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\section{Systematics Uncertainties in the Background Prediction} |
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\label{sec:systematics} |
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%\section{Systematics Uncertainties on the Background Prediction} |
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%\label{sec:systematics} |
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|
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The methodology for determining the systematics on the background |
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predictions has not changed with respect to the nominal analysis. |
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Because the template method has not changed, the same |
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systematic uncertainty is assessed on this prediction (32\%). |
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The 50\% uncertainty on the WZ and ZZ background is also unchanged. |
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The systematic uncertainty in the OF background prediction based on |
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e$\mu$ events has changed, due to the different composition of this |
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sample after vetoing events containing b-tagged jets. |
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|
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As in the nominal analysis, we do not require the e$\mu$ events |
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to satisfy the dilepton mass requirement and apply a scaling factor K, |
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extracted from MC, to account for the fraction of e$\mu$ events |
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which satisfy the dilepton mass requirement. This procedure is used |
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in order to improve the statistical precision of the OF background estimate. |
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|
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For the selection used in the nominal analysis, |
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the e$\mu$ sample is completely dominated by $t\bar{t}$ |
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events, and we observe that K is statistically consistent with constant with |
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respect to the \MET\ requirement. However, in this analysis, the $t\bar{t}$ |
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background is strongly suppressed by the b-veto, and hence the non-$t\bar{t}$ |
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backgrounds (specifically, $Z\to\tau\tau$ and VV) become more relevant. |
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At low \MET, the $Z\to\tau\tau$ background is pronounced, while $t\bar{t}$ |
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and VV dominate at high \MET\ (see App.~\ref{app:kinemu}). |
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Therefore, the sample composition changes |
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as the \MET\ requirement is varied, and as a result K depends |
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on the \MET\ requirement. |
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|
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We thus measure K in MC separately for each |
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\MET\ requirement, as displayed in Fig.~\ref{fig:kvmet} (left). |
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%The systematic uncertainty on K is determined separately for each \MET\ |
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%requirement by comparing the relative difference in K in data vs. MC. |
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The values of K used are the MC predictions |
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%and the total systematic uncertainty on the OF prediction |
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%as shown in |
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(Table \ref{fig:kvmettable}). |
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The contribution to the total OF prediction systematic uncertainty |
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from K is assessed from the ratio of K in data and MC, |
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shown in Fig.~\ref{fig:kvmet} (right). |
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The ratio is consistent with unity to roughly 17\%, |
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so we take this value as the systematic from K. |
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17\% added in quadrature with 7\% from |
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the electron to muon efficieny ratio |
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(as assessed in the inclusive analysis) |
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yields a total systematic of $\sim$18\% |
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which we round up to 20\%. |
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For \MET\ $>$ 150, there are no OF events in data inside the Z mass window |
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so we take a systematic based on the statistical uncertainty |
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of the MC prediction for K. |
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This value is 25\% for \MET\ $>$ 150 GeV and 60\% for \MET\ $>$ 200 GeV. |
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%Although we cannot check the value of K in data for \MET\ $>$ 150 |
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%because we find no OF events inside the Z mass window for this \MET\ |
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%cut, the overall OF yields with no dilepton mass requirement |
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%agree to roughly 20\% (9 data vs 7.0 $\pm$ 1.1 MC). |
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|
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|
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%Below Old |
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|
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%In reevaluating the systematics on the OF prediction, however, |
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%we observed a different behavior of K as a function of \MET\ |
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%as was seen in the inclusive analysis. |
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|
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%Recall that K is the ratio of the number of \emu\ events |
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%inside the Z window to the total number of \emu\ events. |
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%In the inclusive analysis, it is taken from \ttbar\ MC |
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%and used to scale the inclusive \emu\ yield in data. |
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%The yield scaled by K is then corrected for |
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%the $e$ vs $\mu$ efficiency difference to obtain the |
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%final OF prediction. |
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|
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%Based on the plot in figure \ref{fig:kvmet}, |
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%we choose to use a different |
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%K for each \MET\ cut and assess a systematic uncertainty |
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%on the OF prediction based on the difference between |
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%K in data and MC. |
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%The variation of K as a function of \MET\ is caused |
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%by a change in sample composition with increasing \MET. |
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%At \MET\ $<$ 60 GeV, the contribution of Z plus jets is |
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%not negligible (as it was in the inclusive analysis) |
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%because of the b veto. (See appendix \ref{app:kinemu}.) |
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%At higher \MET, \ttbar\ and diboson backgrounds dominate. |
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\subsection{Uncertainty on the \ttll\ Acceptance} |
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|
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The \ttbar\ background prediction is obtained from MC, with corrections |
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derived from control samples in data. The uncertainty associated with |
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the theoretical modeling of the \ttbar\ production and decay is |
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estimated by comparing the background predictions obtained using |
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alternative MC samples. It should be noted that the full analysis is |
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performed with the alternative samples under consideration, |
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including the derivation of the various data-to-MC scale factors. |
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The variations considered are |
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|
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\begin{itemize} |
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\item Top mass: The alternative values for the top mass differ |
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from the central value by $5~\GeV$: $m_{\mathrm{top}} = 178.5~\GeV$ and $m_{\mathrm{top}} |
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= 166.5~\GeV$. |
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\item Jet-parton matching scale: This corresponds to variations in the |
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scale at which the Matrix Element partons from Madgraph are matched |
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to Parton Shower partons from Pythia. The nominal value is |
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$x_q>20~\GeV$. The alternative values used are $x_q>10~\GeV$ and |
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$x_q>40~\GeV$. |
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\item Renormalization and factorization scale: The alternative samples |
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correspond to variations in the scale $\times 2$ and $\times 0.5$. The nominal |
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value for the scale used is $Q^2 = m_{\mathrm{top}}^2 + |
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\sum_{\mathrm{jets}} \pt^2$. |
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\item Alternative generators: Samples produced with different |
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generators include MC@NLO and Powheg (NLO generators) and |
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Pythia (LO). It may also be noted that MC@NLO uses Herwig6 for the |
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hadronisation, while POWHEG uses Pythia6. |
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\item Modeling of taus: The alternative sample does not include |
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Tauola and is otherwise identical to the Powheg sample. |
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\item The PDF uncertainty is estimated following the PDF4LHC |
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recommendations[CITE]. The events are reweighted using alternative |
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PDF sets for CT10 and MSTW2008 and the uncertainties for each are derived using the |
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alternative eigenvector variations and the ``master equation''. In |
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addition, the NNPDF2.1 set with 100 replicas. The central value is |
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determined from the mean and the uncertainty is derived from the |
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$1\sigma$ range. The overall uncertainty is derived from the envelope of the |
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alternative predictions and their uncertainties. |
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\end{itemize} |
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|
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|
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\begin{figure}[hbt] |
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\begin{center} |
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\includegraphics[width=0.8\linewidth]{plots/n_dl_syst_comp.png} |
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\caption{ |
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\label{fig:ttllsyst}%\protect |
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Comparison of the \ttll\ central prediction with those using |
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alternative MC samples. The blue band corresponds to the |
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total statistical error for all data and MC samples. The |
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alternative sample predictions are indicated by the |
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datapoints. The uncertainties on the alternative predictions |
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correspond to the uncorrelated statistical uncertainty from |
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the size of the alternative sample only.} |
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\end{center} |
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\end{figure} |
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|
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|
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|
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% |
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% |
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%The methodology for determining the systematics on the background |
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%predictions has not changed with respect to the nominal analysis. |
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%Because the template method has not changed, the same |
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%systematic uncertainty is assessed on this prediction (32\%). |
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%The 50\% uncertainty on the WZ and ZZ background is also unchanged. |
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%The systematic uncertainty in the OF background prediction based on |
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%e$\mu$ events has changed, due to the different composition of this |
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%sample after vetoing events containing b-tagged jets. |
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% |
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%As in the nominal analysis, we do not require the e$\mu$ events |
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%to satisfy the dilepton mass requirement and apply a scaling factor K, |
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%extracted from MC, to account for the fraction of e$\mu$ events |
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%which satisfy the dilepton mass requirement. This procedure is used |
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%in order to improve the statistical precision of the OF background estimate. |
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% |
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%For the selection used in the nominal analysis, |
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%the e$\mu$ sample is completely dominated by $t\bar{t}$ |
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%events, and we observe that K is statistically consistent with constant with |
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%respect to the \MET\ requirement. However, in this analysis, the $t\bar{t}$ |
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%background is strongly suppressed by the b-veto, and hence the non-$t\bar{t}$ |
| 84 |
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%backgrounds (specifically, $Z\to\tau\tau$ and VV) become more relevant. |
| 85 |
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%At low \MET, the $Z\to\tau\tau$ background is pronounced, while $t\bar{t}$ |
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%and VV dominate at high \MET\ (see App.~\ref{app:kinemu}). |
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%Therefore, the sample composition changes |
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%as the \MET\ requirement is varied, and as a result K depends |
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%on the \MET\ requirement. |
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% |
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%We thus measure K in MC separately for each |
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%\MET\ requirement, as displayed in Fig.~\ref{fig:kvmet} (left). |
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%%The systematic uncertainty on K is determined separately for each \MET\ |
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%%requirement by comparing the relative difference in K in data vs. MC. |
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%The values of K used are the MC predictions |
| 96 |
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%%and the total systematic uncertainty on the OF prediction |
| 97 |
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%%as shown in |
| 98 |
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%(Table \ref{fig:kvmettable}). |
| 99 |
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%The contribution to the total OF prediction systematic uncertainty |
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%from K is assessed from the ratio of K in data and MC, |
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%shown in Fig.~\ref{fig:kvmet} (right). |
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%The ratio is consistent with unity to roughly 17\%, |
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%so we take this value as the systematic from K. |
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%17\% added in quadrature with 7\% from |
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%the electron to muon efficieny ratio |
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%(as assessed in the inclusive analysis) |
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%yields a total systematic of $\sim$18\% |
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%which we round up to 20\%. |
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%For \MET\ $>$ 150, there are no OF events in data inside the Z mass window |
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%so we take a systematic based on the statistical uncertainty |
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%of the MC prediction for K. |
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%This value is 25\% for \MET\ $>$ 150 GeV and 60\% for \MET\ $>$ 200 GeV. |
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%%Although we cannot check the value of K in data for \MET\ $>$ 150 |
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%%because we find no OF events inside the Z mass window for this \MET\ |
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%%cut, the overall OF yields with no dilepton mass requirement |
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%%agree to roughly 20\% (9 data vs 7.0 $\pm$ 1.1 MC). |
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% |
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% |
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%%Below Old |
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% |
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%%In reevaluating the systematics on the OF prediction, however, |
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%%we observed a different behavior of K as a function of \MET\ |
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%%as was seen in the inclusive analysis. |
| 124 |
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% |
| 125 |
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%%Recall that K is the ratio of the number of \emu\ events |
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%%inside the Z window to the total number of \emu\ events. |
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%%In the inclusive analysis, it is taken from \ttbar\ MC |
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%%and used to scale the inclusive \emu\ yield in data. |
| 129 |
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%%The yield scaled by K is then corrected for |
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%%the $e$ vs $\mu$ efficiency difference to obtain the |
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%%final OF prediction. |
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% |
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%%Based on the plot in figure \ref{fig:kvmet}, |
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%%we choose to use a different |
| 135 |
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%%K for each \MET\ cut and assess a systematic uncertainty |
| 136 |
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%%on the OF prediction based on the difference between |
| 137 |
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%%K in data and MC. |
| 138 |
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%%The variation of K as a function of \MET\ is caused |
| 139 |
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%%by a change in sample composition with increasing \MET. |
| 140 |
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%%At \MET\ $<$ 60 GeV, the contribution of Z plus jets is |
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%%not negligible (as it was in the inclusive analysis) |
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%%because of the b veto. (See appendix \ref{app:kinemu}.) |
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%%At higher \MET, \ttbar\ and diboson backgrounds dominate. |
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% |
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% |
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% |
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% |
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%\begin{figure}[hbt] |
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% \begin{center} |
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% \includegraphics[width=0.48\linewidth]{plots/kvmet_data_ttbm.pdf} |
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% \includegraphics[width=0.48\linewidth]{plots/kvmet_ratio.pdf} |
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% \caption{ |
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% \label{fig:kvmet}\protect |
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% The left plot shows |
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% K as a function of \MET\ in MC (red) and data (black). |
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% The bin low edge corresponds to the \MET\ cut, and the |
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% bins are inclusive. |
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% The MC used is a sum of all SM MC used in the yield table of |
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% section \ref{sec:yields}. |
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% The right plot is the ratio of K in data to MC. |
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% The ratio is fit to a line whose slope is consistent with zero |
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% (the fit parameters are |
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% 0.9 $\pm$ 0.4 for the intercept and |
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% 0.001 $\pm$ 0.005 for the slope). |
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% } |
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% \end{center} |
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%\end{figure} |
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% |
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% |
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% |
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%\begin{table}[htb] |
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%\begin{center} |
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%\caption{\label{fig:kvmettable} The values of K used in the OF background prediction. |
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%The uncertainties shown are the total relative systematic used for the OF prediction, |
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%which is the systematic uncertainty from K added in quadrature with |
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%a 7\% uncertainty from the electron to muon efficieny ratio as assessed in the |
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%inclusive analysis. |
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%} |
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%\begin{tabular}{lcc} |
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%\hline |
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%\MET\ Cut & K & Relative Systematic \\ |
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%\hline |
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%%the met zero row is used only for normalization of the money plot. |
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%%0 & 0.1 & \\ |
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%30 & 0.12 & 20\% \\ |
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%60 & 0.13 & 20\% \\ |
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%80 & 0.12 & 20\% \\ |
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%100 & 0.12 & 20\% \\ |
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%150 & 0.09 & 25\% \\ |
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%200 & 0.06 & 60\% \\ |
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%\hline |
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%\end{tabular} |
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%\end{center} |
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%\end{table} |
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|
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|
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\subsubsection{Isolated Track Veto: Tag and Probe Studies} |
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|
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In this section we compare the performance of the isolated track veto in data and MC using tag-and-probe studies |
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with samples of Z$\to$ee and Z$\to\mu\mu$. The purpose of these studies is to demonstrate that the efficiency |
| 201 |
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to satisfy the isolated track veto requirements is well-reproduced in the MC, since if this were not the case |
| 202 |
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we would need to apply a data-to-MC scale factor in order to correctly predict the \ttll\ background. This study |
| 203 |
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addresses possible data vs. MC discrepancies for the {\bf efficiency} to identify (and reject) events with a |
| 204 |
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second {\bf genuine} lepton (e, $\mu$, or $\tau\to$1-prong). It does not address possible data vs. MC discrepancies |
| 205 |
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in the fake rate for rejecting events without a second genuine lepton; this is handled separately in the top normalization |
| 206 |
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procedure by scaling the \ttlj\ contribution to match the data in the \mt\ peak after applying the isolated track veto. |
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Furthermore, we test the data and MC |
| 208 |
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isolated track veto efficiencies for electrons and muons since we are using a Z tag-and-probe technique, but we do not |
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directly test the performance for hadronic tracks from $\tau$ decays. The performance for hadronic $\tau$ decay products |
| 210 |
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may differ from that of electrons and muons for two reasons. First, the $\tau$ may decay to a hadronic track plus one |
| 211 |
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or two $\pi^0$'s, which may decay to $\gamma\gamma$ followed by a photon conversion. As shown in Figure~\ref{fig:absiso}, |
| 212 |
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the isolation distribution for charged tracks from $\tau$ decays that are not produced in association with $\pi^0$s are |
| 213 |
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consistent with that from $\E$s and $\M$s. Since events from single prong $\tau$ decays produced in association with |
| 214 |
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$\pi^0$s comprise a small fraction of the total sample, and since the kinematics of $\tau$, $\pi^0$ and $\gamma\to e^+e^-$ |
| 215 |
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decays are well-understood, we currently demonstrate that the isolation is well-reproduced for electrons and muons only. |
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Second, hadronic tracks may undergo nuclear interactions and hence their tracks may not be reconstructed. |
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As discussed above, independent studies show that the MC reproduces the hadronic tracking efficiency within 4\%, |
| 218 |
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leading to a total background uncertainty of less than 0.5\% (after taking into account the fraction of the total background |
| 219 |
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due to hadronic $\tau$ decays with \pt\ $>$ 10 GeV tracks), and we hence regard this effect as neglgigible. |
| 220 |
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|
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The tag-and-probe studies are performed in the full 2011 data sample, and compared with the DYJets madgraph sample. |
| 222 |
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All events must contain a tag-probe pair (details below) with opposite-sign and satisfying the Z mass requirement 76--106 GeV. |
| 223 |
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We compare the distributions of absolute track isolation for probe electrons/muons in data vs. MC. The contributions to |
| 224 |
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this isolation sum are from ambient energy in the event from underlying event, pile-up and jet activitiy, and hence do |
| 225 |
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not depend on the \pt\ of the probe lepton. We therefore restrict the probe \pt\ to be $>$ 30 GeV in order to suppress |
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fake backgrounds with steeply-falling \pt\ spectra. To suppress non-Z backgrounds (in particular \ttbar) we require |
| 227 |
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\met\ $<$ 30 GeV and 0 b-tagged events. |
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The specific criteria for tags and probes for electrons and muons are: |
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|
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%We study the isolated track veto efficiency in bins of \njets. |
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%We are interested in events with at least 4 jets to emulate the hadronic activity in our signal sample. However since |
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%there are limited statistics for Z + $\geq$4 jet events, we study the isolated track performance in events with |
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|
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|
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\begin{itemize} |
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\item{Electrons} |
| 237 |
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|
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\begin{itemize} |
| 239 |
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\item{Tag criteria} |
| 240 |
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|
| 241 |
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\begin{itemize} |
| 242 |
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\item Electron passes full analysis ID/iso selection |
| 243 |
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\item \pt\ $>$ 30 GeV, $|\eta|<2.5$ |
| 244 |
+ |
|
| 245 |
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\item Matched to 1 of the 2 electron tag-and-probe triggers |
| 246 |
+ |
\begin{itemize} |
| 247 |
+ |
\item \verb=HLT_Ele17_CaloIdVT_CaloIsoVT_TrkIdT_TrkIsoVT_SC8_Mass30_v*= |
| 248 |
+ |
\item \verb=HLT_Ele17_CaloIdVT_CaloIsoVT_TrkIdT_TrkIsoVT_Ele8_Mass30_v*= |
| 249 |
+ |
\end{itemize} |
| 250 |
+ |
\end{itemize} |
| 251 |
+ |
|
| 252 |
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\item{Probe criteria} |
| 253 |
+ |
\begin{itemize} |
| 254 |
+ |
\item Electron passes full analysis ID selection |
| 255 |
+ |
\item \pt\ $>$ 30 GeV |
| 256 |
+ |
\end{itemize} |
| 257 |
+ |
\end{itemize} |
| 258 |
+ |
\item{Muons} |
| 259 |
+ |
\begin{itemize} |
| 260 |
+ |
\item{Tag criteria} |
| 261 |
+ |
\begin{itemize} |
| 262 |
+ |
\item Muon passes full analysis ID/iso selection |
| 263 |
+ |
\item \pt\ $>$ 30 GeV, $|\eta|<2.1$ |
| 264 |
+ |
\item Matched to 1 of the 2 electron tag-and-probe triggers |
| 265 |
+ |
\begin{itemize} |
| 266 |
+ |
\item \verb=HLT_IsoMu30_v*= |
| 267 |
+ |
\item \verb=HLT_IsoMu30_eta2p1_v*= |
| 268 |
+ |
\end{itemize} |
| 269 |
+ |
\end{itemize} |
| 270 |
+ |
\item{Probe criteria} |
| 271 |
+ |
\begin{itemize} |
| 272 |
+ |
\item Muon passes full analysis ID selection |
| 273 |
+ |
\item \pt\ $>$ 30 GeV |
| 274 |
+ |
\end{itemize} |
| 275 |
+ |
\end{itemize} |
| 276 |
+ |
\end{itemize} |
| 277 |
+ |
|
| 278 |
+ |
The absolute track isolation distributions for passing probes are displayed in Fig.~\ref{fig:tnp}. In general we observe |
| 279 |
+ |
good agreement between data and MC. To be more quantitative, we compare the data vs. MC efficiencies to satisfy |
| 280 |
+ |
absolute track isolation requirements varying from $>$ 1 GeV to $>$ 5 GeV, as summarized in Table~\ref{tab:isotrk}. |
| 281 |
+ |
In the $\geq$0 and $\geq$1 jet bins where the efficiencies can be tested with statistical precision, the data and MC |
| 282 |
+ |
efficiencies agree within 7\%, and we apply this as a systematic uncertainty on the isolated track veto efficiency. |
| 283 |
+ |
For the higher jet multiplicity bins the statistical precision decreases, but we do not observe any evidence for |
| 284 |
+ |
a data vs. MC discrepancy in the isolated track veto efficiency. |
| 285 |
+ |
|
| 286 |
+ |
|
| 287 |
+ |
%This is because our analysis requirement is relative track isolation $<$ 0.1, and m |
| 288 |
+ |
%This requirement is chosen because most of the tracks rejected by the isolated |
| 289 |
+ |
%track veto have a \pt\ near the 10 GeV threshold, and our analysis requirement is relative track isolation $<$ 1 GeV. |
| 290 |
|
|
| 291 |
|
\begin{figure}[hbt] |
| 292 |
|
\begin{center} |
| 293 |
< |
\includegraphics[width=0.48\linewidth]{plots/kvmet_data_ttbm.pdf} |
| 294 |
< |
\includegraphics[width=0.48\linewidth]{plots/kvmet_ratio.pdf} |
| 293 |
> |
%\includegraphics[width=0.3\linewidth]{plots/el_tkiso_0j.pdf}% |
| 294 |
> |
%\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_0j.pdf} |
| 295 |
> |
%\includegraphics[width=0.3\linewidth]{plots/el_tkiso_1j.pdf}% |
| 296 |
> |
%\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_1j.pdf} |
| 297 |
> |
%\includegraphics[width=0.3\linewidth]{plots/el_tkiso_2j.pdf}% |
| 298 |
> |
%\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_2j.pdf} |
| 299 |
> |
%\includegraphics[width=0.3\linewidth]{plots/el_tkiso_3j.pdf}% |
| 300 |
> |
%\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_3j.pdf} |
| 301 |
> |
%\includegraphics[width=0.3\linewidth]{plots/el_tkiso_4j.pdf}% |
| 302 |
> |
%\includegraphics[width=0.3\linewidth]{plots/mu_tkiso_4j.pdf} |
| 303 |
|
\caption{ |
| 304 |
< |
\label{fig:kvmet}\protect |
| 305 |
< |
The left plot shows |
| 306 |
< |
K as a function of \MET\ in MC (red) and data (black). |
| 307 |
< |
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} |
| 304 |
> |
\label{fig:tnp} Comparison of the absolute track isolation in data vs. MC for electrons (left) and muons (right) |
| 305 |
> |
for events with the \njets\ requirement varied from \njets\ $\geq$ 0 to \njets\ $\geq$ 4. |
| 306 |
> |
} |
| 307 |
> |
\end{center} |
| 308 |
|
\end{figure} |
| 309 |
|
|
| 310 |
+ |
\clearpage |
| 311 |
|
|
| 312 |
< |
|
| 111 |
< |
\begin{table}[htb] |
| 312 |
> |
\begin{table}[!ht] |
| 313 |
|
\begin{center} |
| 314 |
< |
\caption{\label{fig:kvmettable} The values of K used in the OF background prediction. |
| 315 |
< |
The uncertainties shown are the total relative systematic used for the OF prediction, |
| 316 |
< |
which is the systematic uncertainty from K added in quadrature with |
| 317 |
< |
a 7\% uncertainty from the electron to muon efficieny ratio as assessed in the |
| 318 |
< |
inclusive analysis. |
| 319 |
< |
} |
| 320 |
< |
\begin{tabular}{lcc} |
| 321 |
< |
\hline |
| 322 |
< |
\MET\ Cut & K & Relative Systematic \\ |
| 323 |
< |
\hline |
| 324 |
< |
%the met zero row is used only for normalization of the money plot. |
| 325 |
< |
%0 & 0.1 & \\ |
| 326 |
< |
30 & 0.12 & 20\% \\ |
| 327 |
< |
60 & 0.13 & 20\% \\ |
| 328 |
< |
80 & 0.12 & 20\% \\ |
| 329 |
< |
100 & 0.12 & 20\% \\ |
| 330 |
< |
150 & 0.09 & 25\% \\ |
| 331 |
< |
200 & 0.06 & 60\% \\ |
| 314 |
> |
\caption{\label{tab:isotrk} Comparison of the data vs. MC efficiencies to satisfy the indicated requirements |
| 315 |
> |
on the absolute track isolation, and the ratio of these two efficiencies. Results are indicated separately for electrons and muons and for various |
| 316 |
> |
jet multiplicity requirements.} |
| 317 |
> |
\begin{tabular}{l|l|c|c|c|c|c} |
| 318 |
> |
\hline |
| 319 |
> |
\hline |
| 320 |
> |
e + $\geq$0 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 321 |
> |
\hline |
| 322 |
> |
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 \\ |
| 323 |
> |
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 \\ |
| 324 |
> |
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 \\ |
| 325 |
> |
\hline |
| 326 |
> |
\hline |
| 327 |
> |
$\mu$ + $\geq$0 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 328 |
> |
\hline |
| 329 |
> |
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 \\ |
| 330 |
> |
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 \\ |
| 331 |
> |
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 \\ |
| 332 |
> |
\hline |
| 333 |
> |
\hline |
| 334 |
> |
e + $\geq$1 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 335 |
> |
\hline |
| 336 |
> |
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 \\ |
| 337 |
> |
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 \\ |
| 338 |
> |
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 \\ |
| 339 |
> |
\hline |
| 340 |
> |
\hline |
| 341 |
> |
$\mu$ + $\geq$1 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 342 |
> |
\hline |
| 343 |
> |
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 \\ |
| 344 |
> |
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 \\ |
| 345 |
> |
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 \\ |
| 346 |
> |
\hline |
| 347 |
> |
\hline |
| 348 |
> |
e + $\geq$2 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 349 |
> |
\hline |
| 350 |
> |
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 \\ |
| 351 |
> |
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 \\ |
| 352 |
> |
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 \\ |
| 353 |
> |
\hline |
| 354 |
> |
\hline |
| 355 |
> |
$\mu$ + $\geq$2 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 356 |
> |
\hline |
| 357 |
> |
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 \\ |
| 358 |
> |
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 \\ |
| 359 |
> |
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 \\ |
| 360 |
> |
\hline |
| 361 |
|
\hline |
| 362 |
+ |
e + $\geq$3 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 363 |
+ |
\hline |
| 364 |
+ |
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 \\ |
| 365 |
+ |
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 \\ |
| 366 |
+ |
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 \\ |
| 367 |
+ |
\hline |
| 368 |
+ |
\hline |
| 369 |
+ |
$\mu$ + $\geq$3 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 370 |
+ |
\hline |
| 371 |
+ |
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 \\ |
| 372 |
+ |
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 \\ |
| 373 |
+ |
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 \\ |
| 374 |
+ |
\hline |
| 375 |
+ |
\hline |
| 376 |
+ |
e + $\geq$4 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 377 |
+ |
\hline |
| 378 |
+ |
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 \\ |
| 379 |
+ |
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 \\ |
| 380 |
+ |
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 \\ |
| 381 |
+ |
\hline |
| 382 |
+ |
\hline |
| 383 |
+ |
$\mu$ + $\geq$4 jets & $>$ 1 GeV & $>$ 2 GeV & $>$ 3 GeV & $>$ 4 GeV & $>$ 5 GeV \\ |
| 384 |
+ |
\hline |
| 385 |
+ |
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 \\ |
| 386 |
+ |
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 \\ |
| 387 |
+ |
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 \\ |
| 388 |
+ |
\hline |
| 389 |
+ |
\hline |
| 390 |
+ |
|
| 391 |
|
\end{tabular} |
| 392 |
|
\end{center} |
| 393 |
|
\end{table} |
| 394 |
+ |
|
| 395 |
+ |
|
| 396 |
+ |
|
| 397 |
+ |
%Figure.~\ref{fig:reliso} compares the relative track isolation |
| 398 |
+ |
%for events with a track with $\pt > 10~\GeV$ in addition to a selected |
| 399 |
+ |
%muon for $\Z+4$ jet events and various \ttll\ components. The |
| 400 |
+ |
%isolation distributions show significant differences, particularly |
| 401 |
+ |
%between the leptons from a \W\ or \Z\ decay and the tracks arising |
| 402 |
+ |
%from $\tau$ decays. As can also be seen in the figure, the \pt\ |
| 403 |
+ |
%distribution for the various categories of tracks is different, where |
| 404 |
+ |
%the decay products from $\tau$s are significantly softer. Since the |
| 405 |
+ |
%\pt\ enters the denominator of the isolation definition and hence |
| 406 |
+ |
%alters the isolation variable... |
| 407 |
+ |
|
| 408 |
+ |
%\begin{figure}[hbt] |
| 409 |
+ |
% \begin{center} |
| 410 |
+ |
% \includegraphics[width=0.5\linewidth]{plots/pfiso_njets4_log.png}% |
| 411 |
+ |
% \includegraphics[width=0.5\linewidth]{plots/pfpt_njets4.png} |
| 412 |
+ |
% \caption{ |
| 413 |
+ |
% \label{fig:reliso}%\protect |
| 414 |
+ |
% Comparison of relative track isolation variable for PF cand probe in Z+jets and ttbar |
| 415 |
+ |
% Z+Jets and ttbar dilepton have similar isolation distributions |
| 416 |
+ |
% ttbar with leptonic and single prong taus tend to be less |
| 417 |
+ |
% isolated. The difference in the isolation can be attributed |
| 418 |
+ |
% to the different \pt\ distribution of the samples, since |
| 419 |
+ |
% $\tau$ decay products tend to be softer than leptons arising |
| 420 |
+ |
% from \W\ or \Z\ decays.} |
| 421 |
+ |
% \end{center} |
| 422 |
+ |
%\end{figure} |
| 423 |
+ |
|
| 424 |
+ |
% \includegraphics[width=0.5\linewidth]{plots/pfabsiso_njets4_log.png} |
| 425 |
+ |
|
| 426 |
+ |
|
| 427 |
+ |
%BEGIN SECTION TO WRITE OUT |
| 428 |
+ |
%In detail, the procedure to correct the dilepton background is: |
| 429 |
+ |
|
| 430 |
+ |
%\begin{itemize} |
| 431 |
+ |
%\item Using tag-and-probe studies, we plot the distribution of {\bf absolute} track isolation for identified probe electrons |
| 432 |
+ |
%and muons {\bf TODO: need to compare the e vs. $\mu$ track iso distributions, they might differ due to e$\to$e$\gamma$}. |
| 433 |
+ |
%\item We verify that the distribution of absolute track isolation does not depend on the \pt\ of the probe lepton. |
| 434 |
+ |
%This is due to the fact that this isolation is from ambient PU and jet activity in the event, which is uncorrelated with |
| 435 |
+ |
%the lepton \pt {\bf TODO: verify this in data and MC.}. |
| 436 |
+ |
%\item Our requirement is {\bf relative} track isolation $<$ 0.1. For a given \ttll\ MC event, we determine the \pt of the 2nd |
| 437 |
+ |
%lepton and translate this to find the corresponding requirement on the {\bf absolute} track isolation, which is simply $0.1\times$\pt. |
| 438 |
+ |
%\item We measure the efficiency to satisfy this requirement in data and MC, and define a scale-factor $SF_{\epsilon(trk)}$ which |
| 439 |
+ |
%is the ratio of the data-to-MC efficiencies. This scale-factor is applied to the \ttll\ MC event. |
| 440 |
+ |
%\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 |
| 441 |
+ |
%tracks from $\tau$ decays. Verena has showed that the absolute track isolation distribution in hadronic $\tau$ tracks is harder due |
| 442 |
+ |
%to $\pi^0\to\gamma\gamma$ with $\gamma\to e^+e^-$.} |
| 443 |
+ |
%\end{itemize} |
| 444 |
+ |
%END SECTION TO WRITE OUT |
| 445 |
+ |
|
| 446 |
+ |
|
| 447 |
+ |
{\bf fix me: What you have written in the next paragraph does not explain how $\epsilon_{fake}$ is measured. |
| 448 |
+ |
Why not measure $\epsilon_{fake}$ in the b-veto region?} |
| 449 |
+ |
|
| 450 |
+ |
A measurement of the $\epsilon_{fake}$ in data is non-trivial. However, it is |
| 451 |
+ |
possible to correct for differences in the $\epsilon_{fake}$ between data and MC by |
| 452 |
+ |
applying an additional scale factor for the single lepton background |
| 453 |
+ |
alone, using the sample in the \mt\ peak region. This scale factor is determined after applying the isolated track |
| 454 |
+ |
veto and after subtracting the \ttll\ component, corrected for the |
| 455 |
+ |
isolation efficiency derived previously. |
| 456 |
+ |
As shown in Figure~\ref{fig:vetoeffcomp}, the efficiency for selecting an |
| 457 |
+ |
isolated track in single lepton events is independent of \mt\, so the use of |
| 458 |
+ |
an overall scale factor is justified to estimate the contribution in |
| 459 |
+ |
the \mt\ tail. |
| 460 |
+ |
|
| 461 |
+ |
\begin{figure}[hbt] |
| 462 |
+ |
\begin{center} |
| 463 |
+ |
\includegraphics[width=0.5\linewidth]{plots/vetoeff_comp.png} |
| 464 |
+ |
\caption{ |
| 465 |
+ |
\label{fig:vetoeffcomp}%\protect |
| 466 |
+ |
Efficiency for selecting an isolated track comparing |
| 467 |
+ |
single lepton \ttlj\ and dilepton \ttll\ events in MC and |
| 468 |
+ |
data as a function of \mt. The |
| 469 |
+ |
efficiencies in \ttlj\ and \ttll\ exhibit no dependence on |
| 470 |
+ |
\mt\, while the data ranges between the two. This behavior |
| 471 |
+ |
is expected since the low \mt\ region is predominantly \ttlj, while the |
| 472 |
+ |
high \mt\ region contains mostly \ttll\ events.} |
| 473 |
+ |
\end{center} |
| 474 |
+ |
\end{figure} |
| 475 |
+ |
|
