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1 < \section{Systematics Uncertainties in 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.
1 > %\section{Systematics Uncertainties on the Background Prediction}
2 > %\label{sec:systematics}
3  
4 + [ADD INTRODUCTORY BLURB ON UNCERTAINTIES \\
5 + ADD COMPARISONS OF ALL THE ALTERNATIVE SAMPLES FOR ALL THE SIGNAL
6 + REGIONS \\
7 + LIST ALL THE UNCERTAINTIES INCLUDED AND THEIR VALUES]
8 +
9 + \subsection{Uncertainty on the \ttll\ Acceptance}
10 +
11 + The \ttbar\ background prediction is obtained from MC, with corrections
12 + derived from control samples in data. The uncertainty associated with
13 + the theoretical modeling of the \ttbar\ production and decay is
14 + estimated by comparing the background predictions obtained using
15 + alternative MC samples. It should be noted that the full analysis is
16 + performed with the alternative samples under consideration,
17 + including the derivation of the various data-to-MC scale factors.
18 + The variations considered are
19 +
20 + \begin{itemize}
21 + \item Top mass: The alternative values for the top mass differ
22 +  from the central value by $5~\GeV$: $m_{\mathrm{top}} = 178.5~\GeV$ and $m_{\mathrm{top}}
23 +  = 166.5~\GeV$.
24 + \item Jet-parton matching scale: This corresponds to variations in the
25 +  scale at which the Matrix Element partons from Madgraph are matched
26 +  to Parton Shower partons from Pythia. The nominal value is
27 +  $x_q>20~\GeV$. The alternative values used are $x_q>10~\GeV$ and
28 +  $x_q>40~\GeV$.
29 + \item Renormalization and factorization scale: The alternative samples
30 +  correspond to variations in the scale $\times 2$ and $\times 0.5$. The nominal
31 +  value for the scale used is $Q^2 = m_{\mathrm{top}}^2 +
32 +  \sum_{\mathrm{jets}} \pt^2$.
33 + \item Alternative generators: Samples produced with different
34 +  generators include MC@NLO and Powheg (NLO generators) and
35 +  Pythia (LO). It may also be noted that MC@NLO uses Herwig6 for the
36 +  hadronisation, while POWHEG uses Pythia6.
37 + \item Modeling of taus: The alternative sample does not include
38 +  Tauola and is otherwise identical to the Powheg sample.
39 +  This effect was studied earlier using 7~TeV samples and found to be negligible.
40 + \item The PDF uncertainty is estimated following the PDF4LHC
41 +  recommendations[CITE]. The events are reweighted using alternative
42 +  PDF sets for CT10 and MSTW2008 and the uncertainties for each are derived using the
43 +  alternative eigenvector variations and the ``master equation''. In
44 +  addition, the NNPDF2.1 set with 100 replicas. The central value is
45 +  determined from the mean and the uncertainty is derived from the
46 +  $1\sigma$ range. The overall uncertainty is derived from the envelope of the
47 +  alternative predictions and their uncertainties.
48 +  This effect was studied earlier using 7~TeV samples and found to be negligible.
49 +  \end{itemize}
50  
51  
52 + \begin{figure}[hbt]
53 +  \begin{center}
54 +        \includegraphics[width=0.8\linewidth]{plots/n_dl_syst_comp.png}
55 +        \caption{
56 +          \label{fig:ttllsyst}%\protect
57 +          Comparison of the \ttll\ central prediction with those using
58 +          alternative MC samples. The blue band corresponds to the
59 +          total statistical error for all data and MC samples. The
60 +          alternative sample predictions are indicated by the
61 +          datapoints. The uncertainties on the alternative predictions
62 +          correspond to the uncorrelated statistical uncertainty from
63 +          the size of the alternative sample only.}
64 +      \end{center}
65 +    \end{figure}
66 +
67 +
68 +
69 + %
70 + %
71 + %The methodology for determining the systematics on the background
72 + %predictions has not changed with respect to the nominal analysis.
73 + %Because the template method has not changed, the same
74 + %systematic uncertainty is assessed on this prediction (32\%).
75 + %The 50\% uncertainty on the WZ and ZZ background is also unchanged.
76 + %The systematic uncertainty in the OF background prediction based on
77 + %e$\mu$ events has changed, due to the different composition of this
78 + %sample after vetoing events containing b-tagged jets.
79 + %
80 + %As in the nominal analysis, we do not require the e$\mu$ events
81 + %to satisfy the dilepton mass requirement and apply a scaling factor K,
82 + %extracted from MC, to account for the fraction of e$\mu$ events
83 + %which satisfy the dilepton mass requirement. This procedure is used
84 + %in order to improve the statistical precision of the OF background estimate.
85 + %
86 + %For the selection used in the nominal analysis,
87 + %the e$\mu$ sample is completely dominated by $t\bar{t}$
88 + %events, and we observe that K is statistically consistent with constant with
89 + %respect to the \MET\ requirement. However, in this analysis, the $t\bar{t}$
90 + %background is strongly suppressed by the b-veto, and hence the non-$t\bar{t}$
91 + %backgrounds (specifically, $Z\to\tau\tau$ and VV) become more relevant.
92 + %At low \MET, the $Z\to\tau\tau$ background is pronounced, while $t\bar{t}$
93 + %and VV dominate at high \MET\ (see App.~\ref{app:kinemu}).
94 + %Therefore, the sample composition changes
95 + %as the \MET\ requirement is varied, and as a result K depends
96 + %on the \MET\ requirement.
97 + %
98 + %We thus measure K in MC separately for each
99 + %\MET\ requirement, as displayed in Fig.~\ref{fig:kvmet} (left).
100 + %%The systematic uncertainty on K is determined separately for each \MET\
101 + %%requirement by comparing the relative difference in K in data vs. MC.
102 + %The values of K used are the MC predictions
103 + %%and the total systematic uncertainty on the OF prediction
104 + %%as shown in
105 + %(Table \ref{fig:kvmettable}).
106 + %The contribution to the total OF prediction systematic uncertainty
107 + %from K is assessed from the ratio of K in data and MC,
108 + %shown in Fig.~\ref{fig:kvmet} (right).
109 + %The ratio is consistent with unity to roughly 17\%,
110 + %so we take this value as the systematic from K.
111 + %17\% added in quadrature with 7\% from
112 + %the electron to muon efficieny ratio
113 + %(as assessed in the inclusive analysis)
114 + %yields a total systematic of $\sim$18\%
115 + %which we round up to 20\%.
116 + %For \MET\ $>$ 150, there are no OF events in data inside the Z mass window
117 + %so we take a systematic based on the statistical uncertainty
118 + %of the MC prediction for K.
119 + %This value is 25\% for \MET\ $>$ 150 GeV and 60\% for \MET\ $>$ 200 GeV.
120 + %%Although we cannot check the value of K in data for \MET\ $>$ 150
121 + %%because we find no OF events inside the Z mass window for this \MET\
122 + %%cut, the overall OF yields with no dilepton mass requirement
123 + %%agree to roughly 20\% (9 data vs 7.0 $\pm$ 1.1 MC).
124 + %
125 + %
126 + %%Below Old
127 + %
128 + %%In reevaluating the systematics on the OF prediction, however,
129 + %%we observed a different behavior of K as a function of \MET\
130 + %%as was seen in the inclusive analysis.
131 + %
132 + %%Recall that K is the ratio of the number of \emu\ events
133 + %%inside the Z window to the total number of \emu\ events.
134 + %%In the inclusive analysis, it is taken from \ttbar\ MC
135 + %%and used to scale the inclusive \emu\ yield in data.
136 + %%The yield scaled by K is then corrected for
137 + %%the $e$ vs $\mu$ efficiency difference to obtain the
138 + %%final OF prediction.
139 + %
140 + %%Based on the plot in figure \ref{fig:kvmet},
141 + %%we choose to use a different
142 + %%K for each \MET\ cut and assess a systematic uncertainty
143 + %%on the OF prediction based on the difference between
144 + %%K in data and MC.
145 + %%The variation of K as a function of \MET\ is caused
146 + %%by a change in sample composition with increasing \MET.
147 + %%At \MET\ $<$ 60 GeV, the contribution of Z plus jets is
148 + %%not negligible (as it was in the inclusive analysis)
149 + %%because of the b veto. (See appendix \ref{app:kinemu}.)
150 + %%At higher \MET, \ttbar\ and diboson backgrounds dominate.
151 + %
152 + %
153 + %
154 + %
155 + %\begin{figure}[hbt]
156 + %  \begin{center}
157 + %       \includegraphics[width=0.48\linewidth]{plots/kvmet_data_ttbm.pdf}
158 + %       \includegraphics[width=0.48\linewidth]{plots/kvmet_ratio.pdf}
159 + %       \caption{
160 + %         \label{fig:kvmet}\protect
161 + %         The left plot shows
162 + %         K as a function of \MET\ in MC (red) and data (black).
163 + %         The bin low edge corresponds to the \MET\ cut, and the
164 + %         bins are inclusive.
165 + %         The MC used is a sum of all SM MC used in the yield table of
166 + %         section \ref{sec:yields}.
167 + %         The right plot is the ratio of K in data to MC.
168 + %         The ratio is fit to a line whose slope is consistent with zero
169 + %         (the fit parameters are
170 + %         0.9 $\pm$  0.4 for the intercept and
171 + %      0.001 $\pm$ 0.005 for the slope).
172 + %       }
173 + %  \end{center}
174 + %\end{figure}
175 + %
176 + %
177 + %
178 + %\begin{table}[htb]
179 + %\begin{center}
180 + %\caption{\label{fig:kvmettable} The values of K used in the OF background prediction.
181 + %The uncertainties shown are the total relative systematic used for the OF prediction,
182 + %which is the systematic uncertainty from K added in quadrature with
183 + %a 7\% uncertainty from the electron to muon efficieny ratio as assessed in the
184 + %inclusive analysis.
185 + %}
186 + %\begin{tabular}{lcc}
187 + %\hline
188 + %\MET\ Cut    &    K        &  Relative Systematic \\
189 + %\hline
190 + %%the met zero row is used only for normalization of the money plot.
191 + %%0    &  0.1   &        \\  
192 + %30   &  0.12  &  20\%  \\  
193 + %60   &  0.13  &  20\%  \\  
194 + %80   &  0.12  &  20\%  \\  
195 + %100  &  0.12  &  20\%  \\  
196 + %150  &  0.09  &  25\%  \\  
197 + %200  &  0.06  &  60\%  \\  
198 + %\hline
199 + %\end{tabular}
200 + %\end{center}
201 + %\end{table}
202 +
203 +
204 + \subsection{Isolated Track Veto: Tag and Probe Studies}
205 +
206 + [EVERYTHING IS 7TEV HERE, UPDATE WITH NEW RESULTS \\
207 + ADD TABLE WITH FRACTION OF EVENTS THAT HAVE A TRUE ISOLATED TRACK]
208 +
209 + In this section we compare the performance of the isolated track veto in data and MC using tag-and-probe studies
210 + with samples of Z$\to$ee and Z$\to\mu\mu$. The purpose of these studies is to demonstrate that the efficiency
211 + to satisfy the isolated track veto requirements is well-reproduced in the MC, since if this were not the case
212 + we would need to apply a data-to-MC scale factor in order to correctly predict the \ttll\ background. This study
213 + addresses possible data vs. MC discrepancies for the {\bf efficiency} to identify (and reject) events with a
214 + second {\bf genuine} lepton (e, $\mu$, or $\tau\to$1-prong). It does not address possible data vs. MC discrepancies
215 + in the fake rate for rejecting events without a second genuine lepton; this is handled separately in the top normalization
216 + procedure by scaling the \ttlj\ contribution to match the data in the \mt\ peak after applying the isolated track veto.
217 + Furthermore, we test the data and MC
218 + isolated track veto efficiencies for electrons and muons since we are using a Z tag-and-probe technique, but we do not
219 + directly test the performance for hadronic tracks from $\tau$ decays. The performance for hadronic $\tau$ decay products
220 + may differ from that of electrons and muons for two reasons. First, the $\tau$ may decay to a hadronic track plus one
221 + or two $\pi^0$'s, which may decay to $\gamma\gamma$ followed by a photon conversion. As shown in Figure~\ref{fig:absiso},
222 + the isolation distribution for charged tracks from $\tau$ decays that are not produced in association with $\pi^0$s are
223 + consistent with that from $\E$s and $\M$s. Since events from single prong $\tau$ decays produced in association with
224 + $\pi^0$s comprise a small fraction of the total sample, and since the kinematics of $\tau$, $\pi^0$ and $\gamma\to e^+e^-$
225 + decays are well-understood, we currently demonstrate that the isolation is well-reproduced for electrons and muons only.
226 + Second, hadronic tracks may undergo nuclear interactions and hence their tracks may not be reconstructed.
227 + As discussed above, independent studies show that the MC reproduces the hadronic tracking efficiency within 4\%,
228 + leading to a total background uncertainty of less than 0.5\% (after taking into account the fraction of the total background
229 + due to hadronic $\tau$ decays with \pt\ $>$ 10 GeV tracks), and we hence regard this effect as neglgigible.
230 +
231 + The tag-and-probe studies are performed in the full 2011 data sample, and compared with the DYJets madgraph sample.
232 + All events must contain a tag-probe pair (details below) with opposite-sign and satisfying the Z mass requirement 76--106 GeV.
233 + We compare the distributions of absolute track isolation for probe electrons/muons in data vs. MC. The contributions to
234 + this isolation sum are from ambient energy in the event from underlying event, pile-up and jet activitiy, and hence do
235 + not depend on the \pt\ of the probe lepton. We therefore restrict the probe \pt\ to be $>$ 30 GeV in order to suppress
236 + fake backgrounds with steeply-falling \pt\ spectra. To suppress non-Z backgrounds (in particular \ttbar) we require
237 + \met\ $<$ 30 GeV and 0 b-tagged events.
238 + The specific criteria for tags and probes for electrons and muons are:
239 +
240 + %We study the isolated track veto efficiency in bins of \njets.
241 + %We are interested in events with at least 4 jets to emulate the hadronic activity in our signal sample. However since
242 + %there are limited statistics for Z + $\geq$4 jet events, we study the isolated track performance in events with
243 +
244 +
245 + \begin{itemize}
246 +  \item{Electrons}
247 +
248 +    \begin{itemize}
249 +    \item{Tag criteria}
250 +
251 +      \begin{itemize}
252 +      \item Electron passes full analysis ID/iso selection
253 +      \item \pt\ $>$ 30 GeV, $|\eta|<2.5$
254 +
255 +      \item Matched to 1 of the 2 electron tag-and-probe triggers
256 +        \begin{itemize}
257 +        \item \verb=HLT_Ele17_CaloIdVT_CaloIsoVT_TrkIdT_TrkIsoVT_SC8_Mass30_v*=
258 +        \item \verb=HLT_Ele17_CaloIdVT_CaloIsoVT_TrkIdT_TrkIsoVT_Ele8_Mass30_v*=
259 +        \end{itemize}
260 +      \end{itemize}
261 +
262 +    \item{Probe criteria}
263 +      \begin{itemize}
264 +      \item Electron passes full analysis ID selection
265 +      \item \pt\ $>$ 30 GeV
266 +      \end{itemize}
267 +      \end{itemize}
268 +  \item{Muons}
269 +    \begin{itemize}
270 +    \item{Tag criteria}
271 +      \begin{itemize}
272 +      \item Muon passes full analysis ID/iso selection
273 +      \item \pt\ $>$ 30 GeV, $|\eta|<2.1$
274 +      \item Matched to 1 of the 2 electron tag-and-probe triggers
275 +        \begin{itemize}
276 +        \item \verb=HLT_IsoMu30_v*=
277 +        \item \verb=HLT_IsoMu30_eta2p1_v*=
278 +        \end{itemize}
279 +      \end{itemize}
280 +    \item{Probe criteria}
281 +      \begin{itemize}
282 +      \item Muon passes full analysis ID selection
283 +      \item \pt\ $>$ 30 GeV
284 +      \end{itemize}
285 +    \end{itemize}
286 + \end{itemize}
287 +
288 + The absolute track isolation distributions for passing probes are displayed in Fig.~\ref{fig:tnp}. In general we observe
289 + good agreement between data and MC. To be more quantitative, we compare the data vs. MC efficiencies to satisfy
290 + absolute track isolation requirements varying from $>$ 1 GeV to $>$ 5 GeV, as summarized in Table~\ref{tab:isotrk}.
291 + In the $\geq$0 and $\geq$1 jet bins where the efficiencies can be tested with statistical precision, the data and MC
292 + efficiencies agree within 7\%, and we apply this as a systematic uncertainty on the isolated track veto efficiency.
293 + For the higher jet multiplicity bins the statistical precision decreases, but we do not observe any evidence for
294 + a data vs. MC discrepancy in the isolated track veto efficiency.
295 +
296 +
297 + %This is because our analysis requirement is relative track isolation $<$ 0.1, and m
298 + %This requirement is chosen because most of the tracks rejected by the isolated
299 + %track veto have a \pt\ near the 10 GeV threshold, and our analysis requirement is relative track isolation $<$ 1 GeV.
300  
301   \begin{figure}[hbt]
302    \begin{center}
303 <        \includegraphics[width=0.48\linewidth]{plots/kvmet_data_ttbm.pdf}
304 <        \includegraphics[width=0.48\linewidth]{plots/kvmet_ratio.pdf}
303 >        %\includegraphics[width=0.3\linewidth]{plots/el_tkiso_0j.pdf}%
304 >        %\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_0j.pdf}
305 >        %\includegraphics[width=0.3\linewidth]{plots/el_tkiso_1j.pdf}%
306 >        %\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_1j.pdf}
307 >        %\includegraphics[width=0.3\linewidth]{plots/el_tkiso_2j.pdf}%
308 >        %\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_2j.pdf}
309 >        %\includegraphics[width=0.3\linewidth]{plots/el_tkiso_3j.pdf}%
310 >        %\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_3j.pdf}
311 >        %\includegraphics[width=0.3\linewidth]{plots/el_tkiso_4j.pdf}%
312 >        %\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_4j.pdf}
313          \caption{
314 <          \label{fig:kvmet}\protect
315 <          The left plot shows
316 <          K as a function of \MET\ in MC (red) and data (black).
317 <          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}
314 >          \label{fig:tnp} Comparison of the absolute track isolation in data vs. MC for electrons (left) and muons (right)
315 > for events with the \njets\ requirement varied from \njets\ $\geq$ 0 to \njets\ $\geq$ 4.
316 > }  
317 >      \end{center}
318   \end{figure}
319  
320 + \clearpage
321  
322 <
111 < \begin{table}[htb]
322 > \begin{table}[!ht]
323   \begin{center}
324 < \caption{\label{fig:kvmettable} The values of K used in the OF background prediction.
325 < The uncertainties shown are the total relative systematic used for the OF prediction,
326 < which is the systematic uncertainty from K added in quadrature with
327 < a 7\% uncertainty from the electron to muon efficieny ratio as assessed in the
328 < inclusive analysis.
329 < }
330 < \begin{tabular}{lcc}
331 < \hline
332 < \MET\ Cut    &    K        &  Relative Systematic \\
333 < \hline
334 < %the met zero row is used only for normalization of the money plot.
335 < %0    &  0.1   &        \\  
336 < 30   &  0.12  &  20\%  \\  
337 < 60   &  0.13  &  20\%  \\  
338 < 80   &  0.12  &  20\%  \\  
339 < 100  &  0.12  &  20\%  \\  
340 < 150  &  0.09  &  25\%  \\  
341 < 200  &  0.06  &  60\%  \\  
324 > \caption{\label{tab:isotrk} Comparison of the data vs. MC efficiencies to satisfy the indicated requirements
325 > on the absolute track isolation, and the ratio of these two efficiencies. Results are indicated separately for electrons and muons and for various
326 > jet multiplicity requirements.}
327 > \begin{tabular}{l|l|c|c|c|c|c}
328 > \hline
329 > \hline
330 > e + $\geq$0 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
331 > \hline
332 >      data   &  0.088 $\pm$ 0.0003   &  0.030 $\pm$ 0.0002   &  0.013 $\pm$ 0.0001   &  0.007 $\pm$ 0.0001   &  0.005 $\pm$ 0.0001  \\
333 >        mc   &  0.087 $\pm$ 0.0001   &  0.030 $\pm$ 0.0001   &  0.014 $\pm$ 0.0001   &  0.008 $\pm$ 0.0000   &  0.005 $\pm$ 0.0000  \\
334 >   data/mc   &     1.01 $\pm$ 0.00   &     0.99 $\pm$ 0.01   &     0.97 $\pm$ 0.01   &     0.95 $\pm$ 0.01   &     0.93 $\pm$ 0.01  \\
335 > \hline
336 > \hline
337 > $\mu$ + $\geq$0 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
338 > \hline
339 >      data   &  0.087 $\pm$ 0.0002   &  0.031 $\pm$ 0.0001   &  0.015 $\pm$ 0.0001   &  0.008 $\pm$ 0.0001   &  0.005 $\pm$ 0.0001  \\
340 >        mc   &  0.085 $\pm$ 0.0001   &  0.030 $\pm$ 0.0001   &  0.014 $\pm$ 0.0000   &  0.008 $\pm$ 0.0000   &  0.005 $\pm$ 0.0000  \\
341 >   data/mc   &     1.02 $\pm$ 0.00   &     1.06 $\pm$ 0.00   &     1.06 $\pm$ 0.01   &     1.03 $\pm$ 0.01   &     1.02 $\pm$ 0.01  \\
342 > \hline
343 > \hline
344 > e + $\geq$1 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
345 > \hline
346 >      data   &  0.099 $\pm$ 0.0008   &  0.038 $\pm$ 0.0005   &  0.019 $\pm$ 0.0004   &  0.011 $\pm$ 0.0003   &  0.008 $\pm$ 0.0002  \\
347 >        mc   &  0.100 $\pm$ 0.0004   &  0.038 $\pm$ 0.0003   &  0.019 $\pm$ 0.0002   &  0.012 $\pm$ 0.0002   &  0.008 $\pm$ 0.0001  \\
348 >   data/mc   &     0.99 $\pm$ 0.01   &     1.00 $\pm$ 0.02   &     0.99 $\pm$ 0.02   &     0.98 $\pm$ 0.03   &     0.97 $\pm$ 0.03  \\
349 > \hline
350 > \hline
351 > $\mu$ + $\geq$1 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
352 > \hline
353 >      data   &  0.100 $\pm$ 0.0006   &  0.041 $\pm$ 0.0004   &  0.022 $\pm$ 0.0003   &  0.014 $\pm$ 0.0002   &  0.010 $\pm$ 0.0002  \\
354 >        mc   &  0.099 $\pm$ 0.0004   &  0.039 $\pm$ 0.0002   &  0.020 $\pm$ 0.0002   &  0.013 $\pm$ 0.0001   &  0.009 $\pm$ 0.0001  \\
355 >   data/mc   &     1.01 $\pm$ 0.01   &     1.05 $\pm$ 0.01   &     1.05 $\pm$ 0.02   &     1.06 $\pm$ 0.02   &     1.06 $\pm$ 0.03  \\
356 > \hline
357 > \hline
358 > e + $\geq$2 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
359 > \hline
360 >      data   &  0.105 $\pm$ 0.0020   &  0.042 $\pm$ 0.0013   &  0.021 $\pm$ 0.0009   &  0.013 $\pm$ 0.0007   &  0.009 $\pm$ 0.0006  \\
361 >        mc   &  0.109 $\pm$ 0.0011   &  0.043 $\pm$ 0.0007   &  0.021 $\pm$ 0.0005   &  0.013 $\pm$ 0.0004   &  0.009 $\pm$ 0.0003  \\
362 >   data/mc   &     0.96 $\pm$ 0.02   &     0.97 $\pm$ 0.03   &     1.00 $\pm$ 0.05   &     1.01 $\pm$ 0.06   &     0.97 $\pm$ 0.08  \\
363 > \hline
364   \hline
365 + $\mu$ + $\geq$2 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
366 + \hline
367 +      data   &  0.106 $\pm$ 0.0016   &  0.045 $\pm$ 0.0011   &  0.025 $\pm$ 0.0008   &  0.016 $\pm$ 0.0007   &  0.012 $\pm$ 0.0006  \\
368 +        mc   &  0.108 $\pm$ 0.0009   &  0.044 $\pm$ 0.0006   &  0.024 $\pm$ 0.0004   &  0.016 $\pm$ 0.0004   &  0.011 $\pm$ 0.0003  \\
369 +   data/mc   &     0.98 $\pm$ 0.02   &     1.04 $\pm$ 0.03   &     1.04 $\pm$ 0.04   &     1.04 $\pm$ 0.05   &     1.06 $\pm$ 0.06  \\
370 + \hline
371 + \hline
372 + e + $\geq$3 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
373 + \hline
374 +      data   &  0.117 $\pm$ 0.0055   &  0.051 $\pm$ 0.0038   &  0.029 $\pm$ 0.0029   &  0.018 $\pm$ 0.0023   &  0.012 $\pm$ 0.0019  \\
375 +        mc   &  0.120 $\pm$ 0.0031   &  0.052 $\pm$ 0.0021   &  0.027 $\pm$ 0.0015   &  0.018 $\pm$ 0.0012   &  0.013 $\pm$ 0.0011  \\
376 +   data/mc   &     0.97 $\pm$ 0.05   &     0.99 $\pm$ 0.08   &     1.10 $\pm$ 0.13   &     1.03 $\pm$ 0.15   &     0.91 $\pm$ 0.16  \\
377 + \hline
378 + \hline
379 + $\mu$ + $\geq$3 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
380 + \hline
381 +      data   &  0.111 $\pm$ 0.0044   &  0.050 $\pm$ 0.0030   &  0.029 $\pm$ 0.0024   &  0.019 $\pm$ 0.0019   &  0.014 $\pm$ 0.0017  \\
382 +        mc   &  0.115 $\pm$ 0.0025   &  0.051 $\pm$ 0.0017   &  0.030 $\pm$ 0.0013   &  0.020 $\pm$ 0.0011   &  0.015 $\pm$ 0.0009  \\
383 +   data/mc   &     0.97 $\pm$ 0.04   &     0.97 $\pm$ 0.07   &     0.95 $\pm$ 0.09   &     0.97 $\pm$ 0.11   &     0.99 $\pm$ 0.13  \\
384 + \hline
385 + \hline
386 + e + $\geq$4 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
387 + \hline
388 +      data   &  0.113 $\pm$ 0.0148   &  0.048 $\pm$ 0.0100   &  0.033 $\pm$ 0.0083   &  0.020 $\pm$ 0.0065   &  0.017 $\pm$ 0.0062  \\
389 +        mc   &  0.146 $\pm$ 0.0092   &  0.064 $\pm$ 0.0064   &  0.034 $\pm$ 0.0048   &  0.024 $\pm$ 0.0040   &  0.021 $\pm$ 0.0037  \\
390 +   data/mc   &     0.78 $\pm$ 0.11   &     0.74 $\pm$ 0.17   &     0.96 $\pm$ 0.28   &     0.82 $\pm$ 0.30   &     0.85 $\pm$ 0.34  \\
391 + \hline
392 + \hline
393 + $\mu$ + $\geq$4 jets            &           $>$ 1 GeV   &           $>$ 2 GeV   &           $>$ 3 GeV   &           $>$ 4 GeV   &           $>$ 5 GeV  \\
394 + \hline
395 +      data   &  0.130 $\pm$ 0.0128   &  0.052 $\pm$ 0.0085   &  0.028 $\pm$ 0.0063   &  0.019 $\pm$ 0.0052   &  0.019 $\pm$ 0.0052  \\
396 +        mc   &  0.105 $\pm$ 0.0064   &  0.045 $\pm$ 0.0043   &  0.027 $\pm$ 0.0034   &  0.019 $\pm$ 0.0028   &  0.014 $\pm$ 0.0024  \\
397 +   data/mc   &     1.23 $\pm$ 0.14   &     1.18 $\pm$ 0.22   &     1.03 $\pm$ 0.27   &     1.01 $\pm$ 0.32   &     1.37 $\pm$ 0.45  \\
398 + \hline
399 + \hline
400 +
401   \end{tabular}
402   \end{center}
403   \end{table}
404 +
405 +
406 +
407 + %Figure.~\ref{fig:reliso} compares the relative track isolation
408 + %for events with a track with $\pt > 10~\GeV$ in addition to a selected
409 + %muon for $\Z+4$ jet events and various \ttll\ components. The
410 + %isolation distributions show significant differences, particularly
411 + %between the leptons from a \W\ or \Z\ decay and the tracks arising
412 + %from $\tau$ decays. As can also be seen in the figure, the \pt\
413 + %distribution for the various categories of tracks is different, where
414 + %the decay products from $\tau$s are significantly softer. Since the
415 + %\pt\ enters the denominator of the isolation definition and hence
416 + %alters the isolation variable...
417 +
418 + %\begin{figure}[hbt]
419 + %  \begin{center}
420 + %       \includegraphics[width=0.5\linewidth]{plots/pfiso_njets4_log.png}%
421 + %       \includegraphics[width=0.5\linewidth]{plots/pfpt_njets4.png}
422 + %       \caption{
423 + %         \label{fig:reliso}%\protect
424 + %          Comparison of relative track isolation variable for PF cand probe in Z+jets and ttbar
425 + %          Z+Jets and ttbar dilepton have similar isolation distributions
426 + %          ttbar with leptonic and single prong taus tend to be less
427 + %          isolated. The difference in the isolation can be attributed
428 + %          to the different \pt\ distribution of the samples, since
429 + %          $\tau$ decay products tend to be softer than leptons arising
430 + %          from \W\ or \Z\ decays.}  
431 + %      \end{center}
432 + %\end{figure}
433 +
434 + %       \includegraphics[width=0.5\linewidth]{plots/pfabsiso_njets4_log.png}
435 +
436 +
437 + %BEGIN SECTION TO WRITE OUT
438 + %In detail, the procedure to correct the dilepton background is:
439 +
440 + %\begin{itemize}
441 + %\item Using tag-and-probe studies, we plot the distribution of {\bf absolute} track isolation for identified probe electrons
442 + %and muons {\bf TODO: need to compare the e vs. $\mu$ track iso distributions, they might differ due to e$\to$e$\gamma$}.
443 + %\item We verify that the distribution of absolute track isolation does not depend on the \pt\ of the probe lepton.
444 + %This is due to the fact that this isolation is from ambient PU and jet activity in the event, which is uncorrelated with
445 + %the lepton \pt {\bf TODO: verify this in data and MC.}.
446 + %\item Our requirement is {\bf relative} track isolation $<$ 0.1. For a given \ttll\ MC event, we determine the \pt of the 2nd
447 + %lepton and translate this to find the corresponding requirement on the {\bf absolute} track isolation, which is simply $0.1\times$\pt.
448 + %\item We measure the efficiency to satisfy this requirement in data and MC, and define a scale-factor $SF_{\epsilon(trk)}$ which
449 + %is the ratio of the data-to-MC efficiencies. This scale-factor is applied to the \ttll\ MC event.
450 + %\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
451 + %tracks from $\tau$ decays. Verena has showed that the absolute track isolation distribution in hadronic $\tau$ tracks is harder due
452 + %to $\pi^0\to\gamma\gamma$ with $\gamma\to e^+e^-$.}
453 + %\end{itemize}
454 + %END SECTION TO WRITE OUT
455 +
456 +
457 + {\bf fix me: What you have written in the next paragraph does not explain how $\epsilon_{fake}$ is measured.
458 + Why not measure $\epsilon_{fake}$ in the b-veto region?}
459 +
460 + %A measurement of the $\epsilon_{fake}$ in data is non-trivial. However, it is
461 + %possible to correct for differences in the $\epsilon_{fake}$ between data and MC by
462 + %applying an additional scale factor for the single lepton background
463 + %alone, using the sample in the \mt\ peak region. This scale factor is determined after applying the isolated track
464 + %veto and after subtracting the \ttll\ component, corrected for the
465 + %isolation efficiency derived previously.
466 + %As shown in Figure~\ref{fig:vetoeffcomp}, the efficiency for selecting an
467 + %isolated track in single lepton events is independent of \mt\, so the use of
468 + %an overall scale factor is justified to estimate the contribution in
469 + %the \mt\ tail.
470 + %
471 + %\begin{figure}[hbt]
472 + %  \begin{center}
473 + %       \includegraphics[width=0.5\linewidth]{plots/vetoeff_comp.png}
474 + %       \caption{
475 + %         \label{fig:vetoeffcomp}%\protect
476 + %          Efficiency for selecting an isolated track comparing
477 + %          single lepton \ttlj\ and dilepton \ttll\ events in MC and
478 + %          data as a function of \mt. The
479 + %          efficiencies in \ttlj\ and \ttll\ exhibit no dependence on
480 + %          \mt\, while the data ranges between the two. This behavior
481 + %          is expected since the low \mt\ region is predominantly \ttlj, while the
482 + %          high \mt\ region contains mostly \ttll\ events.}  
483 + %      \end{center}
484 + %\end{figure}
485 +

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