claudioc/OSNote2010/otherBG.tex

\section{Non $t\bar{t}$ Backgrounds}
\label{sec:othBG}

Backgrounds from divector bosons and single top
can be reliably estimated from Monte Carlo.
They are negligible compared to $t\bar{t}$. 
 
Backgrounds from Drell Yan are also expected
to be negligible from MC.  However one always 
worries about the modeling of tails of the \met. 
In the context of other dilepton analyses we 
have developed a data driven method to estimate 
the number of Drell Yan events\cite{ref:dy}.
The method is based on counting the number of
$Z$ candidates passing the full selection, and 
then scaling by the expected ratio of Drell Yan
events outside vs. inside the $Z$ mass 
window.\footnote{A correction based on $e\mu$ events 
is also applied.}  This ratio is typically 0.1.  

When  find no dilepton events with invariant mass
consistent with the $Z$ in the signal region.
Using the value of 0.1 for the ratio described above, this 
means that the Drell Yan background in our signal 
region is $< 0.23\%$ events at the 90\% confidence level.
{\color{red} (If we find 1 event this will need to be adjusted)}.

Finally, we can use the ``Fake Rate'' method\cite{ref:FR} 
to predict 
the number of events with one fake lepton. We select
events where one of the leptons passes the full selection and 
the other one fails the full selection but passes the 
``Fakeable Object'' selection of 
Reference~\cite{ref:FR}.\footnote{For electrons we use
the V3 fakeable object definition to avoid complications 
associated with electron ID cuts applied in the trigger.} 
We then weight each event passing the full selection
by FR/(1-FR) where FR is the ``fake rate'' for the 
fakeable object.  {\color{red} The results are...}
Revision:	1.1
Committed:	Fri Oct 29 02:29:40 2010 UTC (14 years, 6 months ago) by claudioc
Content type:	application/x-tex
Branch:	MAIN
Log Message:	blah
#	User	Rev	Content
1	claudioc	1.1	\section{Non $t\bar{t}$ Backgrounds}
2			\label{sec:othBG}
3
4			Backgrounds from divector bosons and single top
5			can be reliably estimated from Monte Carlo.
6			They are negligible compared to $t\bar{t}$.
7
8			Backgrounds from Drell Yan are also expected
9			to be negligible from MC. However one always
10			worries about the modeling of tails of the \met.
11			In the context of other dilepton analyses we
12			have developed a data driven method to estimate
13			the number of Drell Yan events\cite{ref:dy}.
14			The method is based on counting the number of
15			$Z$ candidates passing the full selection, and
16			then scaling by the expected ratio of Drell Yan
17			events outside vs. inside the $Z$ mass
18			window.\footnote{A correction based on $e\mu$ events
19			is also applied.} This ratio is typically 0.1.
20
21			When find no dilepton events with invariant mass
22			consistent with the $Z$ in the signal region.
23			Using the value of 0.1 for the ratio described above, this
24			means that the Drell Yan background in our signal
25			region is $< 0.23\%$ events at the 90\% confidence level.
26			{\color{red} (If we find 1 event this will need to be adjusted)}.
27
28			Finally, we can use the ``Fake Rate'' method\cite{ref:FR}
29			to predict
30			the number of events with one fake lepton. We select
31			events where one of the leptons passes the full selection and
32			the other one fails the full selection but passes the
33			``Fakeable Object'' selection of
34			Reference~\cite{ref:FR}.\footnote{For electrons we use
35			the V3 fakeable object definition to avoid complications
36			associated with electron ID cuts applied in the trigger.}
37			We then weight each event passing the full selection
38			by FR/(1-FR) where FR is the ``fake rate'' for the
39			fakeable object. {\color{red} The results are...}