| 7 |
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Dilepton \ttbar\ events have 2 jets from the top decays, so additional |
| 8 |
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jets from radiation or higher order contributions are required to |
| 9 |
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enter the signal sample. In this Section we develop an algorithm |
| 10 |
< |
to be applied to all \ttll\ MC samples to insure that the distribution |
| 10 |
> |
to be applied to all \ttll\ MC samples to ensure that the distribution |
| 11 |
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of extra jets is properly modelled. |
| 12 |
|
|
| 13 |
|
|
| 15 |
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events is checked in a \ttll\ control sample, |
| 16 |
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selected by requiring |
| 17 |
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\begin{itemize} |
| 18 |
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\item exactly 2 selected electrons or muons with \pt $>$ 20 GeV |
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> |
\item exactly 2 electrons or muons with \pt $>$ 20 GeV |
| 19 |
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\item \met\ $>$ 50 GeV |
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\item $\geq1$ b-tagged jet |
| 21 |
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\item Z-veto ($|m_{\ell\ell} - 91| > 15$ GeV) |
| 50 |
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It should be noted that in the case of \ttll\ events |
| 51 |
|
with a single reconstructed lepton, the other lepton may be |
| 52 |
|
mis-reconstructed as a jet. For example, a hadronic tau may be |
| 53 |
< |
mis-identified as a jet (since no $\tau$ identification is used). |
| 53 |
> |
misidentified as a jet (since no $\tau$ identification is used). |
| 54 |
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In this case only 1 additional jet from radiation may suffice for |
| 55 |
|
a \ttll\ event to enter the signal sample. As a result, both the |
| 56 |
|
samples with $\ttbar+1$ jet and $\ttbar+\ge2$ jets are relevant for |
| 134 |
|
\noindent This insures that $K_3 M_3/(M_2 + K_3 M_3 + K_4 M_4) = N_3 / |
| 135 |
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(N_2+N_3+N_4)$ and similarly for the $\geq 4$ jet bin. |
| 136 |
|
|
| 137 |
< |
Table~\ref{tab:njetskfactors} also shows the values of $K_3$ and $K_4$ when the \met\ cut in the control sample definition is changed from 50 GeV to 100 GeV and 150 GeV. |
| 137 |
> |
Table~\ref{tab:njetskfactors} also shows the values of $K_3$ and $K_4$ for different values of the \met\ cut in the control sample definition. |
| 138 |
|
% These values of $K_3$ and $K_4$ are not used in the analysis, but |
| 139 |
< |
This demonstrate that there is no statistically significant dependence of $K_3$ and $K_4$ on the \met\ cut. |
| 139 |
> |
This demonstrates that there is no statistically significant dependence of $K_3$ and $K_4$ on the \met\ cut. |
| 140 |
|
|
| 141 |
|
|
| 142 |
|
The factors $K_3$ and $K_4$ (derived with the 100 GeV \met\ cut) are applied to the \ttll\ MC throughout the |
| 147 |
|
used, the MadGraph $K_3$ and $K_4$ are used, etc. |
| 148 |
|
% |
| 149 |
|
In order to do so, it is first necessary to count the number of |
| 150 |
< |
additional jets from radiation and exclude leptons mis-identified as |
| 151 |
< |
jets. A jet is considered a mis-identified lepton if it is matched to a |
| 150 |
> |
additional jets from radiation and exclude leptons misidentified as |
| 151 |
> |
jets. A jet is considered a misidentified lepton if it is matched to a |
| 152 |
|
generator-level second lepton with sufficient energy to satisfy the jet |
| 153 |
|
\pt\ requirement ($\pt>30~\GeV$). Then \ttll\ events that need two |
| 154 |
|
radiation jets to enter our selection are scaled by $K_4$, |
| 156 |
|
|
| 157 |
|
\begin{table}[!ht] |
| 158 |
|
\begin{center} |
| 159 |
< |
\begin{tabular}{l|c|c|c} |
| 160 |
< |
\cline{2-4} |
| 161 |
< |
& \multicolumn{3}{c}{ \met\ cut for data/MC scale factors} \\ |
| 159 |
> |
{\footnotesize |
| 160 |
> |
\begin{tabular}{l|c|c|c|c|c|c} |
| 161 |
> |
\cline{2-7} |
| 162 |
> |
& \multicolumn{6}{c}{ \met\ cut for data/MC scale factors} \\ |
| 163 |
|
\hline |
| 164 |
< |
Jet Multiplicity Sample & 50 GeV & 100 GeV & 150 GeV \\ |
| 164 |
> |
Sample & 50 GeV & 100 GeV & 150 GeV & 200 GeV & 250 GeV & 300 GeV \\ |
| 165 |
|
\hline |
| 166 |
|
\hline |
| 167 |
< |
N jets $= 3$ (sensitive to $\ttbar+1$ extra jet from radiation) |
| 168 |
< |
& $K_3 = 0.98 \pm 0.02$ & $K_3 = 1.01 \pm 0.03$ & $K_3 = 1.00 \pm 0.08$ \\ |
| 169 |
< |
N jets $\ge4$ (sensitive to $\ttbar+\ge2$ extra jets from radiation) |
| 170 |
< |
& $K_4 = 0.94 \pm 0.02$ & $K_4 = 0.93 \pm 0.04$ & $K_4 = 1.00 \pm 0.08$ \\ |
| 167 |
> |
N jets $= 3$ |
| 168 |
> |
& $K_3 = 0.98 \pm 0.02$ & $K_3 = 1.01 \pm 0.03$ & $K_3 = 1.00 \pm 0.08$ & $K_3 = 1.03 \pm 0.18$ & $K_3 = 1.29 \pm 0.51$ & $K_3 = 1.58 \pm 1.23$ \\ |
| 169 |
> |
N jets $\ge4$ |
| 170 |
> |
& $K_4 = 0.94 \pm 0.02$ & $K_4 = 0.93 \pm 0.04$ & $K_4 = 1.00 \pm 0.08$ & $K_4 = 1.07 \pm 0.18$ & $K_4 = 1.30 \pm 0.48$ & $K_4 = 1.65 \pm 1.19$ \\ |
| 171 |
|
\hline |
| 172 |
< |
\end{tabular} |
| 172 |
> |
\end{tabular}} |
| 173 |
|
\caption{Data/MC scale factors used to account for differences in the |
| 174 |
|
fraction of events with additional hard jets from radiation in |
| 175 |
< |
\ttll\ events. The values derived with the 100 GeV \met\ cut are applied |
| 175 |
> |
\ttll\ events. |
| 176 |
> |
The N jets $= 3$ scale factor, $K_3$, is sensitive to $\ttbar+1$ extra jet from radiation, while |
| 177 |
> |
the N jets $\ge4$ scale factor, $K_4$, is sensitive to $\ttbar+\ge2$ extra jets from radiation. |
| 178 |
> |
The values derived with the 100 GeV \met\ cut are applied |
| 179 |
|
to the \ttll\ MC throughout the analysis. \label{tab:njetskfactors}} |
| 180 |
|
\end{center} |
| 181 |
|
\end{table} |
| 199 |
|
|
| 200 |
|
The $t\bar{t}$ MC is corrected using the $K_3$ and $K_4$ factors |
| 201 |
|
from Section~\ref{sec:jetmultiplicity}. It is also normalized to the |
| 202 |
< |
total data yield separately for the \met\ requirements of signal |
| 203 |
< |
regions A, B, C, and D. These normalization factors are listed |
| 202 |
> |
total data yield separately for the \met\ requirements of the various signal |
| 203 |
> |
regions. These normalization factors are listed |
| 204 |
|
in Table~\ref{tab:cr4mtsf} and are close to unity. |
| 205 |
|
|
| 206 |
|
The underlying \met\ and $M_T$ distributions are shown in |
