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\begin{table}[htb] |
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\begin{center} |
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\caption{\label{tab:victorybad} |
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{\bf \color{red} Need to either update this with 38X MC, or replace it with the systematic studies varying the non-ttdil background yield and jet/met scale. } |
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{\bf \color{red} Need to either update this with 38X MC or remove it } |
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Test of the data driven method in Monte Carlo |
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under different assumptions. See text for details.} |
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\begin{tabular}{|l|c|c|c|c|c|c|c|c|} |
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\hline |
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& True $t\bar{t}$ dilepton & $t\to W\to\tau$& other SM & GEN or & Lepton $P_T$ & Z veto & \met $>$ 50& obs/pred \\ |
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& included & included & included & RECOSIM & and $\eta$ cuts & & & \\ \hline |
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& included & included & included & RECOSIM & and $\eta$ cuts & & & \\ \hline |
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1&Y & N & N & GEN & N & N & N & 1.90 \\ |
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2&Y & N & N & GEN & Y & N & N & 1.64 \\ |
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3&Y & N & N & GEN & Y & Y & N & 1.59 \\ |
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5&Y & N & N & RECOSIM & Y & Y & Y & 1.51 \\ |
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6&Y & Y & N & RECOSIM & Y & Y & Y & 1.58 \\ |
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7&Y & Y & Y & RECOSIM & Y & Y & Y & 1.38 \\ |
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%%%NOTE: updated value 1.18 -> 1.46 since 2/3 DY events have been removed by updated analysis selections, |
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%%%dpt/pt cut and general lepton veto |
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\hline |
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\end{tabular} |
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\end{center} |
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\end{table} |
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|
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|
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\begin{table}[htb] |
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\begin{center} |
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\caption{\label{tab:victorysyst} |
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{Summary of uncertainties in $K_C$ due to the MET scale and resolution uncertainty, and to backgrounds other than $t\bar{t} \to$~dilepton. |
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In the first table, `up' and `down' refer to shifting the hadronic energy scale up and down by 5\%. In the second table, the quoted value |
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refers to the amount of additional smearing of the MET, as discussed in the text. In the third table, the normalization of all backgrounds |
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other than $t\bar{t} \to$~dilepton is varied. |
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{\bf \color{ref} Should I remove `observed' and `predicted' and show only the ratio? }} |
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|
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\begin{tabular}{ lcccc } |
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\hline |
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MET scale & Predicted & Observed & Obs/pred \\ |
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\hline |
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nominal & 0.92 $ \pm $ 0.11 & 1.29 $ \pm $ 0.11 & 1.40 $ \pm $ 0.20 \\ |
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up & 0.92 $ \pm $ 0.11 & 1.53 $ \pm $ 0.12 & 1.66 $ \pm $ 0.23 \\ |
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down & 0.81 $ \pm $ 0.07 & 1.08 $ \pm $ 0.11 & 1.32 $ \pm $ 0.17 \\ |
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\hline |
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|
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\hline |
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MET smearing & Predicted & Observed & Obs/pred \\ |
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\hline |
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nominal & 0.92 $ \pm $ 0.11 & 1.29 $ \pm $ 0.11 & 1.40 $ \pm $ 0.20 \\ |
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10\% & 0.90 $ \pm $ 0.11 & 1.30 $ \pm $ 0.11 & 1.44 $ \pm $ 0.21 \\ |
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20\% & 0.84 $ \pm $ 0.07 & 1.36 $ \pm $ 0.11 & 1.61 $ \pm $ 0.19 \\ |
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30\% & 1.05 $ \pm $ 0.18 & 1.32 $ \pm $ 0.11 & 1.27 $ \pm $ 0.24 \\ |
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40\% & 0.85 $ \pm $ 0.07 & 1.37 $ \pm $ 0.11 & 1.61 $ \pm $ 0.19 \\ |
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50\% & 1.08 $ \pm $ 0.18 & 1.36 $ \pm $ 0.11 & 1.26 $ \pm $ 0.24 \\ |
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\hline |
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|
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\hline |
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non-$t\bar{t} \to$~dilepton scale factor & Predicted & Observed & Obs/pred \\ |
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\hline |
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ttdil only & 0.77 $ \pm $ 0.07 & 1.05 $ \pm $ 0.06 & 1.36 $ \pm $ 0.14 \\ |
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nominal & 0.92 $ \pm $ 0.11 & 1.29 $ \pm $ 0.11 & 1.40 $ \pm $ 0.20 \\ |
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double non-ttdil yield & 1.06 $ \pm $ 0.18 & 1.52 $ \pm $ 0.20 & 1.43 $ \pm $ 0.30 \\ |
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\hline |
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\end{tabular} |
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\end{center} |
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\end{table} |
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|
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|
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|
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The largest discrepancy between prediction and observation occurs on the first |
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line of Table~\ref{tab:victorybad}, {\em i.e.}, at the generator level with no |
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cuts. We have verified that this effect is due to the polarization of |
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We have studied this effect at the generator level using Alpgen. We find |
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that the bias is at the few percent level. |
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|
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%%%TO BE REPLACED |
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%Based on the results of Table~\ref{tab:victorybad}, we conclude that the |
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%naive data driven background estimate based on $P_T{(\ell\ell)}$ needs to |
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%be corrected by a factor of {\color{red} $ K_{\rm{fudge}} =1.2 \pm 0.3$ |
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%(We still need to settle on thie exact value of this. |
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%For the 11 pb analysis it is taken as =1.)} . The quoted |
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%uncertainty is based on the stability of the Monte Carlo tests under |
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%variations of event selections, choices of \met algorithm, etc. |
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%For example, we find that observed/predicted changes by roughly 0.1 |
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%for each 1.5\% change in the average \met response. |
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– |
|
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|
Based on the results of Table~\ref{tab:victorybad}, we conclude that the |
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< |
naive data driven background estimate based on $P_T{(\ell\ell)}$ needs to |
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< |
be corrected by a factor of $ K_C = X \pm Y$. |
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< |
The value of this correction factor as well as the systematic uncertainty |
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< |
will be assessed using 38X ttbar madgraph MC. In the following we use |
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< |
$K_C = 1$ for simplicity. Based on previous MC studies we foresee a correction |
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factor of $K_C \approx 1.2 - 1.5$, and we will assess an uncertainty |
| 260 |
< |
based on the stability of the Monte Carlo tests under |
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< |
variations of event selections, choices of \met algorithm, etc. |
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< |
For example, we find that observed/predicted changes by roughly 0.1 |
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< |
for each 1.5\% change in the average \met response. |
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> |
naive data-driven background estimate based on $P_T{(\ell\ell)}$ needs to |
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> |
be corrected by a factor of $ K_C = 1.4 \pm 0.2(stat)$. |
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|
|
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The 2 dominant sources of systematic uncertainty in $K_C$ are due to non-$t\bar{t} \to$~dilepton backgrounds, |
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and the MET scale and resolution uncertainties. The impact of non-$t\bar{t}$-dilepton background is assessed |
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by varying the yield of all backgrounds except for $t\bar{t} \to$~dilepton, as shown in Table~\ref{table_kc}. |
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The systematic is assessed as the larger of the differences between the nominal $K_C$ value and the values |
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obtained using only $t\bar{t} \to$~dilepton MC and obtained by doubling the non $t\bar{t} \to$~dilepton component, |
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giving an uncertainty of $0.04$. |
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|
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The uncertainty in $K_C$ due to the MET scale uncertainty is assessed by varying the hadronic energy scale using |
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the same method as in~\ref{} and checking how much $K_C$ changes, as summarized in Table~\ref{tab:victorysyst}. |
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This gives an uncertainty of 0.3. We also assess the impact of the MET resolution uncertainty on $K_C$ by applying |
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a random smearing to the MET. For each event, we determine the expected MET resolution based on the sumJetPt, and |
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smear the MET to simulate an increase in the resolution of 10\%, 20\%, 30\%, 40\% and 50\%. The results show that |
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$K_C$ does not depend strongly on the MET resolution and we therefore do not assess any uncertainty. |
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|
| 300 |
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Incorporating all the statistical and systematic uncertainties we find $K_C = 1.4 \pm 0.4$. |
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|
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|
\subsection{Signal Contamination} |
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\label{sec:sigcont} |
