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1 < \section{Systematics Uncertainties in the Background Prediction}
2 < \label{sec:systematics}
1 > %\section{Systematics Uncertainties on the Background Prediction}
2 > %\label{sec:systematics}
3  
4 < The methodology for determining the systematics on the background
5 < predictions has not changed with respect to the nominal analysis.
6 < Because the template method has not changed, the same
7 < systematic uncertainty is assessed on this prediction (32\%).
8 < The 50\% uncertainty on the WZ and ZZ background is also unchanged.
9 < The systematic uncertainty in the OF background prediction based on
10 < e$\mu$ events has changed, due to the different composition of this
11 < sample after vetoing events containing b-tagged jets.
12 <
13 < As in the nominal analysis, we do not require the e$\mu$ events
14 < to satisfy the dilepton mass requirement and apply a scaling factor K,
15 < extracted from MC, to account for the fraction of e$\mu$ events
16 < which satisfy the dilepton mass requirement. This procedure is used
17 < in order to improve the statistical precision of the OF background estimate.
18 <
19 < For the selection used in the nominal analysis,
20 < the e$\mu$ sample is completely dominated by $t\bar{t}$
21 < events, and we observe that K is statistically consistent with constant with
22 < respect to the \MET\ requirement. However, in this analysis, the $t\bar{t}$
23 < background is strongly suppressed by the b-veto, and hence the non-$t\bar{t}$
24 < backgrounds (specifically, $Z\to\tau\tau$ and VV) become more relevant.
25 < At low \MET, the $Z\to\tau\tau$ background is pronounced, while $t\bar{t}$
26 < and VV dominate at high \MET\ (see App.~\ref{app:kinemu}).
27 < Therefore, the sample composition changes
28 < as the \MET\ requirement is varied, and as a result K depends
29 < on the \MET\ requirement.
30 <
31 < We thus measure K in MC separately for each
32 < \MET\ requirement, as displayed in Fig.~\ref{fig:kvmet} (left).
33 < %The systematic uncertainty on K is determined separately for each \MET\
34 < %requirement by comparing the relative difference in K in data vs. MC.
35 < The values of K used are the MC predictions
36 < %and the total systematic uncertainty on the OF prediction
37 < %as shown in
38 < (Table \ref{fig:kvmettable}).
39 < The contribution to the total OF prediction systematic uncertainty
40 < from K is assessed from the ratio of K in data and MC,
41 < shown in Fig.~\ref{fig:kvmet} (right).
42 < The ratio is consistent with unity to roughly 17\%,
43 < so we take this value as the systematic from K.
44 < 17\% added in quadrature with 7\% from
45 < the electron to muon efficieny ratio
46 < (as assessed in the inclusive analysis)
47 < yields a total systematic of $\sim$18\%
48 < which we round up to 20\%.
49 < For \MET\ $>$ 150, there are no OF events in data inside the Z mass window
50 < so we take a systematic based on the statistical uncertainty
51 < of the MC prediction for K.
52 < This value is 25\% for \MET\ $>$ 150 GeV and 60\% for \MET\ $>$ 200 GeV.
53 < %Although we cannot check the value of K in data for \MET\ $>$ 150
54 < %because we find no OF events inside the Z mass window for this \MET\
55 < %cut, the overall OF yields with no dilepton mass requirement
56 < %agree to roughly 20\% (9 data vs 7.0 $\pm$ 1.1 MC).
57 <
58 <
59 < %Below Old
60 <
61 < %In reevaluating the systematics on the OF prediction, however,
62 < %we observed a different behavior of K as a function of \MET\
63 < %as was seen in the inclusive analysis.
64 <
65 < %Recall that K is the ratio of the number of \emu\ events
66 < %inside the Z window to the total number of \emu\ events.
67 < %In the inclusive analysis, it is taken from \ttbar\ MC
68 < %and used to scale the inclusive \emu\ yield in data.
69 < %The yield scaled by K is then corrected for
70 < %the $e$ vs $\mu$ efficiency difference to obtain the
71 < %final OF prediction.
72 <
73 < %Based on the plot in figure \ref{fig:kvmet},
74 < %we choose to use a different
75 < %K for each \MET\ cut and assess a systematic uncertainty
76 < %on the OF prediction based on the difference between
77 < %K in data and MC.
78 < %The variation of K as a function of \MET\ is caused
79 < %by a change in sample composition with increasing \MET.
80 < %At \MET\ $<$ 60 GeV, the contribution of Z plus jets is
81 < %not negligible (as it was in the inclusive analysis)
82 < %because of the b veto. (See appendix \ref{app:kinemu}.)
83 < %At higher \MET, \ttbar\ and diboson backgrounds dominate.
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
7 > well as Monte Carlo
8 > with a number of correction factors, as described previously.
9 > The
10 > final uncertainty on the prediction is built up from the uncertainties in these
11 > individual
12 > components.
13 > The calculation is done for each signal
14 > region,
15 > for electrons and muons separately.
16 >
17 > The choice to normalizing to the peak region of $M_T$ has the
18 > advantage that some uncertainties, e.g., luminosity, cancel.
19 > It does however introduce complications because it couples
20 > some of the uncertainties in non-trivial ways.  For example,
21 > the primary effect of an uncertainty on the rare MC cross-section
22 > is to introduce an uncertainty in the rare MC background estimate
23 > which comes entirely from MC.   But this uncertainty also affects,
24 > for example,
25 > the $t\bar{t} \to$ dilepton BG estimate because it changes the
26 > $t\bar{t}$ normalization to the peak region (because some of the
27 > events in the peak region are from rare processes).  These effects
28 > are carefully accounted for.  The contribution to the overall
29 > uncertainty from each BG source is tabulated in
30 > Section~\ref{sec:bgunc-bottomline}.
31 > First, however, we discuss the uncertainties one-by-one and we comment
32 > on their impact on the overall result, at least to first order.
33 > Second order effects, such as the one described, are also included.
34 >
35 > \subsection{Statistical uncertainties on the event counts in the $M_T$
36 > peak regions}
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.
41 > Since
42 > the major BG, eg, $t\bar{t}$ are normalized to the peak regions, this
43 > fractional uncertainty is pretty much carried through all the way to
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 >
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.  
116 + The primary effect is to introduce a 50\%
117 + uncertainty
118 + on the $W +$ jets and rare BG
119 + background predictions, respectively.  However they also
120 + have an effect on the other BGs via the $M_T$ peak normalization
121 + in a way that tends to reduce the uncertainty.  This is easy
122 + to understand: if the $W$ cross-section is increased by 50\%, then
123 + the $W$ background goes up.  But the number of $M_T$ peak events
124 + attributed to $t\bar{t}$ goes down, and since the $t\bar{t}$ BG is
125 + scaled to the number of $t\bar{t}$ events in the peak, the $t\bar{t}$
126 + BG goes down.  
127 +
128 + \subsection{Scale factors for the tail-to-peak ratios for lepton +
129 +  jets top and W events}
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.  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}
139 + As discussed in Section~\ref{sec:jetmultiplicity}, the
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 3\% uncertainties on $K_3$ and $K_4$
144 + comes from data/MC statistics.  This  
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
157 + estimated by comparing the background predictions obtained using
158 + alternative MC samples. It should be noted that the full analysis is
159 + performed with the alternative samples under consideration,
160 + including the derivation of the various data-to-MC scale factors.
161 + The variations considered are
162 +
163 + \begin{itemize}
164 + \item Top mass: The alternative values for the top mass differ
165 +  from the central value by $5~\GeV$: $m_{\mathrm{top}} = 178.5~\GeV$ and $m_{\mathrm{top}}
166 +  = 166.5~\GeV$.
167 + \item Jet-parton matching scale: This corresponds to variations in the
168 +  scale at which the Matrix Element partons from Madgraph are matched
169 +  to Parton Shower partons from Pythia. The nominal value is
170 +  $x_q>20~\GeV$. The alternative values used are $x_q>10~\GeV$ and
171 +  $x_q>40~\GeV$.
172 + \item Renormalization and factorization scale: The alternative samples
173 +  correspond to variations in the scale $\times 2$ and $\times 0.5$. The nominal
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, 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.
181 + \item The PDF uncertainty is estimated following the PDF4LHC
182 +  recommendations[CITE]. The events are reweighted using alternative
183 +  PDF sets for CT10 and MSTW2008 and the uncertainties for each are derived using the
184 +  alternative eigenvector variations and the ``master equation''. In
185 +  addition, the NNPDF2.1 set with 100 replicas. The central value is
186 +  determined from the mean and the uncertainty is derived from the
187 +  $1\sigma$ range. The overall uncertainty is derived from the envelope of the
188 +  alternative predictions and their uncertainties.
189 +  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=0.5\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
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
308 +          alternative sample predictions are indicated by the
309 +          datapoints. The uncertainties on the alternative predictions
310 +          correspond to the uncorrelated statistical uncertainty from
311 +          the size of the alternative sample only.
312 +        [TO BE UPDATED WITH THE LATEST SELECTION AND SFS]}
313 +      \end{center}
314 +    \end{figure}
315 +
316 + \clearpage
317 +
318 + %
319 + %
320 + %The methodology for determining the systematics on the background
321 + %predictions has not changed with respect to the nominal analysis.
322 + %Because the template method has not changed, the same
323 + %systematic uncertainty is assessed on this prediction (32\%).
324 + %The 50\% uncertainty on the WZ and ZZ background is also unchanged.
325 + %The systematic uncertainty in the OF background prediction based on
326 + %e$\mu$ events has changed, due to the different composition of this
327 + %sample after vetoing events containing b-tagged jets.
328 + %
329 + %As in the nominal analysis, we do not require the e$\mu$ events
330 + %to satisfy the dilepton mass requirement and apply a scaling factor K,
331 + %extracted from MC, to account for the fraction of e$\mu$ events
332 + %which satisfy the dilepton mass requirement. This procedure is used
333 + %in order to improve the statistical precision of the OF background estimate.
334 + %
335 + %For the selection used in the nominal analysis,
336 + %the e$\mu$ sample is completely dominated by $t\bar{t}$
337 + %events, and we observe that K is statistically consistent with constant with
338 + %respect to the \MET\ requirement. However, in this analysis, the $t\bar{t}$
339 + %background is strongly suppressed by the b-veto, and hence the non-$t\bar{t}$
340 + %backgrounds (specifically, $Z\to\tau\tau$ and VV) become more relevant.
341 + %At low \MET, the $Z\to\tau\tau$ background is pronounced, while $t\bar{t}$
342 + %and VV dominate at high \MET\ (see App.~\ref{app:kinemu}).
343 + %Therefore, the sample composition changes
344 + %as the \MET\ requirement is varied, and as a result K depends
345 + %on the \MET\ requirement.
346 + %
347 + %We thus measure K in MC separately for each
348 + %\MET\ requirement, as displayed in Fig.~\ref{fig:kvmet} (left).
349 + %%The systematic uncertainty on K is determined separately for each \MET\
350 + %%requirement by comparing the relative difference in K in data vs. MC.
351 + %The values of K used are the MC predictions
352 + %%and the total systematic uncertainty on the OF prediction
353 + %%as shown in
354 + %(Table \ref{fig:kvmettable}).
355 + %The contribution to the total OF prediction systematic uncertainty
356 + %from K is assessed from the ratio of K in data and MC,
357 + %shown in Fig.~\ref{fig:kvmet} (right).
358 + %The ratio is consistent with unity to roughly 17\%,
359 + %so we take this value as the systematic from K.
360 + %17\% added in quadrature with 7\% from
361 + %the electron to muon efficieny ratio
362 + %(as assessed in the inclusive analysis)
363 + %yields a total systematic of $\sim$18\%
364 + %which we round up to 20\%.
365 + %For \MET\ $>$ 150, there are no OF events in data inside the Z mass window
366 + %so we take a systematic based on the statistical uncertainty
367 + %of the MC prediction for K.
368 + %This value is 25\% for \MET\ $>$ 150 GeV and 60\% for \MET\ $>$ 200 GeV.
369 + %%Although we cannot check the value of K in data for \MET\ $>$ 150
370 + %%because we find no OF events inside the Z mass window for this \MET\
371 + %%cut, the overall OF yields with no dilepton mass requirement
372 + %%agree to roughly 20\% (9 data vs 7.0 $\pm$ 1.1 MC).
373 + %
374 + %
375 + %%Below Old
376 + %
377 + %%In reevaluating the systematics on the OF prediction, however,
378 + %%we observed a different behavior of K as a function of \MET\
379 + %%as was seen in the inclusive analysis.
380 + %
381 + %%Recall that K is the ratio of the number of \emu\ events
382 + %%inside the Z window to the total number of \emu\ events.
383 + %%In the inclusive analysis, it is taken from \ttbar\ MC
384 + %%and used to scale the inclusive \emu\ yield in data.
385 + %%The yield scaled by K is then corrected for
386 + %%the $e$ vs $\mu$ efficiency difference to obtain the
387 + %%final OF prediction.
388 + %
389 + %%Based on the plot in figure \ref{fig:kvmet},
390 + %%we choose to use a different
391 + %%K for each \MET\ cut and assess a systematic uncertainty
392 + %%on the OF prediction based on the difference between
393 + %%K in data and MC.
394 + %%The variation of K as a function of \MET\ is caused
395 + %%by a change in sample composition with increasing \MET.
396 + %%At \MET\ $<$ 60 GeV, the contribution of Z plus jets is
397 + %%not negligible (as it was in the inclusive analysis)
398 + %%because of the b veto. (See appendix \ref{app:kinemu}.)
399 + %%At higher \MET, \ttbar\ and diboson backgrounds dominate.
400 + %
401 + %
402 + %
403 + %
404 + %\begin{figure}[hbt]
405 + %  \begin{center}
406 + %       \includegraphics[width=0.48\linewidth]{plots/kvmet_data_ttbm.pdf}
407 + %       \includegraphics[width=0.48\linewidth]{plots/kvmet_ratio.pdf}
408 + %       \caption{
409 + %         \label{fig:kvmet}\protect
410 + %         The left plot shows
411 + %         K as a function of \MET\ in MC (red) and data (black).
412 + %         The bin low edge corresponds to the \MET\ cut, and the
413 + %         bins are inclusive.
414 + %         The MC used is a sum of all SM MC used in the yield table of
415 + %         section \ref{sec:yields}.
416 + %         The right plot is the ratio of K in data to MC.
417 + %         The ratio is fit to a line whose slope is consistent with zero
418 + %         (the fit parameters are
419 + %         0.9 $\pm$  0.4 for the intercept and
420 + %      0.001 $\pm$ 0.005 for the slope).
421 + %       }
422 + %  \end{center}
423 + %\end{figure}
424 + %
425 + %
426 + %
427 + %\begin{table}[htb]
428 + %\begin{center}
429 + %\caption{\label{fig:kvmettable} The values of K used in the OF background prediction.
430 + %The uncertainties shown are the total relative systematic used for the OF prediction,
431 + %which is the systematic uncertainty from K added in quadrature with
432 + %a 7\% uncertainty from the electron to muon efficieny ratio as assessed in the
433 + %inclusive analysis.
434 + %}
435 + %\begin{tabular}{lcc}
436 + %\hline
437 + %\MET\ Cut    &    K        &  Relative Systematic \\
438 + %\hline
439 + %%the met zero row is used only for normalization of the money plot.
440 + %%0    &  0.1   &        \\  
441 + %30   &  0.12  &  20\%  \\  
442 + %60   &  0.13  &  20\%  \\  
443 + %80   &  0.12  &  20\%  \\  
444 + %100  &  0.12  &  20\%  \\  
445 + %150  &  0.09  &  25\%  \\  
446 + %200  &  0.06  &  60\%  \\  
447 + %\hline
448 + %\end{tabular}
449 + %\end{center}
450 + %\end{table}
451 +
452 + \subsection{Uncertainty from the isolated track veto}
453 + This is the uncertainty associated with how well the isolated track
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 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|c|c}
466 + \hline
467 + Sample              & SRA & SRB & SRC & SRD & SRE & SRF & SRG \\
468 + \hline
469 + \hline
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 + 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.
477 + \label{tab:trueisotrk}}
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
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
500 + may differ from that of electrons and muons for two reasons. First, the $\tau$ may decay to a hadronic track plus one
501 + or two $\pi^0$'s, which may decay to $\gamma\gamma$ followed by a photon conversion. As shown in Figure~\ref{fig:absiso},
502 + the isolation distribution for charged tracks from $\tau$ decays that are not produced in association with $\pi^0$s are
503 + consistent with that from $\E$s and $\M$s. Since events from single prong $\tau$ decays produced in association with
504 + $\pi^0$s comprise a small fraction of the total sample, and since the kinematics of $\tau$, $\pi^0$ and $\gamma\to e^+e^-$
505 + decays are well-understood, we currently demonstrate that the isolation is well-reproduced for electrons and muons only.
506 + Second, hadronic tracks may undergo nuclear interactions and hence their tracks may not be reconstructed.
507 + As discussed above, independent studies show that the MC reproduces the hadronic tracking efficiency within 4\%,
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 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
515 + not depend on the \pt\ of the probe lepton. We therefore restrict the probe \pt\ to be $>$ 30 GeV in order to suppress
516 + fake backgrounds with steeply-falling \pt\ spectra. To suppress non-Z backgrounds (in particular \ttbar) we require
517 + \met\ $<$ 30 GeV and 0 b-tagged events.
518 + The specific criteria for tags and probes for electrons and muons are:
519 +
520 + %We study the isolated track veto efficiency in bins of \njets.
521 + %We are interested in events with at least 4 jets to emulate the hadronic activity in our signal sample. However since
522 + %there are limited statistics for Z + $\geq$4 jet events, we study the isolated track performance in events with
523 +
524 +
525 + \begin{itemize}
526 +  \item{Electrons}
527 +
528 +    \begin{itemize}
529 +    \item{Tag criteria}
530 +
531 +      \begin{itemize}
532 +      \item Electron passes full analysis ID/iso selection
533 +      \item \pt\ $>$ 30 GeV, $|\eta|<2.1$
534 +      \item Matched to the single electron trigger \verb=HLT_Ele27_WP80_v*=
535 +      \end{itemize}
536 +
537 +    \item{Probe criteria}
538 +      \begin{itemize}
539 +      \item Electron passes full analysis ID selection
540 +      \item \pt\ $>$ 30 GeV
541 +      \end{itemize}
542 +      \end{itemize}
543 +  \item{Muons}
544 +    \begin{itemize}
545 +    \item{Tag criteria}
546 +      \begin{itemize}
547 +      \item Muon passes full analysis ID/iso selection
548 +      \item \pt\ $>$ 30 GeV, $|\eta|<2.1$
549 +      \item Matched to 1 of the 2 single muon triggers
550 +        \begin{itemize}
551 +        \item \verb=HLT_IsoMu30_v*=
552 +        \item \verb=HLT_IsoMu30_eta2p1_v*=
553 +        \end{itemize}
554 +      \end{itemize}
555 +    \item{Probe criteria}
556 +      \begin{itemize}
557 +      \item Muon passes full analysis ID selection
558 +      \item \pt\ $>$ 30 GeV
559 +      \end{itemize}
560 +    \end{itemize}
561 + \end{itemize}
562 +
563 + The absolute track isolation distributions for passing probes are displayed in Fig.~\ref{fig:tnp}. In general we observe
564 + good agreement between data and MC. To be more quantitative, we compare the data vs. MC efficiencies to satisfy
565 + absolute track isolation requirements varying from $>$ 1 GeV to $>$ 5 GeV, as summarized in Table~\ref{tab:isotrk}.
566 + In the $\geq$0 and $\geq$1 jet bins where the efficiencies can be tested with statistical precision, the data and MC
567 + efficiencies agree within 6\%, and we apply this as a systematic uncertainty on the isolated track veto efficiency.
568 + For the higher jet multiplicity bins the statistical precision decreases, but we do not observe any evidence for
569 + a data vs. MC discrepancy in the isolated track veto efficiency.
570 +
571 +
572 + %This is because our analysis requirement is relative track isolation $<$ 0.1, and m
573 + %This requirement is chosen because most of the tracks rejected by the isolated
574 + %track veto have a \pt\ near the 10 GeV threshold, and our analysis requirement is relative track isolation $<$ 1 GeV.
575  
576   \begin{figure}[hbt]
577    \begin{center}
578 <        \includegraphics[width=0.48\linewidth]{plots/kvmet_data_ttbm.pdf}
579 <        \includegraphics[width=0.48\linewidth]{plots/kvmet_ratio.pdf}
578 >        \includegraphics[width=0.3\linewidth]{plots/el_tkiso_0j.pdf}%
579 >        \includegraphics[width=0.3\linewidth]{plots/mu_tkiso_0j.pdf}
580 >        \includegraphics[width=0.3\linewidth]{plots/el_tkiso_1j.pdf}%
581 >        \includegraphics[width=0.3\linewidth]{plots/mu_tkiso_1j.pdf}
582 >        \includegraphics[width=0.3\linewidth]{plots/el_tkiso_2j.pdf}%
583 >        \includegraphics[width=0.3\linewidth]{plots/mu_tkiso_2j.pdf}
584 >        \includegraphics[width=0.3\linewidth]{plots/el_tkiso_3j.pdf}%
585 >        \includegraphics[width=0.3\linewidth]{plots/mu_tkiso_3j.pdf}
586 >        \includegraphics[width=0.3\linewidth]{plots/el_tkiso_4j.pdf}%
587 >        \includegraphics[width=0.3\linewidth]{plots/mu_tkiso_4j.pdf}
588          \caption{
589 <          \label{fig:kvmet}\protect
590 <          The left plot shows
591 <          K as a function of \MET\ in MC (red) and data (black).
592 <          The bin low edge corresponds to the \MET\ cut, and the
97 <          bins are inclusive.
98 <          The MC used is a sum of all SM MC used in the yield table of
99 <          section \ref{sec:yields}.
100 <          The right plot is the ratio of K in data to MC.
101 <          The ratio is fit to a line whose slope is consistent with zero
102 <          (the fit parameters are
103 <          0.9 $\pm$  0.4 for the intercept and
104 <      0.001 $\pm$ 0.005 for the slope).
105 <        }
106 <  \end{center}
589 >          \label{fig:tnp} Comparison of the absolute track isolation in data vs. MC for electrons (left) and muons (right)
590 > for events with the \njets\ requirement varied from \njets\ $\geq$ 0 to \njets\ $\geq$ 4.
591 > }  
592 >      \end{center}
593   \end{figure}
594  
595 + \clearpage
596  
597 <
111 < \begin{table}[htb]
597 > \begin{table}[!ht]
598   \begin{center}
599 < \caption{\label{fig:kvmettable} The values of K used in the OF background prediction.
600 < The uncertainties shown are the total relative systematic used for the OF prediction,
601 < which is the systematic uncertainty from K added in quadrature with
602 < a 7\% uncertainty from the electron to muon efficieny ratio as assessed in the
603 < inclusive analysis.
604 < }
605 < \begin{tabular}{lcc}
606 < \hline
607 < \MET\ Cut    &    K        &  Relative Systematic \\
608 < \hline
609 < %the met zero row is used only for normalization of the money plot.
610 < %0    &  0.1   &        \\  
611 < 30   &  0.12  &  20\%  \\  
612 < 60   &  0.13  &  20\%  \\  
613 < 80   &  0.12  &  20\%  \\  
614 < 100  &  0.12  &  20\%  \\  
615 < 150  &  0.09  &  25\%  \\  
616 < 200  &  0.06  &  60\%  \\  
599 > \caption{\label{tab:isotrk} Comparison of the data vs. MC efficiencies to satisfy the indicated requirements
600 > on the absolute track isolation, and the ratio of these two efficiencies. Results are indicated separately for electrons and muons and for various
601 > jet multiplicity requirements.}
602 > \begin{tabular}{l|c|c|c|c|c}
603 >
604 > %Electrons:
605 > %Selection            : ((((((((((abs(tagAndProbeMass-91)<15)&&(qProbe*qTag<0))&&((eventSelection&1)==1))&&(abs(tag->eta())<2.1))&&(tag->pt()>30.0))&&(HLT_Ele27_WP80_tag > 0))&&(met<30))&&(nbl==0))&&((leptonSelection&8)==8))&&(probe->pt()>30))&&(drprobe<0.05)
606 > %Total MC yields        : 2497277
607 > %Total DATA yields      : 2649453
608 > %Muons:
609 > %Selection            : ((((((((((abs(tagAndProbeMass-91)<15)&&(qProbe*qTag<0))&&((eventSelection&2)==2))&&(abs(tag->eta())<2.1))&&(tag->pt()>30.0))&&(HLT_IsoMu24_tag > 0))&&(met<30))&&(nbl==0))&&((leptonSelection&65536)==65536))&&(probe->pt()>30))&&(drprobe<0.05)
610 > %Total MC yields        : 3749863
611 > %Total DATA yields      : 4210022
612 > %Info in <TCanvas::MakeDefCanvas>:  created default TCanvas with name c1
613 > %Info in <TCanvas::Print>: pdf file plots/nvtx.pdf has been created
614 >
615 > \hline
616 > \hline
617 > e + $\geq$0 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
618 > \hline
619 >      data   &  0.098 $\pm$ 0.0002   &  0.036 $\pm$ 0.0001   &  0.016 $\pm$ 0.0001   &  0.009 $\pm$ 0.0001   &  0.006 $\pm$ 0.0000  \\
620 >        mc   &  0.097 $\pm$ 0.0002   &  0.034 $\pm$ 0.0001   &  0.016 $\pm$ 0.0001   &  0.009 $\pm$ 0.0001   &  0.005 $\pm$ 0.0000  \\
621 >   data/mc   &     1.00 $\pm$ 0.00   &     1.04 $\pm$ 0.00   &     1.04 $\pm$ 0.01   &     1.03 $\pm$ 0.01   &     1.02 $\pm$ 0.01  \\
622 >
623 > \hline
624 > \hline
625 > $\mu$ + $\geq$0 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
626 > \hline
627 >      data   &  0.094 $\pm$ 0.0001   &  0.034 $\pm$ 0.0001   &  0.016 $\pm$ 0.0001   &  0.009 $\pm$ 0.0000   &  0.006 $\pm$ 0.0000  \\
628 >        mc   &  0.093 $\pm$ 0.0001   &  0.033 $\pm$ 0.0001   &  0.015 $\pm$ 0.0001   &  0.009 $\pm$ 0.0000   &  0.006 $\pm$ 0.0000  \\
629 >   data/mc   &     1.01 $\pm$ 0.00   &     1.03 $\pm$ 0.00   &     1.03 $\pm$ 0.01   &     1.03 $\pm$ 0.01   &     1.02 $\pm$ 0.01  \\
630 >
631 > \hline
632 > \hline
633 > e + $\geq$1 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
634 > \hline
635 >      data   &  0.110 $\pm$ 0.0005   &  0.044 $\pm$ 0.0003   &  0.022 $\pm$ 0.0002   &  0.014 $\pm$ 0.0002   &  0.009 $\pm$ 0.0002  \\
636 >        mc   &  0.110 $\pm$ 0.0005   &  0.042 $\pm$ 0.0003   &  0.021 $\pm$ 0.0002   &  0.013 $\pm$ 0.0002   &  0.009 $\pm$ 0.0001  \\
637 >   data/mc   &     1.00 $\pm$ 0.01   &     1.04 $\pm$ 0.01   &     1.06 $\pm$ 0.02   &     1.08 $\pm$ 0.02   &     1.06 $\pm$ 0.03  \\
638 >
639   \hline
640 + \hline
641 + $\mu$ + $\geq$1 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
642 + \hline
643 +      data   &  0.106 $\pm$ 0.0004   &  0.043 $\pm$ 0.0003   &  0.023 $\pm$ 0.0002   &  0.014 $\pm$ 0.0002   &  0.010 $\pm$ 0.0001  \\
644 +        mc   &  0.106 $\pm$ 0.0004   &  0.042 $\pm$ 0.0003   &  0.021 $\pm$ 0.0002   &  0.013 $\pm$ 0.0002   &  0.009 $\pm$ 0.0001  \\
645 +   data/mc   &     1.00 $\pm$ 0.01   &     1.04 $\pm$ 0.01   &     1.06 $\pm$ 0.01   &     1.08 $\pm$ 0.02   &     1.07 $\pm$ 0.02  \\
646 +
647 + \hline
648 + \hline
649 + e + $\geq$2 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
650 + \hline
651 +      data   &  0.117 $\pm$ 0.0012   &  0.050 $\pm$ 0.0008   &  0.026 $\pm$ 0.0006   &  0.017 $\pm$ 0.0005   &  0.012 $\pm$ 0.0004  \\
652 +        mc   &  0.120 $\pm$ 0.0012   &  0.048 $\pm$ 0.0008   &  0.025 $\pm$ 0.0006   &  0.016 $\pm$ 0.0005   &  0.011 $\pm$ 0.0004  \\
653 +   data/mc   &     0.97 $\pm$ 0.01   &     1.05 $\pm$ 0.02   &     1.05 $\pm$ 0.03   &     1.07 $\pm$ 0.04   &     1.07 $\pm$ 0.05  \\
654 +
655 + \hline
656 + \hline
657 + $\mu$ + $\geq$2 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
658 + \hline
659 +      data   &  0.111 $\pm$ 0.0010   &  0.048 $\pm$ 0.0007   &  0.026 $\pm$ 0.0005   &  0.018 $\pm$ 0.0004   &  0.013 $\pm$ 0.0004  \\
660 +        mc   &  0.115 $\pm$ 0.0010   &  0.048 $\pm$ 0.0006   &  0.025 $\pm$ 0.0005   &  0.016 $\pm$ 0.0004   &  0.012 $\pm$ 0.0003  \\
661 +   data/mc   &     0.97 $\pm$ 0.01   &     1.01 $\pm$ 0.02   &     1.04 $\pm$ 0.03   &     1.09 $\pm$ 0.04   &     1.09 $\pm$ 0.04  \\
662 +
663 + \hline
664 + \hline
665 + e + $\geq$3 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
666 + \hline
667 +      data   &  0.123 $\pm$ 0.0031   &  0.058 $\pm$ 0.0022   &  0.034 $\pm$ 0.0017   &  0.023 $\pm$ 0.0014   &  0.017 $\pm$ 0.0012  \\
668 +        mc   &  0.131 $\pm$ 0.0030   &  0.055 $\pm$ 0.0020   &  0.030 $\pm$ 0.0015   &  0.020 $\pm$ 0.0013   &  0.015 $\pm$ 0.0011  \\
669 +   data/mc   &     0.94 $\pm$ 0.03   &     1.06 $\pm$ 0.06   &     1.14 $\pm$ 0.08   &     1.16 $\pm$ 0.10   &     1.17 $\pm$ 0.12  \\
670 +
671 + \hline
672 + \hline
673 + $\mu$ + $\geq$3 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
674 + \hline
675 +      data   &  0.121 $\pm$ 0.0025   &  0.055 $\pm$ 0.0018   &  0.033 $\pm$ 0.0014   &  0.022 $\pm$ 0.0011   &  0.017 $\pm$ 0.0010  \\
676 +        mc   &  0.120 $\pm$ 0.0024   &  0.052 $\pm$ 0.0016   &  0.029 $\pm$ 0.0012   &  0.019 $\pm$ 0.0010   &  0.014 $\pm$ 0.0009  \\
677 +   data/mc   &     1.01 $\pm$ 0.03   &     1.06 $\pm$ 0.05   &     1.14 $\pm$ 0.07   &     1.14 $\pm$ 0.08   &     1.16 $\pm$ 0.10  \\
678 +
679 + \hline
680 + \hline
681 + e + $\geq$4 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
682 + \hline
683 +      data   &  0.129 $\pm$ 0.0080   &  0.070 $\pm$ 0.0061   &  0.044 $\pm$ 0.0049   &  0.031 $\pm$ 0.0042   &  0.021 $\pm$ 0.0034  \\
684 +        mc   &  0.132 $\pm$ 0.0075   &  0.059 $\pm$ 0.0053   &  0.035 $\pm$ 0.0041   &  0.025 $\pm$ 0.0035   &  0.017 $\pm$ 0.0029  \\
685 +   data/mc   &     0.98 $\pm$ 0.08   &     1.18 $\pm$ 0.15   &     1.26 $\pm$ 0.20   &     1.24 $\pm$ 0.24   &     1.18 $\pm$ 0.28  \\
686 +
687 + \hline
688 + \hline
689 + $\mu$ + $\geq$4 jets   &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
690 + \hline
691 +      data   &  0.136 $\pm$ 0.0067   &  0.064 $\pm$ 0.0048   &  0.041 $\pm$ 0.0039   &  0.029 $\pm$ 0.0033   &  0.024 $\pm$ 0.0030  \\
692 +        mc   &  0.130 $\pm$ 0.0063   &  0.065 $\pm$ 0.0046   &  0.035 $\pm$ 0.0034   &  0.020 $\pm$ 0.0026   &  0.013 $\pm$ 0.0022  \\
693 +   data/mc   &     1.04 $\pm$ 0.07   &     0.99 $\pm$ 0.10   &     1.19 $\pm$ 0.16   &     1.47 $\pm$ 0.25   &     1.81 $\pm$ 0.37  \\
694 +
695 + \hline
696 + \hline
697 +
698   \end{tabular}
699   \end{center}
700   \end{table}
701 +
702 +
703 + %Figure.~\ref{fig:reliso} compares the relative track isolation
704 + %for events with a track with $\pt > 10~\GeV$ in addition to a selected
705 + %muon for $\Z+4$ jet events and various \ttll\ components. The
706 + %isolation distributions show significant differences, particularly
707 + %between the leptons from a \W\ or \Z\ decay and the tracks arising
708 + %from $\tau$ decays. As can also be seen in the figure, the \pt\
709 + %distribution for the various categories of tracks is different, where
710 + %the decay products from $\tau$s are significantly softer. Since the
711 + %\pt\ enters the denominator of the isolation definition and hence
712 + %alters the isolation variable...
713 +
714 + %\begin{figure}[hbt]
715 + %  \begin{center}
716 + %       \includegraphics[width=0.5\linewidth]{plots/pfiso_njets4_log.png}%
717 + %       \includegraphics[width=0.5\linewidth]{plots/pfpt_njets4.png}
718 + %       \caption{
719 + %         \label{fig:reliso}%\protect
720 + %          Comparison of relative track isolation variable for PF cand probe in Z+jets and ttbar
721 + %          Z+Jets and ttbar dilepton have similar isolation distributions
722 + %          ttbar with leptonic and single prong taus tend to be less
723 + %          isolated. The difference in the isolation can be attributed
724 + %          to the different \pt\ distribution of the samples, since
725 + %          $\tau$ decay products tend to be softer than leptons arising
726 + %          from \W\ or \Z\ decays.}  
727 + %      \end{center}
728 + %\end{figure}
729 +
730 + %       \includegraphics[width=0.5\linewidth]{plots/pfabsiso_njets4_log.png}
731 +
732 +
733 + %BEGIN SECTION TO WRITE OUT
734 + %In detail, the procedure to correct the dilepton background is:
735 +
736 + %\begin{itemize}
737 + %\item Using tag-and-probe studies, we plot the distribution of {\bf absolute} track isolation for identified probe electrons
738 + %and muons {\bf TODO: need to compare the e vs. $\mu$ track iso distributions, they might differ due to e$\to$e$\gamma$}.
739 + %\item We verify that the distribution of absolute track isolation does not depend on the \pt\ of the probe lepton.
740 + %This is due to the fact that this isolation is from ambient PU and jet activity in the event, which is uncorrelated with
741 + %the lepton \pt {\bf TODO: verify this in data and MC.}.
742 + %\item Our requirement is {\bf relative} track isolation $<$ 0.1. For a given \ttll\ MC event, we determine the \pt of the 2nd
743 + %lepton and translate this to find the corresponding requirement on the {\bf absolute} track isolation, which is simply $0.1\times$\pt.
744 + %\item We measure the efficiency to satisfy this requirement in data and MC, and define a scale-factor $SF_{\epsilon(trk)}$ which
745 + %is the ratio of the data-to-MC efficiencies. This scale-factor is applied to the \ttll\ MC event.
746 + %\item {\bf THING 2 we are unsure about: we can measure this SF for electrons and for muons, but we can't measure it for hadronic
747 + %tracks from $\tau$ decays. Verena has showed that the absolute track isolation distribution in hadronic $\tau$ tracks is harder due
748 + %to $\pi^0\to\gamma\gamma$ with $\gamma\to e^+e^-$.}
749 + %\end{itemize}
750 + %END SECTION TO WRITE OUT
751 +
752 +
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
759 + %applying an additional scale factor for the single lepton background
760 + %alone, using the sample in the \mt\ peak region. This scale factor is determined after applying the isolated track
761 + %veto and after subtracting the \ttll\ component, corrected for the
762 + %isolation efficiency derived previously.
763 + %As shown in Figure~\ref{fig:vetoeffcomp}, the efficiency for selecting an
764 + %isolated track in single lepton events is independent of \mt\, so the use of
765 + %an overall scale factor is justified to estimate the contribution in
766 + %the \mt\ tail.
767 + %
768 + %\begin{figure}[hbt]
769 + %  \begin{center}
770 + %       \includegraphics[width=0.5\linewidth]{plots/vetoeff_comp.png}
771 + %       \caption{
772 + %         \label{fig:vetoeffcomp}%\protect
773 + %          Efficiency for selecting an isolated track comparing
774 + %          single lepton \ttlj\ and dilepton \ttll\ events in MC and
775 + %          data as a function of \mt. The
776 + %          efficiencies in \ttlj\ and \ttll\ exhibit no dependence on
777 + %          \mt\, while the data ranges between the two. This behavior
778 + %          is expected since the low \mt\ region is predominantly \ttlj, while the
779 + %          high \mt\ region contains mostly \ttll\ events.}  
780 + %      \end{center}
781 + %\end{figure}
782 +
783 + \subsection{Summary of uncertainties}
784 + \label{sec:bgunc-bottomline}.
785 +
786 + THIS NEEDS TO BE WRITTEN

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