| 1 |
|
%\section{Systematics Uncertainties on the Background Prediction} |
| 2 |
|
%\label{sec:systematics} |
| 3 |
|
|
| 4 |
– |
[DESCRIBE HERE ONE BY ONE THE UNCERTAINTIES THAT ARE PRESENT IN THE SPREADSHHET |
| 5 |
– |
FROM WHICH WE CALCULATE THE TOTAL UNCERTAINTY. WE KNOW HOW TO DO THIS |
| 6 |
– |
AND |
| 7 |
– |
WE HAVE THE TECHNOLOGY FROM THE 7 TEV ANALYSIS TO PROPAGATE ALL |
| 8 |
– |
UNCERTAINTIES |
| 9 |
– |
CORRECTLY THROUGH. WE WILL DO IT ONCE WE HAVE SETTLED ON THE |
| 10 |
– |
INDIVIDUAL PIECES WHICH ARE STILL IN FLUX] |
| 11 |
– |
|
| 4 |
|
In this Section we discuss the systematic uncertainty on the BG |
| 5 |
|
prediction. This prediction is assembled from the event |
| 6 |
|
counts in the peak region of the transverse mass distribution as |
| 34 |
|
|
| 35 |
|
\subsection{Statistical uncertainties on the event counts in the $M_T$ |
| 36 |
|
peak regions} |
| 37 |
< |
These vary between XX and XX \%, depending on the signal region |
| 37 |
> |
These vary between 2\% and 20\%, depending on the signal region |
| 38 |
|
(different |
| 39 |
|
signal regions have different \met\ requirements, thus they also have |
| 40 |
|
different $M_T$ regions used as control. |
| 44 |
|
the end. There is also an uncertainty from the finite MC event counts |
| 45 |
|
in the $M_T$ peak regions. This is also included, but it is smaller. |
| 46 |
|
|
| 47 |
+ |
Normalizing to the $M_T$ peak has the distinct advantages that |
| 48 |
+ |
uncertainties on luminosity, cross-sections, trigger efficiency, |
| 49 |
+ |
lepton ID, cancel out. |
| 50 |
+ |
For the low statistics regions with high \met requirements, the |
| 51 |
+ |
price to pay in terms of event count statistical uncertainties starts |
| 52 |
+ |
to become significant. In the future we may consider a different |
| 53 |
+ |
normalization startegy in the low statistics regions. |
| 54 |
+ |
|
| 55 |
|
\subsection{Uncertainty from the choice of $M_T$ peak region} |
| 56 |
< |
IN 7 TEV DATA WE HAD SOME SHAPE DIFFERENCES IN THE MTRANS REGION THAT |
| 57 |
< |
LED US TO CONSERVATIVELY INCLUDE THIS UNCERTAINTY. WE NEED TO LOOK |
| 58 |
< |
INTO THIS AGAIN |
| 56 |
> |
|
| 57 |
> |
This choice affects the scale factors of Table~\ref{tab:mtpeaksf}. |
| 58 |
> |
If the $M_T$ peak region is not well modelled, this would introduce an |
| 59 |
> |
uncertainty. |
| 60 |
> |
|
| 61 |
> |
We have tested this possibility by recalculating the post veto scale factors for a different |
| 62 |
> |
choice |
| 63 |
> |
of $M_T$ peak region ($40 < M_T < 100$ GeV instead of the default |
| 64 |
> |
$50 < M_T < 80$ GeV. This is shown in Table~\ref{tab:mtpeaksf2}. |
| 65 |
> |
The two results for the scale factors are very compatible. |
| 66 |
> |
We do not take any systematic uncertainty for this possible effect. |
| 67 |
> |
|
| 68 |
> |
\begin{table}[!h] |
| 69 |
> |
\begin{center} |
| 70 |
> |
{\footnotesize |
| 71 |
> |
\begin{tabular}{l||c|c|c|c|c|c|c} |
| 72 |
> |
\hline |
| 73 |
> |
Sample & SRA & SRB & SRC & SRD & SRE & SRF & SRG\\ |
| 74 |
> |
\hline |
| 75 |
> |
\hline |
| 76 |
> |
\multicolumn{8}{c}{$50 \leq \mt \leq 80$} \\ |
| 77 |
> |
\hline |
| 78 |
> |
$\mu$ pre-veto \mt-SF & $1.02 \pm 0.02$ & $0.95 \pm 0.03$ & $0.90 \pm 0.05$ & $0.98 \pm 0.08$ & $0.97 \pm 0.13$ & $0.85 \pm 0.18$ & $0.92 \pm 0.31$ \\ |
| 79 |
> |
$\mu$ post-veto \mt-SF & $1.00 \pm 0.02$ & $0.95 \pm 0.03$ & $0.91 \pm 0.05$ & $1.00 \pm 0.09$ & $0.99 \pm 0.13$ & $0.85 \pm 0.18$ & $0.96 \pm 0.31$ \\ |
| 80 |
> |
\hline |
| 81 |
> |
$\mu$ veto \mt-SF & $0.98 \pm 0.01$ & $0.99 \pm 0.01$ & $1.01 \pm 0.02$ & $1.02 \pm 0.04$ & $1.02 \pm 0.06$ & $1.00 \pm 0.09$ & $1.04 \pm 0.11$ \\ |
| 82 |
> |
\hline |
| 83 |
> |
\hline |
| 84 |
> |
e pre-veto \mt-SF & $0.95 \pm 0.02$ & $0.95 \pm 0.03$ & $0.94 \pm 0.06$ & $0.85 \pm 0.09$ & $0.84 \pm 0.13$ & $1.05 \pm 0.23$ & $1.04 \pm 0.33$ \\ |
| 85 |
> |
e post-veto \mt-SF & $0.92 \pm 0.02$ & $0.91 \pm 0.03$ & $0.91 \pm 0.06$ & $0.74 \pm 0.08$ & $0.75 \pm 0.13$ & $0.91 \pm 0.22$ & $1.01 \pm 0.33$ \\ |
| 86 |
> |
\hline |
| 87 |
> |
e veto \mt-SF & $0.97 \pm 0.01$ & $0.96 \pm 0.02$ & $0.97 \pm 0.03$ & $0.87 \pm 0.05$ & $0.89 \pm 0.08$ & $0.86 \pm 0.11$ & $0.97 \pm 0.14$ \\ |
| 88 |
> |
\hline |
| 89 |
> |
\hline |
| 90 |
> |
\multicolumn{8}{c}{$40 \leq \mt \leq 100$} \\ |
| 91 |
> |
\hline |
| 92 |
> |
$\mu$ pre-veto \mt-SF & $1.02 \pm 0.01$ & $0.97 \pm 0.02$ & $0.91 \pm 0.05$ & $0.95 \pm 0.06$ & $0.97 \pm 0.10$ & $0.80 \pm 0.14$ & $0.74 \pm 0.22$ \\ |
| 93 |
> |
$\mu$ post-veto \mt-SF & $1.00 \pm 0.01$ & $0.96 \pm 0.02$ & $0.90 \pm 0.04$ & $0.98 \pm 0.07$ & $1.00 \pm 0.11$ & $0.80 \pm 0.15$ & $0.81 \pm 0.24$ \\ |
| 94 |
> |
\hline |
| 95 |
> |
$\mu$ veto \mt-SF & $0.98 \pm 0.01$ & $0.99 \pm 0.01$ & $0.99 \pm 0.02$ & $1.03 \pm 0.03$ & $1.03 \pm 0.05$ & $1.01 \pm 0.08$ & $1.09 \pm 0.09$ \\ |
| 96 |
> |
\hline |
| 97 |
> |
\hline |
| 98 |
> |
e pre-veto \mt-SF & $0.97 \pm 0.01$ & $0.93 \pm 0.02$ & $0.94 \pm 0.04$ & $0.81 \pm 0.06$ & $0.86 \pm 0.10$ & $0.95 \pm 0.17$ & $1.06 \pm 0.26$ \\ |
| 99 |
> |
e post-veto \mt-SF & $0.94 \pm 0.01$ & $0.91 \pm 0.02$ & $0.91 \pm 0.04$ & $0.71 \pm 0.06$ & $0.82 \pm 0.10$ & $0.93 \pm 0.17$ & $1.09 \pm 0.27$ \\ |
| 100 |
> |
\hline |
| 101 |
> |
e veto \mt-SF & $0.97 \pm 0.01$ & $0.98 \pm 0.01$ & $0.97 \pm 0.02$ & $0.88 \pm 0.04$ & $0.95 \pm 0.06$ & $0.98 \pm 0.08$ & $1.03 \pm 0.09$ \\ |
| 102 |
> |
\hline |
| 103 |
> |
\end{tabular}} |
| 104 |
> |
\caption{ \mt\ peak Data/MC scale factors. The pre-veto SFs are applied to the |
| 105 |
> |
\ttdl\ sample, while the post-veto SFs are applied to the single |
| 106 |
> |
lepton samples. The veto SF is shown for comparison across channels. |
| 107 |
> |
The raw MC is used for backgrounds from rare processes. |
| 108 |
> |
The uncertainties are statistical only. |
| 109 |
> |
\label{tab:mtpeaksf2}} |
| 110 |
> |
\end{center} |
| 111 |
> |
\end{table} |
| 112 |
> |
|
| 113 |
|
|
| 114 |
|
\subsection{Uncertainty on the Wjets cross-section and the rare MC cross-sections} |
| 115 |
|
These are taken as 50\%, uncorrelated. |
| 130 |
|
These tail-to-peak ratios are described in Section~\ref{sec:ttp}. |
| 131 |
|
They are studied in CR1 and CR2. The studies are described |
| 132 |
|
in Sections~\ref{sec:cr1} and~\ref{sec:cr2}), respectively, where |
| 133 |
< |
we also give the uncertainty on the scale factors. |
| 133 |
> |
we also give the uncertainty on the scale factors. See |
| 134 |
> |
Tables~\ref{tab:cr1yields} |
| 135 |
> |
and~\ref{tab:cr2yields}, scale factors $SFR_{wjet}$ and $SFR_{top})$. |
| 136 |
|
|
| 137 |
|
\subsection{Uncertainty on extra jet radiation for dilepton |
| 138 |
|
background} |
| 140 |
|
jet distribution in |
| 141 |
|
$t\bar{t} \to$ |
| 142 |
|
dilepton MC is rescaled by the factors $K_3$ and $K_4$ to make |
| 143 |
< |
it agree with the data. The XX\% uncertainties on $K_3$ and $K_4$ |
| 143 |
> |
it agree with the data. The 3\% uncertainties on $K_3$ and $K_4$ |
| 144 |
|
comes from data/MC statistics. This |
| 145 |
< |
result directly in a XX\% uncertainty on the dilepton BG, which is by far |
| 145 |
> |
result directly in a 3\% uncertainty on the dilepton BG, which is by far |
| 146 |
|
the most important one. |
| 147 |
|
|
| 148 |
|
|
| 149 |
|
\subsection{Uncertainty on the \ttll\ Acceptance} |
| 150 |
|
|
| 151 |
+ |
[CLAUDIO: WE NEED TO DISCUSS THIS A LITTLE MORE -- THEN I CAN PUT THE |
| 152 |
+ |
WORDS IN] |
| 153 |
+ |
|
| 154 |
|
The \ttbar\ background prediction is obtained from MC, with corrections |
| 155 |
|
derived from control samples in data. The uncertainty associated with |
| 156 |
|
the theoretical modeling of the \ttbar\ production and decay is |
| 174 |
|
value for the scale used is $Q^2 = m_{\mathrm{top}}^2 + |
| 175 |
|
\sum_{\mathrm{jets}} \pt^2$. |
| 176 |
|
\item Alternative generators: Samples produced with different |
| 177 |
< |
generators include MC@NLO and Powheg (NLO generators) and |
| 119 |
< |
Pythia (LO). It may also be noted that MC@NLO uses Herwig6 for the |
| 120 |
< |
hadronisation, while POWHEG uses Pythia6. |
| 177 |
> |
generators, Powheg (our default) and Madgraph. |
| 178 |
|
\item Modeling of taus: The alternative sample does not include |
| 179 |
|
Tauola and is otherwise identical to the Powheg sample. |
| 180 |
|
This effect was studied earlier using 7~TeV samples and found to be negligible. |
| 190 |
|
\end{itemize} |
| 191 |
|
|
| 192 |
|
|
| 193 |
+ |
\begin{table}[!h] |
| 194 |
+ |
\begin{center} |
| 195 |
+ |
{\footnotesize |
| 196 |
+ |
\begin{tabular}{l||c||c|c|c|c|c|c|c} |
| 197 |
+ |
\hline |
| 198 |
+ |
Sample & Powheg & Madgraph & Mass Up & Mass Down & Scale Up & Scale Down & |
| 199 |
+ |
Match Up & Match Down \\ |
| 200 |
+ |
\hline |
| 201 |
+ |
\hline |
| 202 |
+ |
SRA & $579 \pm 10$ & $569 \pm 16$ & $591 \pm 18$ & $610 \pm 22$ & $651 \pm 22$ & $537 \pm 16$ & $578 \pm 18$ & $570 \pm 17$ \\ |
| 203 |
+ |
\hline |
| 204 |
+ |
SRB & $328 \pm 7$ & $307 \pm 11$ & $329 \pm 13$ & $348 \pm 15$ & $344 \pm 15$ & $287 \pm 10$ & $313 \pm 13$ & $307 \pm 12$ \\ |
| 205 |
+ |
\hline |
| 206 |
+ |
SRC & $111 \pm 4$ & $99 \pm 5$ & $107 \pm 7$ & $113 \pm 8$ & $124 \pm 8$ & $95 \pm 6$ & $93 \pm 6$ & $106 \pm 6$ \\ |
| 207 |
+ |
\hline |
| 208 |
+ |
SRD & $39 \pm 2$ & $35 \pm 3$ & $41 \pm 4$ & $41 \pm 5$ & $47 \pm 5$ & $33 \pm 3$ & $31 \pm 3$ & $39 \pm 4$ \\ |
| 209 |
+ |
\hline |
| 210 |
+ |
SRE & $14 \pm 1$ & $15 \pm 2$ & $17 \pm 3$ & $12 \pm 3$ & $15 \pm 3$ & $13 \pm 2$ & $12 \pm 2$ & $16 \pm 2$ \\ |
| 211 |
+ |
\hline |
| 212 |
+ |
\end{tabular}} |
| 213 |
+ |
\caption{ \ttdl\ predictions for alternative MC samples. The uncertainties are statistical only. |
| 214 |
+ |
\label{tab:ttdlalt}} |
| 215 |
+ |
\end{center} |
| 216 |
+ |
\end{table} |
| 217 |
+ |
|
| 218 |
+ |
|
| 219 |
+ |
\begin{table}[!h] |
| 220 |
+ |
\begin{center} |
| 221 |
+ |
{\footnotesize |
| 222 |
+ |
\begin{tabular}{l||c|c|c|c|c|c|c} |
| 223 |
+ |
\hline |
| 224 |
+ |
$\Delta/N$ [\%] & Madgraph & Mass Up & Mass Down & Scale Up & Scale Down & |
| 225 |
+ |
Match Up & Match Down \\ |
| 226 |
+ |
\hline |
| 227 |
+ |
\hline |
| 228 |
+ |
SRA & $2$ & $2$ & $5$ & $12$ & $7$ & $0$ & $2$ \\ |
| 229 |
+ |
\hline |
| 230 |
+ |
SRB & $6$ & $0$ & $6$ & $5$ & $12$ & $5$ & $6$ \\ |
| 231 |
+ |
\hline |
| 232 |
+ |
SRC & $10$ & $3$ & $2$ & $12$ & $14$ & $16$ & $4$ \\ |
| 233 |
+ |
\hline |
| 234 |
+ |
SRD & $10$ & $6$ & $6$ & $21$ & $15$ & $19$ & $0$ \\ |
| 235 |
+ |
\hline |
| 236 |
+ |
SRE & $6$ & $17$ & $15$ & $2$ & $12$ & $17$ & $8$ \\ |
| 237 |
+ |
\hline |
| 238 |
+ |
\end{tabular}} |
| 239 |
+ |
\caption{ Relative difference in \ttdl\ predictions for alternative MC samples. |
| 240 |
+ |
\label{tab:fracdiff}} |
| 241 |
+ |
\end{center} |
| 242 |
+ |
\end{table} |
| 243 |
+ |
|
| 244 |
+ |
|
| 245 |
+ |
\begin{table}[!h] |
| 246 |
+ |
\begin{center} |
| 247 |
+ |
{\footnotesize |
| 248 |
+ |
\begin{tabular}{l||c|c|c|c|c|c|c} |
| 249 |
+ |
\hline |
| 250 |
+ |
$N \sigma$ & Madgraph & Mass Up & Mass Down & Scale Up & Scale Down & |
| 251 |
+ |
Match Up & Match Down \\ |
| 252 |
+ |
\hline |
| 253 |
+ |
\hline |
| 254 |
+ |
SRA & $0.38$ & $0.42$ & $1.02$ & $2.34$ & $1.58$ & $0.01$ & $0.33$ \\ |
| 255 |
+ |
\hline |
| 256 |
+ |
SRB & $1.17$ & $0.07$ & $0.98$ & $0.76$ & $2.29$ & $0.78$ & $1.11$ \\ |
| 257 |
+ |
\hline |
| 258 |
+ |
SRC & $1.33$ & $0.37$ & $0.26$ & $1.24$ & $1.82$ & $1.97$ & $0.54$ \\ |
| 259 |
+ |
\hline |
| 260 |
+ |
SRD & $0.82$ & $0.46$ & $0.38$ & $1.32$ & $1.27$ & $1.47$ & $0.00$ \\ |
| 261 |
+ |
\hline |
| 262 |
+ |
SRE & $0.32$ & $0.75$ & $0.66$ & $0.07$ & $0.66$ & $0.83$ & $0.38$ \\ |
| 263 |
+ |
\hline |
| 264 |
+ |
\end{tabular}} |
| 265 |
+ |
\caption{ N $\sigma$ difference in \ttdl\ predictions for alternative MC samples. |
| 266 |
+ |
\label{tab:nsig}} |
| 267 |
+ |
\end{center} |
| 268 |
+ |
\end{table} |
| 269 |
+ |
|
| 270 |
+ |
|
| 271 |
+ |
\begin{table}[!h] |
| 272 |
+ |
\begin{center} |
| 273 |
+ |
\begin{tabular}{l||c|c|c|c} |
| 274 |
+ |
\hline |
| 275 |
+ |
Av. $\Delta$ Evt. & Alt. Gen. & $\Delta$ Mass & $\Delta$ Scale |
| 276 |
+ |
& $\Delta$ Match \\ |
| 277 |
+ |
\hline |
| 278 |
+ |
\hline |
| 279 |
+ |
SRA & $5.0$ ($1\%$) & $9.6$ ($2\%$) & $56.8$ ($10\%$) & $4.4$ ($1\%$) \\ |
| 280 |
+ |
\hline |
| 281 |
+ |
SRB & $10.4$ ($3\%$) & $9.6$ ($3\%$) & $28.2$ ($9\%$) & $2.8$ ($1\%$) \\ |
| 282 |
+ |
\hline |
| 283 |
+ |
SRC & $5.7$ ($5\%$) & $3.1$ ($3\%$) & $14.5$ ($13\%$) & $6.4$ ($6\%$) \\ |
| 284 |
+ |
\hline |
| 285 |
+ |
SRD & $1.9$ ($5\%$) & $0.1$ ($0\%$) & $6.9$ ($18\%$) & $3.6$ ($9\%$) \\ |
| 286 |
+ |
\hline |
| 287 |
+ |
SRE & $0.5$ ($3\%$) & $2.3$ ($16\%$) & $1.0$ ($7\%$) & $1.8$ ($12\%$) \\ |
| 288 |
+ |
\hline |
| 289 |
+ |
\end{tabular} |
| 290 |
+ |
\caption{ Av. difference in \ttdl\ events for alternative sample pairs. |
| 291 |
+ |
\label{tab:devt}} |
| 292 |
+ |
\end{center} |
| 293 |
+ |
\end{table} |
| 294 |
+ |
|
| 295 |
+ |
|
| 296 |
|
\begin{figure}[hbt] |
| 297 |
|
\begin{center} |
| 298 |
< |
\includegraphics[width=0.8\linewidth]{plots/n_dl_syst_comp.png} |
| 298 |
> |
\includegraphics[width=0.5\linewidth]{plots/n_dl_comp_SRA.pdf}% |
| 299 |
> |
\includegraphics[width=0.5\linewidth]{plots/n_dl_comp_SRB.pdf} |
| 300 |
> |
\includegraphics[width=0.5\linewidth]{plots/n_dl_comp_SRC.pdf}% |
| 301 |
> |
\includegraphics[width=0.5\linewidth]{plots/n_dl_comp_SRD.pdf} |
| 302 |
> |
\includegraphics[width=0.5\linewidth]{plots/n_dl_comp_SRE.pdf} |
| 303 |
|
\caption{ |
| 304 |
< |
\label{fig:ttllsyst}%\protect |
| 304 |
> |
\label{fig:ttllsyst}\protect |
| 305 |
|
Comparison of the \ttll\ central prediction with those using |
| 306 |
|
alternative MC samples. The blue band corresponds to the |
| 307 |
|
total statistical error for all data and MC samples. The |
| 454 |
|
veto performance is modeled by the Monte Carlo. This uncertainty |
| 455 |
|
only applies to the fraction of dilepton BG events that have |
| 456 |
|
a second e/$\mu$ or a one prong $\tau \to h$, with |
| 457 |
< |
$P_T > 10$ GeV in $|\eta| < 2.4$. This fraction is 1/3 (THIS WAS THE |
| 458 |
< |
7 TEV NUMBER, CHECK). The uncertainty for these events |
| 459 |
< |
is XX\% and is obtained from Tag and Probe studies of Section~\ref{sec:trkveto} |
| 460 |
< |
|
| 297 |
< |
\subsubsection{Isolated Track Veto: Tag and Probe Studies} |
| 298 |
< |
\label{sec:trkveto} |
| 299 |
< |
|
| 300 |
< |
[EVERYTHING IS 7TEV HERE, UPDATE WITH NEW RESULTS \\ |
| 301 |
< |
ADD TABLE WITH FRACTION OF EVENTS THAT HAVE A TRUE ISOLATED TRACK] |
| 457 |
> |
$P_T > 10$ GeV in $|\eta| < 2.4$. This fraction is about 1/3, see |
| 458 |
> |
Table~\ref{tab:trueisotrk}. |
| 459 |
> |
The uncertainty for these events |
| 460 |
> |
is 6\% and is obtained from Tag and Probe studies of Section~\ref{sec:trkveto} |
| 461 |
|
|
| 462 |
|
\begin{table}[!h] |
| 463 |
|
\begin{center} |
| 464 |
|
{\footnotesize |
| 465 |
< |
\begin{tabular}{l||c|c|c|c|c} |
| 465 |
> |
\begin{tabular}{l||c|c|c|c|c|c|c} |
| 466 |
|
\hline |
| 467 |
< |
Sample & SRA & SRB & SRC & SRD & SRE\\ |
| 467 |
> |
Sample & SRA & SRB & SRC & SRD & SRE & SRF & SRG \\ |
| 468 |
|
\hline |
| 469 |
|
\hline |
| 470 |
< |
Muon Frac. \ttdl\ with true iso. trk. & $0.32 \pm 0.03$ & $0.30 \pm 0.03$ & $0.32 \pm 0.06$ & $0.34 \pm 0.10$ & $0.35 \pm 0.16$ \\ |
| 470 |
> |
$\mu$ Frac. \ttdl\ with true iso. trk. & $0.32 \pm 0.03$ & $0.30 \pm 0.03$ & $0.32 \pm 0.06$ & $0.34 \pm 0.10$ & $0.35 \pm 0.16$ & $0.40 \pm 0.24$ & $0.50 \pm 0.32$ \\ |
| 471 |
|
\hline |
| 472 |
|
\hline |
| 473 |
< |
Electron Frac. \ttdl\ with true iso. trk. & $0.32 \pm 0.03$ & $0.31 \pm 0.04$ & $0.33 \pm 0.06$ & $0.38 \pm 0.11$ & $0.38 \pm 0.19$ \\ |
| 473 |
> |
e Frac. \ttdl\ with true iso. trk. & $0.32 \pm 0.03$ & $0.31 \pm 0.04$ & $0.33 \pm 0.06$ & $0.38 \pm 0.11$ & $0.38 \pm 0.19$ & $0.60 \pm 0.31$ & $0.61 \pm 0.45$ \\ |
| 474 |
|
\hline |
| 475 |
|
\end{tabular}} |
| 476 |
|
\caption{ Fraction of \ttdl\ events with a true isolated track. |
| 478 |
|
\end{center} |
| 479 |
|
\end{table} |
| 480 |
|
|
| 481 |
+ |
\subsubsection{Isolated Track Veto: Tag and Probe Studies} |
| 482 |
+ |
\label{sec:trkveto} |
| 483 |
+ |
|
| 484 |
|
|
| 485 |
|
In this section we compare the performance of the isolated track veto in data and MC using tag-and-probe studies |
| 486 |
|
with samples of Z$\to$ee and Z$\to\mu\mu$. The purpose of these studies is to demonstrate that the efficiency |
| 487 |
|
to satisfy the isolated track veto requirements is well-reproduced in the MC, since if this were not the case |
| 488 |
< |
we would need to apply a data-to-MC scale factor in order to correctly predict the \ttll\ background. This study |
| 488 |
> |
we would need to apply a data-to-MC scale factor in order to correctly |
| 489 |
> |
predict the \ttll\ background. |
| 490 |
> |
|
| 491 |
> |
This study |
| 492 |
|
addresses possible data vs. MC discrepancies for the {\bf efficiency} to identify (and reject) events with a |
| 493 |
|
second {\bf genuine} lepton (e, $\mu$, or $\tau\to$1-prong). It does not address possible data vs. MC discrepancies |
| 494 |
|
in the fake rate for rejecting events without a second genuine lepton; this is handled separately in the top normalization |
| 495 |
|
procedure by scaling the \ttlj\ contribution to match the data in the \mt\ peak after applying the isolated track veto. |
| 496 |
+ |
|
| 497 |
|
Furthermore, we test the data and MC |
| 498 |
|
isolated track veto efficiencies for electrons and muons since we are using a Z tag-and-probe technique, but we do not |
| 499 |
|
directly test the performance for hadronic tracks from $\tau$ decays. The performance for hadronic $\tau$ decay products |
| 508 |
|
leading to a total background uncertainty of less than 0.5\% (after taking into account the fraction of the total background |
| 509 |
|
due to hadronic $\tau$ decays with \pt\ $>$ 10 GeV tracks), and we hence regard this effect as neglgigible. |
| 510 |
|
|
| 511 |
< |
The tag-and-probe studies are performed in the full 2011 data sample, and compared with the DYJets madgraph sample. |
| 511 |
> |
The tag-and-probe studies are performed in the full data sample, and compared with the DYJets madgraph sample. |
| 512 |
|
All events must contain a tag-probe pair (details below) with opposite-sign and satisfying the Z mass requirement 76--106 GeV. |
| 513 |
|
We compare the distributions of absolute track isolation for probe electrons/muons in data vs. MC. The contributions to |
| 514 |
|
this isolation sum are from ambient energy in the event from underlying event, pile-up and jet activitiy, and hence do |
| 750 |
|
%END SECTION TO WRITE OUT |
| 751 |
|
|
| 752 |
|
|
| 753 |
< |
{\bf fix me: What you have written in the next paragraph does not explain how $\epsilon_{fake}$ is measured. |
| 754 |
< |
Why not measure $\epsilon_{fake}$ in the b-veto region?} |
| 753 |
> |
%{\bf fix me: What you have written in the next paragraph does not |
| 754 |
> |
%explain how $\epsilon_{fake}$ is measured. |
| 755 |
> |
%Why not measure $\epsilon_{fake}$ in the b-veto region?} |
| 756 |
|
|
| 757 |
|
%A measurement of the $\epsilon_{fake}$ in data is non-trivial. However, it is |
| 758 |
|
%possible to correct for differences in the $\epsilon_{fake}$ between data and MC by |
