| 15 |
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In 30 pb$^{-1}$ we expect $\approx$ 1 SM event in |
| 16 |
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the signal region. The expectations from the LMO |
| 17 |
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and LM1 SUSY benchmark points are 5.6 and |
| 18 |
< |
2.2 events respectively. {\color{red} I took these |
| 19 |
< |
numbers from the twiki, rescaling from 11.06 to 30/pb. |
| 20 |
< |
They seem too large...are they really right?} |
| 18 |
> |
2.2 events respectively. |
| 19 |
> |
%{\color{red} I took these |
| 20 |
> |
%numbers from the twiki, rescaling from 11.06 to 30/pb. |
| 21 |
> |
%They seem too large...are they really right?} |
| 22 |
|
|
| 23 |
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|
| 24 |
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\subsection{ABCD method} |
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\begin{center} |
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\caption{\label{tab:victorybad} 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|} |
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> |
\begin{tabular}{|l|c|c|c|c|c|c|c|c|} |
| 138 |
|
\hline |
| 139 |
< |
& True $t\bar{t}$ dilepton & $t\to W\to\tau$& other SM & GEN or & Z Veto, Lepton $P_T$ & \met $>$ 50& obs/pred \\ |
| 140 |
< |
& included & included & included & RECOSIM & and $\eta$ cuts & & \\ \hline |
| 141 |
< |
1&Y & N & N & GEN & N & N & 2.16 \\ |
| 142 |
< |
2&Y & N & N & GEN & Y & N & 1.48 \\ |
| 143 |
< |
3&Y & N & N & GEN & Y & Y & 1.52 \\ |
| 144 |
< |
4&Y & N & N & RECOSIM & Y & Y & 1.51 \\ |
| 145 |
< |
5&Y & Y & N & RECOSIM & Y & Y & 1.58 \\ |
| 146 |
< |
6&Y & Y & Y & RECOSIM & Y & Y & 1.18 \\ |
| 139 |
> |
& True $t\bar{t}$ dilepton & $t\to W\to\tau$& other SM & GEN or & Lepton $P_T$ & Z veto & \met $>$ 50& obs/pred \\ |
| 140 |
> |
& included & included & included & RECOSIM & and $\eta$ cuts & & & \\ \hline |
| 141 |
> |
1&Y & N & N & GEN & N & N & N & 1.90 \\ |
| 142 |
> |
2&Y & N & N & GEN & Y & N & N & 1.64 \\ |
| 143 |
> |
3&Y & N & N & GEN & Y & Y & N & 1.59 \\ |
| 144 |
> |
4&Y & N & N & GEN & Y & Y & Y & 1.55 \\ |
| 145 |
> |
5&Y & N & N & RECOSIM & Y & Y & Y & 1.51 \\ |
| 146 |
> |
6&Y & Y & N & RECOSIM & Y & Y & Y & 1.58 \\ |
| 147 |
> |
7&Y & Y & Y & RECOSIM & Y & Y & Y & 1.18 \\ |
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|
\hline |
| 149 |
|
\end{tabular} |
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|
\end{center} |
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cuts. We have verified that this effect is due to the polarization of |
| 157 |
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the $W$ (we remove the polarization by reweighting the events and we get |
| 158 |
|
good agreement between prediction and observation). The kinematical |
| 159 |
< |
requirements (lines 2 and 3) do not have a significant additional effect. |
| 160 |
< |
Going from GEN to RECOSIM there is a significant change in observed/predicted. |
| 161 |
< |
We have tracked this down to the fact that tcMET underestimates the true \met |
| 162 |
< |
by $\approx 4\%$\footnote{We find that observed/predicted changes by roughly 0.1 |
| 163 |
< |
for each 1.5\% change in \met response.}. Finally, contamination from non $t\bar{t}$ |
| 159 |
> |
requirements (lines 2,3,4) compensate somewhat for the effect of W polarization. |
| 160 |
> |
Going from GEN to RECOSIM, the change in observed/predicted is small. |
| 161 |
> |
% We have tracked this down to the fact that tcMET underestimates the true \met |
| 162 |
> |
% by $\approx 4\%$\footnote{We find that observed/predicted changes by roughly 0.1 |
| 163 |
> |
%for each 1.5\% change in \met response.}. |
| 164 |
> |
Finally, contamination from non $t\bar{t}$ |
| 165 |
|
events can have a significant impact on the BG prediction. The changes between |
| 166 |
< |
lines 5 and 6 of Table~\ref{tab:victorybad} is driven by only {\color{red} 3} |
| 167 |
< |
Drell Yan events that pass the \met selection. |
| 166 |
> |
lines 6 and 7 of Table~\ref{tab:victorybad} is driven by 3 |
| 167 |
> |
Drell Yan events that pass the \met selection in Monte Carlo (thus the effect |
| 168 |
> |
is statistically not well quantified). |
| 169 |
|
|
| 170 |
|
An additional source of concern is that the CMS Madgraph $t\bar{t}$ MC does |
| 171 |
|
not include effects of spin correlations between the two top quarks. |
| 173 |
|
that the bias is a the few percent level. |
| 174 |
|
|
| 175 |
|
Based on the results of Table~\ref{tab:victorybad}, we conclude that the |
| 176 |
< |
naive data driven background estimate based on $P_T{\ell\ell)}$ needs to |
| 177 |
< |
be corrected by a factor of {\color{red} $1.4 \pm 0.3$ (We need to |
| 178 |
< |
decide what this number should be)}. The quoted |
| 176 |
> |
naive data driven background estimate based on $P_T{(\ell\ell)}$ needs to |
| 177 |
> |
be corrected by a factor of {\color{red} $1.2 \pm 0.3$ (We need to talk |
| 178 |
> |
about this)} . The quoted |
| 179 |
|
uncertainty is based on the stability of the Monte Carlo tests under |
| 180 |
|
variations of event selections, choices of \met algorithm, etc. |
| 181 |
|
|
| 182 |
|
|
| 183 |
+ |
|
| 184 |
|
\subsection{Signal Contamination} |
| 185 |
|
\label{sec:sigcont} |
| 186 |
|
|
| 187 |
< |
All data-driven methods are principle subject to signal contaminations |
| 187 |
> |
All data-driven methods are in principle subject to signal contaminations |
| 188 |
|
in the control regions, and the methods described in |
| 189 |
|
Sections~\ref{sec:abcd} and~\ref{sec:victory} are not exceptions. |
| 190 |
|
Signal contamination tends to dilute the significance of a signal |
| 197 |
|
in the different control regions for the two methods. |
| 198 |
|
For example, in the extreme case of a |
| 199 |
|
new physics signal |
| 200 |
< |
with $P_T(\ell \ell) = \met$, an excess of ev ents would be seen |
| 200 |
> |
with $P_T(\ell \ell) = \met$, an excess of events would be seen |
| 201 |
|
in the ABCD method but not in the $P_T(\ell \ell)$ method. |
| 202 |
|
|
| 203 |
|
|
| 219 |
|
\hline |
| 220 |
|
SM & LM0 & BG Prediction & LM1 & BG Prediction \\ |
| 221 |
|
Background & Contribution& Including LM0 & Contribution & Including LM1 \\ \hline |
| 222 |
< |
x & x & x & x & x \\ |
| 222 |
> |
1.2 & 5.6 & 3.7 & 2.2 & 1.3 \\ |
| 223 |
|
\hline |
| 224 |
|
\end{tabular} |
| 225 |
|
\end{center} |
| 230 |
|
\caption{\label{tab:sigcontPT} Effects of signal contamination |
| 231 |
|
for the background predictions of the $P_T(\ell\ell)$ method including LM0 or |
| 232 |
|
LM1. Results |
| 233 |
< |
are normalized to 30 pb$^{-1}$.} |
| 233 |
> |
are normalized to 30 pb$^{-1}$. {\color{red} Does this BG prediction include |
| 234 |
> |
the fudge factor of 1.4 or watever because the method is not perfect.}} |
| 235 |
|
\begin{tabular}{|c||c|c||c|c|} |
| 236 |
|
\hline |
| 237 |
|
SM & LM0 & BG Prediction & LM1 & BG Prediction \\ |
| 238 |
|
Background & Contribution& Including LM0 & Contribution & Including LM1 \\ \hline |
| 239 |
< |
x & x & x & x & x \\ |
| 239 |
> |
1.2 & 5.6 & 2.2 & 2.2 & 1.5 \\ |
| 240 |
|
\hline |
| 241 |
|
\end{tabular} |
| 242 |
|
\end{center} |
