from MC. However one always
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worries about the modeling of tails of the \met.
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In the context of other dilepton analyses we
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have developed a data driven method to estimate
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the number of Drell Yan events\cite{ref:dy}.
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The method is based on counting the number of
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$Z$ candidates passing the full selection, and
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then scaling by the expected ratio of Drell Yan
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events outside vs. inside the $Z$ mass
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window.\footnote{A correction based on $e\mu$ events
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is also applied.} This ratio is typically 0.1.
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When find no dilepton events with invariant mass
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consistent with the $Z$ in the signal region.
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Using the value of 0.1 for the ratio described above, this
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means that the Drell Yan background in our signal
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region is $< 0.23\%$ events at the 90\% confidence level.
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{\color{red} (If we find 1 event this will need to be adjusted)}.
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Finally, we can use the ``Fake Rate'' method\cite{ref:FR}
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to predict
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the number of events with one fake lepton. We select
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events where one of the leptons passes the full selection and
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the other one fails the full selection but passes the
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``Fakeable Object'' selection of
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Reference~\cite{ref:FR}.\footnote{For electrons we use
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the V3 fakeable object definition to avoid complications
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associated with electron ID cuts applied in the trigger.}
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We then weight each event passing the full selection
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by FR/(1-FR) where FR is the ``fake rate'' for the
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fakeable object. {\color{red} The results are...} |
