--- ttbar/p20_taujets_note/Preselection.tex	2011/05/18 21:30:39	1.1
+++ ttbar/p20_taujets_note/Preselection.tex	2011/06/01 01:20:54	1.2
@@ -3,7 +3,7 @@ Up to this point we have presented the d
 the Monte Carlo samples and corrections applied to them (Sections \ref{sub:mcsample} and \ref{sub:mcsample_xseccorr}),
 the trigger used and its simulation (Section \ref{sec:trig_param}) and the object ID
 method (Section \ref{sec:objects}). Now we describe the next steps of the analysis
-towards the final crosse section measurement:
+towards the final cross section measurement:
 
 \begin{itemize}
 \item Preselection (section \ref{sub:Preselection}): at least 4 jets, at least one $\tau$ with NN$>$0.3 and $p_{T}>10$ GeV/$c$,
@@ -17,16 +17,17 @@ different $\not\!\! E_{T}$ significance
 \item Topological Variables (section \ref{sub:Topo}): section showing final analysis plots of topological
 variables of interest.
 \item Cross Section (section \ref{sub:xsect}) The signal fraction determination is 
-combined with integrated luminosity measurement to calculate the cross section.  
-Systematic uncertainties are determined by fluctuating the significant components 
-up and down by one standard deviation one at a time, propagating it through the entire procedure. 
+combined with the integrated luminosity measurement to calculate the cross section.  
+The systematic errors are estimated by changing
+the values up-down by 1 sigma independently for each component
+at a time and then propagating them through the entire procedure. 
 \end{itemize}
 
 \section{\label{sub:Preselection}Preselection}
 
 The preselection is the first step of the analysis. The cuts presented here were chosen in order to provide the best
 background reduction and enhance the $t\bar{t}$  content at this point. The cuts are the similar to those used in the 
-p17 analysis \cite{p17_note} except that for this time we opted to optimize the value of $\not\!\! E_{T}$ 
+p17 analysis \cite{p17_note} except that this time we optimized the value of $\not\!\! E_{T}$ 
 significance along with the sets of variables we used as inputs to NN training (Section \ref{sub:NN}). 
 Cuts shown below were applied to samples shown in Table \ref{used_mc} as well as to data as shown in Section \ref{sub:datasample}.
 
@@ -38,10 +39,16 @@ Cuts shown below were applied to samples
 %\end{itemize}
 
 \begin{itemize}
-\item At least 4 jets with $p_{T}>15$ GeV and $\eta <$2.5, with leading (in $p_{T}$) jet $p_{T}>35$ GeV and second and third jets have $p_{T}>25$ GeV
+\item Duplicate event removal and event quality
+\item At least 4 jets with $p_{T}>15$ GeV and $|\eta| <$2.5, with leading (in $p_{T}$) jet $p_{T}>35$ GeV and second and third jets have $p_{T}>25$ GeV
 \item at least one $\tau$ with NN$>$0.3 and $p_{T}>10$ GeV 
 \item 15 GeV $\leq$ $\not\!\! E_{T}$ $\leq$ 500 GeV
-\item $\not\!\! E_{T}$ significance $\geq$ 4.0 
+\item $\not\!\! E_{T}$ significance $\geq$ 4.0.Missing transverse energy significance is a 
+measure of the likelihood of $\not\!\! E_{T}$
+arising from physical sources. It is computed from calculated resolutions of physical objects (jets, electrons,
+muons and unclustered energy) \cite{p17_note,METsig}.
+\item Vertex selection: at least 3 tracks and $|z_{max}|$ = 60 cm.
+
 \item No isolated electron or muon. This is done in order to ensure orthogonality with other \dzero \hspace{1pt} 
 measurements (\cite{l+jets} and \cite{dilepton}) - events that pass the lepton preselection cuts from these measurements 
 were vetoed. Also events that pass the all-jets analysis preselection cuts (described in the alljet analysis note \cite{alljet}) 
@@ -59,9 +66,7 @@ are rejected here.
 
 Among all preselection cuts one of them requires a more detailed description at this point since it represents
 an improvement upon the old p17 analysis: $\not\!\! E_{T}$ significance.
-Missing transverse energy significance is a measure of the likelihood of $\not\!\! E_{T}$
-arising from physical sources. It is computed from calculated resolutions of physical objects (jets, electrons,
-muons and unclustered energy) \cite{p17_note,METsig}. Initially no $\not\!\! E_{T}$ significance
+. Initially no $\not\!\! E_{T}$ significance
 was applied neither on MC nor on data. In this analysis we decided
 to optimize the $\not\!\! E_{T}$ significance cut along with the NN optimization itself. 
 After finishing the $\not\!\! E_{T}$ significance optimization 
@@ -74,36 +79,34 @@ In data, initially the sample contained
 
 
 Another relevant aspect of the preselection is the usage of Particle Selector (only applied to MC samples). 
-In this step we aimed to select a particular $\ttbar$ final state, namely, we split $W$ decay 
+In this step we select a specific $\ttbar$ final state, namely, we split $W$ decay 
 into $W \rightarrow e/\mu /\tau $ and 
-tracked separate efficiencies for each of these processes. In this step we selected hadronic decays of tau,
-and at the same events where tau decays into electrons and muons were put into $e + jets$ and $\mu + jets$ samples.
-As in p17, we decided to do not split the dilepton sample in different lepton flavors.
+tracked separate efficiencies for each of these processes. In this step we selected hadronic decays of tau.
+Events where the tau decays into an electron or a muon were put into $e + jets$ and $\mu + jets$ samples.
+As in p17, we decided to not split the dilepton sample in different lepton flavors.
 
-Before proceeding to the next step, it is important to describe the result of the preselection
-in terms of its efficiencies since all the rest of analysis strongly depends on the cuts applied at this level. 
 As previously described, $t\bar{t}$ were generated by ALPGEN. In ALPGEN, different process with different
-numbers of partons have different cross-sections and number of events. This fact must be taken into account when calculating the 
-efficiencies, namely, efficiencies must be properly scaled to the luminosity (4951.85 pb$^{-1}$) of the sample. Tables 
-\ref{ttbar_alp} and III show the number beforementioned for $t\bar{t} \rightarrow$ lepton + jets
+numbers of partons have different cross sections and number of events. This fact must be taken into account when calculating the 
+efficiencies, namely, efficiencies must be properly scaled to the luminosity of the sample (4951.85 pb$^{-1}$). Tables 
+7 and 8 show the ALPGEN weights for $t\bar{t} \rightarrow$ lepton + jets
 %VI and VII show the number beforementioned for $t\bar{t} \rightarrow$ lepton + jets
 and $t\bar{t} \rightarrow$ dilepton respectively.
 
 \begin{table}[h]
 \begin{center}
 \begin{tabular}{|c|r|r|r|} \hline
-Process   & \# of events & cross-section (pb) & alpgen weight    \\ \hline
+Process   & \# of events & cross section (pb) & alpgen weight    \\ \hline
 
 \hline
 
 
-0 light parton     &  \multicolumn{1}{c|}{777068}   &  \multicolumn{1}{c|}{1.4} &  \multicolumn{1}{c|}{0.00892}  \\ \hline
+$t\bar{t}$ + 0 light parton     &  \multicolumn{1}{c|}{777068}   &  \multicolumn{1}{c|}{1.400} &  \multicolumn{1}{c|}{0.00892}  \\ \hline
 
 
-1 light parton      &  \multicolumn{1}{c|}{457782} &  \multicolumn{1}{c|}{0.577} &  \multicolumn{1}{c|}{0.00624} \\ \hline
+$t\bar{t}$ + 1 light parton      &  \multicolumn{1}{c|}{457782} &  \multicolumn{1}{c|}{0.577} &  \multicolumn{1}{c|}{0.00624} \\ \hline
 
 
-$\geq$ 2 light partons     &  \multicolumn{1}{c|}{321166}   &  \multicolumn{1}{c|}{0.267} &  \multicolumn{1}{c|}{0.00412} \\ \hline
+$t\bar{t}$ + $\geq$ 2 light partons     &  \multicolumn{1}{c|}{321166}   &  \multicolumn{1}{c|}{0.267} &  \multicolumn{1}{c|}{0.00412} \\ \hline
 \end{tabular}
 \caption{$t\bar{t} \rightarrow$ lepton + jets ALPGEN weights.}
 \end{center}
@@ -114,7 +117,7 @@ $\geq$ 2 light partons     &  \multicolu
 \begin{table}[h]
 \begin{center}
 \begin{tabular}{|c|r|r|r|} \hline
-Process   & \# of events & cross-section (pb) & alpgen weight    \\ \hline
+Process   & \# of events & cross section (pb) & alpgen weight    \\ \hline
 
 \hline
 
@@ -152,7 +155,7 @@ Electron veto & 1282 &  $ 98.93 \pm 0.01
 Muon veto & 1282 &  $ 99.93 \pm 0.01 ~\% $ &  $ 11.48 \pm 0.03~\% $ \\ 
 MET selection & 1218 &  $ 95.05 \pm 0.05 ~\% $ &  $ 10.91 \pm 0.02~\% $  \\ 
 MET significance & 772 &  $ 63.39 \pm 0.12 ~\% $ &  $ 6.92 \pm 0.02~\% $  \\
-NN tau cut & 394 &  $ 53.51 \pm 0.15 ~\% $ &  $ 3.70 \pm 0.02~\% $  \\ \hline
+tau selection & 394 &  $ 53.51 \pm 0.15 ~\% $ &  $ 3.70 \pm 0.02~\% $  \\ \hline
 
 \end{tabular}
 \caption{Preselection $t\overline{t}\rightarrow\tau+jets$ cut flow} 
@@ -176,7 +179,7 @@ Electron veto & 1048 &  $ 54.94 \pm 0.10
 Muon veto & 1047 &  $ 99.95 \pm 0.01 ~\% $ &  $ 9.38 \pm 0.02~\% $ \\ 
 MET selection & 1002 &  $ 95.64 \pm 0.05~\% $ &  $ 8.97 \pm 0.02~\% $  \\ 
 MET significance & 669 &  $ 66.74 \pm 0.13 ~\% $ &  $ 5.99 \pm 0.02~\% $  \\
-NN tau cut & 395 &  $ 59.12 \pm 0.16 ~\% $ &  $ 3.54 \pm 0.02~\% $  \\ \hline
+tau selection & 395 &  $ 59.12 \pm 0.16 ~\% $ &  $ 3.54 \pm 0.02~\% $  \\ \hline
 
 \end{tabular}
 \caption{Preselection $t\overline{t}\rightarrow e+jets$ cut flow}
@@ -200,7 +203,7 @@ Electron veto & 1967 &  $ 99.59 \pm 0.01
 Muon veto &  1170 &  $ 59.48 \pm 0.09 ~\% $ &  $ 10.48 \pm 0.02~\% $ \\ 
 MET selection & 1127 &  $ 96.31 \pm 0.04~\% $ &  $ 10.09 \pm 0.02~\% $  \\ 
 MET significance & 812 &  $ 72.06 \pm 0.11 ~\% $ &  $ 7.27 \pm 0.02~\% $  \\
-NN tau cut & 186 &  $ 22.95 \pm 0.13 ~\% $ &  $ 1.67 \pm 0.01~\% $  \\ \hline
+tau selection & 186 &  $ 22.95 \pm 0.13 ~\% $ &  $ 1.67 \pm 0.01~\% $  \\ \hline
 
 \end{tabular}
 \caption{Preselection $t\overline{t}\rightarrow \mu +jets$ cut flow}
@@ -223,7 +226,7 @@ Electron veto & 110 &  $ 76.14 \pm 0.13
 Muon veto & 83 &  $ 75.08 \pm 0.16 ~\% $ &  $ 2.95 \pm 0.01~\% $ \\ 
 MET selection & 80 &  $ 96.45 \pm 0.08~\% $ &  $ 2.84 \pm 0.01~\% $  \\ 
 MET significance & 60 &  $ 75.32 \pm 0.19 ~\% $ &  $ 2.14 \pm 0.01~\% $  \\
-NN tau cut & 38 &  $ 63.21 \pm 0.24 ~\% $ &  $ 1.35 \pm 0.01~\% $  \\ \hline
+tau selection & 38 &  $ 63.21 \pm 0.24 ~\% $ &  $ 1.35 \pm 0.01~\% $  \\ \hline
 
 \end{tabular}
 \caption{Preselection $t\overline{t}\rightarrow l+l$ cut flow}