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1   \subsection{Further cross-checks}
2 < The test described in the previous Section illustrate the robustness of the
3 < matrix method to estimate the misidentification background correctly for varied
2 > The test described in the previous Section illustrates the robustness of the
3 > matrix method to estimate the background correctly for a different
4   jet flavor composition in the $\Z+jet$ sample.
5  
6   In the following we further scrutinize the details of the background estimation.
7 < We provide detailed information on the background extraction using the
8 < default selection criteria, that without the requirement on the \W candidate
9 < transverse mass, and finally using default selection criteria without subtracting
10 < backgrounds that have no genuine \Z bosons.
11 <
12 < \subsubsection{Details on extracting background with matrix method}
13 <
14 < In Fig.~\ref{fig:AllFits} we provide dilepton mass fit information for each channel
15 < for loose and tight \W lepton requirements using the full statistics of the CSA07 samples.
16 < The fit is performed using an addition of a convolution of a Gaussian and Breit-Wigner function
17 < and a line in order to fit the background. It has to be noticed that due to a lack
18 < of statistics in ``Chowder soup'' sample, all bins with 0 events from the sample
19 < have been modified in order to avoid to have a null uncertainty. The
20 < corresponding uncertainty in the bin with no events correspond to the weight
21 < of each process in the ``Chowder soup''. One can see that the uncertainties are
22 < large, and the fit is not really constrained.
7 > We test the performance of the matrix method on a sample selected with the
8 > full selection criteria but the requirement on the \W candidate transverse mass.
9 > We also test a possibility of extracting the background without categorization
10 > of the instrumental background contributions into genuine/fake \Z bosons.
11  
24 \begin{figure}[hbt]
25  \begin{center}
26  \scalebox{0.3}{\includegraphics{figs/Fit3eLoose.eps}\includegraphics{figs/Fit3eTight.eps}}\\
27  \scalebox{0.3}{\includegraphics{figs/Fit2e1muLoose.eps}\includegraphics{figs/Fit2e1muTight.eps}}\\
28  \scalebox{0.3}{\includegraphics{figs/Fit2mu1eLoose.eps}\includegraphics{figs/Fit2mu1eTight.eps}}\\
29  \scalebox{0.3}{\includegraphics{figs/Fit3muLoose.eps}\includegraphics{figs/Fit3muTight.eps}}\\
30  \caption{Invariant mass of \Z boson candidate for $3e$, $2e1\mu$, $2\mu1e$, and $3\mu$
31                  signatures (from top to bottom) for the lepton passing loose (left) and tight (right) identification
32                  criteria.}
33  \label{fig:AllFits}
34  \end{center}
35 \end{figure}
36
37 The linear fit takes into account not only the background with non-genuine
38 \Z boson but it also accounts for some part of the \Z+jets and
39 $Zb\bar{b}$ background as the $\gamma^*$ processes populate the sidebands as well.
40 However, the results are still consistent within errors, as it can be seen by comparison
41 of the last two columns in Table~\ref{tab:CompFit}.
42 \begin{table}[h]
43 \begin{center}
44 \begin{tabular}{|l|c|c|c|c|c|c|c|} \hline
45                    & \multicolumn{2}{c|}{Background with genuine \Z} & \multicolumn{4}{c|}{Background without
46                    genuine \Z boson} \\
47 Channel    & $\Z+jets$ & $\Z b\bar{b}$ &   $t\bar{t}$ & $\W+jets$ & Combined & Fit result \\ \hline
48 $3e$ Loose &7.1 & 2.9 & 1.1 & 0.4 & 1.5 & 1.5$ \pm $3.0 \\\hline
49 $3e$ Tight &2.0 & 1.2 & 0.6 & 0.4 & 1.0 & 1.1$ \pm $2.8 \\\hline
50 $2e1\mu$ Loose &4.0 & 4.7 & 6.2 & 0.0 & 6.2 & 6.0$ \pm $4.1 \\\hline
51 $2e1\mu$ Tight &0.0 & 0.1 & 0.7 & 0.0 & 0.7 & 1.0$ \pm $2.8 \\\hline  
52 $2\mu 1e$ Loose &10.1 & 2.9 & 0.8 & 0.0 & 0.8 & 1.6$ \pm $3.1 \\\hline
53 $2\mu 1e$ Tight &1.8 & 1.3 & 0.6 & 0.0 & 0.6 & 1.0$ \pm $2.7 \\\hline
54 $3\mu$ Loose &4.5 & 4.2 & 5.9 & 0.0 & 5.9 & 3.1$ \pm $3.5 \\\hline
55 $3\mu$ Tight &0.1 & 0.3 & 0.3 & 0.0 & 0.3 & 0.5$ \pm $2.5 \\\hline
56 \end{tabular}
57 \end{center}
58 \caption{Comparison between Monte Carlo truth information and the results of the fit for the background without genuine \Z boson. Number of events are obtained in the invariant mass range between 81 and 101 GeV. The ``Loose'' and ``Tight'' selection criteria applied on the \W lepton candidate.}
59 \label{tab:CompFit}
60 \end{table}
61
62 The comparison between estimated background and the MC truth information is provided
63 in Table~\ref{tab:FinalXCLoose} for ``Loose'' and \ref{tab:FinalXC} for ``Tight'' lepton candidates.
64 Within uncertainties the results agree with each other for every signature and every category of
65 \W lepton identification. The agreement between predicted and MC truth background
66 as function of the dilepton mass is given in Figs.~\ref{fig:FinalMatrix3e}-\ref{fig:FinalMatrix3mu}
67 for all four signal categories respectively.
68
69 \begin{table}[h]
70  \begin{center}
71 \begin{tabular}{lcccc} \hline \hline
72 & 3e &2e1$\mu$ &2$\mu$1e &3$\mu$\\ \hline
73 $N$ - \ZZ -\Z$\gamma$ &19.9$\pm$1.0&23.6$\pm$0.0&23.4$\pm$1.0&25.5$\pm$0.0\\ \hline
74 $N^{non genuine \Z}$ (Fit)&1.5$\pm$3.0&6.0$\pm$4.1&1.6$\pm$3.1&3.1$\pm$3.5\\ \hline
75 $N^{genuine \Z}$ (matrix method)&10.1 $\pm$6.8&15.8 $\pm$8.4&14.5 $\pm$6.8&15.8 $\pm$5.7\\ \hline
76 $N^{\WZ}$ & 8.8$\pm$7.5&7.8$\pm$11.1&7.9$\pm$7.6&9.8 $\pm$7.4\\ \hline
77 \WZ from MC &8.1&9.0& 9.2 &11.3\\
78 \hline
79 \end{tabular}
80 \caption{Expected number of selected events for an integrated luminosity of 300
81 pb$^{-1}$ for the signal and estimated background with 81 GeV $< M_Z < $ 101 GeV
82 with the full selection criteria applied but the requirement on the \W lepton which is
83 required to pass only ``Loose'' criteria.}
84 \label{tab:FinalXCLoose}
85 \end{center}
86 \end{table}
87
88 \begin{table}[h]
89  \begin{center}
90 \begin{tabular}{lcccc} \hline \hline
91 & 3e &2e1$\mu$ &2$\mu$1e &3$\mu$\\ \hline
92 $N$ - ZZ -Zgamma &12.4$\pm$1.0 &8.7$\pm$0.1 &13.1$\pm$0.9&10.6$\pm$0.0\\ \hline
93 $N^{non genuine Z}$ (Fit)&1.1$\pm$2.8&1.0$\pm$2.8&1.0$\pm$2.7&0.5$\pm$2.5\\ \hline
94 $N^{genuine Z}$ (matrix method)&3.2 $\pm$1.8&0.9 $\pm$1.1&4.6 $\pm$2.1&0.9 $\pm$1.1\\ \hline
95 $N^{WZ}$ & 8.2$\pm$3.5&7.7 $\pm$3.2 &7.6$\pm$3.5&9.6 $\pm$2.8\\ \hline
96 \WZ from MC &7.9&8.1& 9.0 &10.1\\ \hline
97 \end{tabular}
98 \caption{Expected number of selected events for an integrated luminosity of 300
99 pb$^{-1}$ for the signal and estimated background with 81 GeV $< M_Z < $ 101 GeV for
100 the full selection criteria applied.}
101 \label{tab:FinalXC}
102 \end{center}
103 \end{table}
104
105 \begin{figure}[hbt]
106  \begin{center}
107  \scalebox{0.62}{\includegraphics{figs/MatrixMethod3eLooseTightZmassMWtCut.eps}}
108  \caption{Comparison between background predicted with matrix method and MC truth information for the
109  $3e$ channel as a function of the \Z boson candidate invariant mass for loose (a, c) and tight (b, d) requirements
110  on the \W lepton for background (a, b) and signal (c, d).}
111  \label{fig:FinalMatrix3e}
112  \end{center}
113 \end{figure}
114
115 \begin{figure}[hbt]
116  \begin{center}
117  \scalebox{0.62}{\includegraphics{figs/MatrixMethod2e1muLooseTightZmassMWtCut.eps}}
118  \caption{
119  Comparison between background predicted with matrix method and MC truth information for the
120  $2e1\mu$ channel as a function of the \Z boson candidate invariant mass for loose (a, c) and tight (b, d) requirements
121  on the \W lepton for background (a, b) and signal (c, d).}
122    \label{fig:FinalMatrix2e1mu}
123  \end{center}
124 \end{figure}
125
126 \begin{figure}[hbt]
127  \begin{center}
128  \scalebox{0.62}{\includegraphics{figs/MatrixMethod2mu1eLooseTightZmassMWtCut.eps}}
129  \caption{Comparison between background predicted with matrix method and MC truth information for the
130  $2\mu 1e$ channel as a function of the \Z boson candidate invariant mass for loose (a, c) and tight (b, d) requirements
131  on the \W lepton for background (a, b) and signal (c, d).}
132  \label{fig:FinalMatrix2mu1e}
133  \end{center}
134 \end{figure}
135
136 \begin{figure}[hbt]
137  \begin{center}
138  \scalebox{0.62}{\includegraphics{figs/MatrixMethod3muLooseTightZmassMWtCut.eps}}
139  \caption{Comparison between background predicted with matrix method and MC truth information for the
140  $3\mu$ channel as a function of the \Z boson candidate invariant mass for loose (a, c) and tight (b, d) requirements
141  on the \W lepton for background (a, b) and signal (c, d).}
142  \label{fig:FinalMatrix3mu}
143  \end{center}
144 \end{figure}
145
146
147 \clearpage
12   \subsubsection{Background estimation without the \W boson transverse mass requirement}
13 + One of the ways to validate the matrix method is a comparison of its background
14 + prediction with the MC truth information at different stage of application of the
15 + \WZ signal selection criteria. We show that the matrix method works well with a very
16 + loose selection criteria (see the Section above). In the following we perform
17 + the comparison after applying the full selection criteria but the requirement on the
18 + \W candidate transverse mass.
19 +
20 + We repeat the procedure described in Section~\ref{sec:moreDetailsBackground} for
21 + every signature channels and provide the results of background estimation from processes
22 + without real \Z boson in Table~\ref{tab:FitNoMWt} and final results in
23 + Tables~\ref{tab:FinalNoMWtCutLoose} and \ref{tab:FinalNoMWtCut} for ``Loose''
24 + and ``Tight'' requirements on the \W lepton. The results agree with each other
25 + within one sigma of uncertainty.
26  
150 We also estimate background to the \WZ signal for the selection criteria without
151 the requirement on the transverse \W boson candidate mass. The results of
152 extraction of the background sources without real \Z boson are given in Table~\ref{tab:FitNoMWt}.
27   \begin{table}[h]
28   \begin{center}
29   \begin{tabular}{|l|c|c|c|c|c|c|c|} \hline
# Line 168 | Line 42 | $3mu$ Tight &0.8 & 2.3 & 0.3 & 0 & 0.3 &
42   \end{center}
43   \caption{Comparison between Monte Carlo truth information and the results of the fit for the background
44   without genuine \Z boson. Number of events are obtained in the invariant mass range between 81 and 101 GeV. The
45 < ``Loose'' and ``Tight'' selection criteria applied on the \W lepton.}
45 > ``Loose'' and ``Tight'' selection criteria applied on the \W lepton. No requirement is applied on the transverse
46 > \W candidate mass.}
47   \label{tab:FitNoMWt}
48   \end{table}
49  
175 The comparison between the estimated and MC truth backgrounds is given
176 in Tables~\ref{tab:FinalNoMWtCutLoose} and {tab:FinalNoMWtCut} for ``Loose''
177 and ``Tight'' requirements on the \W lepton. The results agree with each other
178 within one sigma of uncertainty.
179
50   \begin{table}[h]
51    \begin{center}
52   \begin{tabular}{lcccc} \hline \hline
53   & 3e &2e1$\mu$ &2$\mu$1e &3$\mu$\\ \hline
54 < $N$ - \ZZ -\Z$\gamma$  &75.3$\pm$7.3&146.6$\pm$0.0&90.4$\pm$5.9&156.9$\pm$0.0\\ \hline
55 < $N^{non genuine \Z}$ (Fit)&6.6$\pm$4.2&16.9$\pm$5.5&6.9$\pm$4.4&11.0$\pm$5.0\\ \hline
56 < $N^{genuine \Z}$ (matrix method)&58.5 $\pm$14.4&139.2 $\pm$20.3&73.2 $\pm$14.9& 147.7 $\pm$14.7\\ \hline
57 < $N^{\WZ}$  &9.5$\pm$16.4&7.4 $\pm$27.0&11.3 $\pm$17.0&  9.2 $\pm$19.0\\\hline
54 > $N$ - ZZ -Z$\gamma$                     &75.3$\pm$7.3     &146.6$\pm$0.1     & 90.4$\pm$5.9    & 156.9$\pm$0.1\\ \hline
55 > $N^{non genuine~Z}$ (Fit)             &6.6$\pm$4.2       &16.9$\pm$5.5       & 6.9$\pm$ 4.4      & 11.0$\pm$5.0\\ \hline
56 > $N^{genuine~Z}$ (matrix method)&52.5 $\pm$17.6 &122.2 $\pm$8.6   & 68.7 $\pm$15.1  & 136.0 $\pm$ 8.5\\ \hline
57 > $N^{\WZ}$                                          &16.3$\pm$19.5  &7.5 $\pm$10.2      &14.8 $\pm$16.8  &  10.0 $\pm$9.8\\\hline
58   \WZ from MC &12.0&14.2& 13.6 &17.2\\
59   \hline
60   \end{tabular}
61   \caption{Expected number of selected events for an integrated luminosity of 300 \invpb
62   for the signal and estimated background for 81 GeV $< M_Z < $ 101 GeV and for ``Loose''
63 < \W lepton.}
63 > \W lepton. No requirement is applied on the transverse \W candidate mass.}
64   \label{tab:FinalNoMWtCutLoose}
65   \end{center}
66   \end{table}
# Line 199 | Line 69 | $N^{\WZ}$  &9.5$\pm$16.4&7.4 $\pm$27.0&1
69    \begin{center}
70   \begin{tabular}{lcccc} \hline \hline
71   & 3e &2e1$\mu$ &2$\mu$1e &3$\mu$\\ \hline
72 < $N$ - \ZZ -\Z$\gamma$ &36.0$\pm$7.1&15.9$\pm$0.0&40.2$\pm$5.7&18.0$\pm$0.0\\ \hline
73 < $N^{non genuine \Z}$ (Fit)&3.8$\pm$3.5&1.5$\pm$3.2&4.1$\pm$2.5&0.8$\pm$2.8\\ \hline
74 < $N^{genuine \Z}$ (matrix method)&18.7 $\pm$6.1&8.4 $\pm$6.6&23.4 $\pm$7.5& 8.9 $\pm$7.1\\ \hline
75 < $N^{\WZ}$ &10.1 $\pm$8.0&7.6 $\pm$7.5&11.0 $\pm$8.9& 9.1 $\pm$7.6\\ \hline
72 > $N$ - ZZ -Z$\gamma$                     & 36.0 $\pm$7.1  & 15.2$\pm$0.1   & 40.2$\pm$5.7  & 18.0$\pm$0.1\\ \hline
73 > $N^{non genuine~Z}$ (Fit)               & 3.8  $\pm$3.5    & 1.5$\pm$3.2     & 4.1$\pm$2.5    & 0.8$\pm$2.8\\ \hline
74 > $N^{genuine~Z}$ (matrix method)  & 16.8 $\pm$6.1   &  7.3 $\pm$5.8  & 22.0 $\pm$7.4 & 8.2 $\pm$6.6\\ \hline
75 > $N^{\WZ}$                                            & 15.4 $\pm$10.0 &  7.1 $\pm$6.6 & 14.1 $\pm$9.7 & 9.1 $\pm$7.1\\ \hline
76   \WZ from MC &11.6&12.3& 13.3 &14.9\\
77   \hline
78   \end{tabular}
79 < \caption{Expected number of data events for an integrated luminosity of 300 \invpb for the signal and estimated background for 81 GeV $< M_Z < $ 101 GeV and for ``Tight'' \W lepton.}
79 > \caption{Expected number of data events for an integrated luminosity of 300 \invpb for the signal and estimated background for 81 GeV $< M_Z < $ 101 GeV and for ``Tight'' \W lepton. No requirement is applied
80 > on the transverse \W candidate mass.}
81   \label{tab:FinalNoMWtCut}
82   \end{center}
83   \end{table}
84  
85   \subsubsection{Performance of the matrix method without background categorization}
86 < The performance of the matrix method depends on the validity of the following two assumptions:
87 < the $p_{fake}$ should describe the probability of misidentified jets passing loose criteria to also
88 < pass tight lepton requirements, and there must be only one misidentified lepton. If the former
89 < challenge can be tackled by estimating $p_{fake}$ in the sample with the jet composition similar
90 < to that of the major \WZ background (\W+jets in this case), then the latter can be safely assumed
91 < if the sources of backgrounds with multiple leptons are suppressed. The latter can be checked
92 < with data by measuring comparing \W+jets cross-section measured in data with MC truth information
93 < and estimating the \W+jets background to the \WZ signal. As total $\W+jets$ background to
94 < \WZ signal is very small, we can neglect background contribution with multiple misidentified leptons
95 < to the signal.
96 <
97 < Therefore, with small data sample, it might be a good approximation not to divide instrumental
98 < background into genuine \Z boson and fake \Z boson categories, but apply the matrix method
99 < directly to the dilepton
100 < invariant mass after the physics backgrounds are subtracted. This results in smaller
101 < systematic uncertainties associated with the fit. We follow this procedure and provide the
102 < comparisons between predicted and true MC backgrounds
103 < in Tables~\ref{tab:FinalNoFitLoose} and \ref{tab:FinalNoFit} for ``Loose'' and ``Tight''
104 < \W lepton, respectively.
86 >
87 > The performance of the matrix method depends on the validity of the following three assumptions:
88 > \begin{itemize}
89 > \item the contribution from processes with two or more misidentified jets is negligible,
90 > \item $p_{fake}$ should describe the probability of misidentified jets passing loose criteria to also
91 > pass tight lepton requirements in the background to the signal,
92 > \item the misidentified lepton is associated with the \W candidate decay.
93 > \end{itemize}
94 >
95 > The first assumption is true for the \WZ analysis, and the second one is true if we assume
96 > that the jet composition in the control sample used to establish $p_{fake}$ is the same as that
97 > in the background in the \WZ data sample. This can be achieved by using $\W+X$
98 > processes as a control sample, as described in Section~\ref{sec:WPFake}. The latter assumption
99 > is generally not true for $t\bar{t}$ processes, and therefore, we subtract background
100 > without genuine \Z bosons using the fit results of the \Z candidate invariant mass.
101 >
102 > However, after applying the full selection criteria, the contribution from the backgrounds
103 > without real \Z boson is negligible, and the fit results in an unacceptable large uncertainty
104 > for the 300 \invpb scenario. Thus, it is possible to neglect the combinatorial bias from $t\bar{t}$
105 > processes with small integrated luminosity sample and forgo the fit altogether. In the following
106 > we provide the results of estimation of the background without subtracting the estimated
107 > non-genuine \Z boson background.
108 >
109 > The comparisons between predicted and true MC backgrounds are given in Tables~\ref{tab:FinalNoFitLoose}
110 > and \ref{tab:FinalNoFit} for ``Loose'' and ``Tight'' \W lepton, respectively.
111  
112   \begin{table}[h]
113    \begin{center}
114   \begin{tabular}{lcccc} \hline \hline
115 < & 3e &2e1$\mu$ &2$\mu$1e &3$\mu$\\ \hline
116 < $N$ - \ZZ -\Z$\gamma$  &19.9$\pm$1.0&23.6$\pm$0.0&23.4$\pm$1.0&25.5$\pm$0.0\\ \hline
117 < $N^{genuine \Z}$ (matrix method)&10.1 $\pm$0.6&0.9 $\pm$1.0&14.5 $\pm$0.9&15.8 $\pm$0.7\\ \hline
118 < $N^{\WZ}$  &8.8 $\pm$0.6&7.7 $\pm$1.0&7.9 $\pm$0.9&9.8 $\pm$0.7\\ \hline
115 >                                                        & 3e                       &2e1$\mu$          & 2$\mu$1e          &3$\mu$\\ \hline
116 > $N$ - ZZ - Z$\gamma$                       & 19.9$\pm$1.0   & 23.6$\pm$0.1  & 23.4$\pm$1.0   &  25.5$\pm$0.0\\ \hline
117 > $N^{genuine~Z}$ (matrix method)   & 10.0 $\pm$2.2  & 15.8 $\pm$0.7   & 14.5 $\pm$2.2  &  15.8 $\pm$0.7\\ \hline
118 > $N^{WZ}$                                              & 9.9 $\pm$2.4    &  7.8 $\pm$0.7  &   8.9 $\pm$2.4  &     9.8 $\pm$0.7\\ \hline
119   \WZ from MC &8.1&9.0& 9.2 &11.3\\
120   \hline
121   \end{tabular}
# Line 252 | Line 129 | and estimated background for 81 GeV $< M
129    \begin{center}
130   \begin{tabular}{lcccc} \hline \hline
131   & 3e &2e1$\mu$ &2$\mu$1e &3$\mu$\\ \hline
132 < $N$ - \ZZ -\Z$\gamma$ &12.4$\pm$1.0 &8.7$\pm$0&13.1$\pm$0.9&10.6$\pm$0.0\\ \hline
133 < $N^{genuine \Z}$ (matrix method)&3.2 $\pm$1.6&15.8 $\pm$0.7&4.6 $\pm$1.9&0.9 $\pm$1.1\\ \hline
134 < $N^{\WZ}$ &8.2 $\pm$1.6&7.8 $\pm$0.7&7.6 $\pm$1.9&9.6$\pm$1.1\\ \hline
132 > $N$ - ZZ -Z$\gamma$                     &12.4$\pm$1.0   &8.7$\pm$0.1            &13.1$\pm$0.9   &10.6$\pm$0.0\\ \hline
133 > $N^{genuine~Z}$ (matrix method) &3.2 $\pm$1.7           &0.9 $\pm$1.0   &4.6 $\pm$2.1   &0.9 $\pm$1.1\\ \hline
134 > $N^{\WZ}$                                       &9.2 $\pm$2.0           &7.7 $\pm$1.0           &8.5 $\pm$2.3   &9.6$\pm$1.1\\ \hline
135   \WZ from MC &7.9&8.1& 9.0 &10.1\\ \hline
136   \end{tabular}
137   \caption{Expected number of events for an integrated luminosity of 300 \invpb for the signal
# Line 262 | Line 139 | and estimated background for 81 GeV $< M
139   \label{tab:FinalNoFit}
140   \end{center}
141   \end{table}
142 < The agreement between estimated and MC true backgrounds is excellent.
142 > The agreement between estimated and MC true backgrounds is excellent. Smaller systematic uncertainty
143 > associated with the linear fit also results in a higher discovery potential, as described in the next Section.
144 >

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