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1   \section{Event reconstruction}
2   \label{sec:eventReconstruction}
3  
4 < The four possible final states of \WZ
5 < production with electrons and muons are studied, $\rm e^\pm \epem$, $\mu^\pm \epem$, $\rm e^\pm \mu^+\mu^-$
6 < and $\mu^\pm \mu^+\mu^-$. They are associated to four possible classes,
7 < denoted as follows:
4 > We categorize \WZ\ three-lepton final state as following
5   \begin{itemize}
6   \item $3e$: for \WZ events with $\W \to e \nu$ and $\Z\to \epem$.
7   \item $2e1\mu$: for \WZ events with $\W \to \mu \nu$ and $\Z\to \epem$.
# Line 19 | Line 16 | Events stemming from the three-lepton fi
16   are collected by the electron and/or muon triggers. For each channel,
17   a minimun number of HLT requirements is chosen while keeping
18   the HLT efficiency for selected events close to 100\%. The same
19 < HLT requirements are used for channels with the same Z decay mode:
19 > HLT requirements are used for channels with the same \Z decay mode:
20   \begin{itemize}
21   \item for $3e$ and $2e1\mu$: HLTSingleElectron or HLTDoubleElectronRelaxed
22   \item for $2\mu1e$ and $3\mu$: HLTSingleMuonIso
# Line 27 | Line 24 | HLT requirements are used for channels w
24   The HLT efficiencies for all modes for events passing the full
25   selection described in this section are given in table~\ref{tab:hlteff}.
26  
30
27   \begin{table}[tbph]
28   \begin{center}
29  
# Line 40 | Line 36 | $3\mu$     &   HLTSingleMuonIso
36   \end{tabular}
37  
38   \end{center}
39 < \caption{HLT Efficiencies, in percent, for all
40 <  the events in the generated phase space for events retained  by
45 <  the complete event selection.}
39 > \caption{HLT Efficiencies for all the events in the generated phase space that
40 >  have been retained  by the complete event selection.}
41   \label{tab:hlteff}
42   \end{table}
43  
44 +
45 + \begin{figure}[tbp]
46 +  \begin{center}
47 +  \scalebox{0.7}{\includegraphics{figs/mu_isol.eps}}
48 +  \caption{Muon isolation variables for the muon associated
49 +    to the \W boson decay in $2e1\mu$ events: in the left plot
50 +    we illustrate the sum of calorimetric energy in a $\Delta R=0.3$ cone
51 +    around the muon candidate; in the right plot we display the sum of
52 +    transverse momenta of tracks within a $\Delta R = 0.25$ cone around
53 +    the muon candidate. The normalization of signal and background
54 +    distributions is arbitrary.
55 + }
56 +  \label{fig:mu_isol}
57 +  \end{center}
58 + \end{figure}
59 +
60 + \begin{figure}[tb]
61 +  \begin{center}
62 +  \scalebox{0.6}{\includegraphics{figs/mu_SIP.eps}}
63 +  \caption{
64 +    Muon impact parameter significance distribution
65 +    in $2e1\mu$ events. The normalization of signal and background
66 +    distributions is arbitrary.
67 +  }
68 +  \label{fig:mu_SIP}
69 +  \end{center}
70 + \end{figure}
71 +
72 +
73   \subsection{Lepton identification}
74   \label{sec:leptonId}
75  
# Line 53 | Line 77 | The requirements used for electron ident
77   in~\cite{noteElectronID}.
78  
79   Muon candidates are selected from global muons, which are reconstructed
80 < combining measurements in the muon chambers and the central tracker.
81 < An additional isolation criterion requires that the energy
80 > by combining measurements in the muon chambers and the central tracker.
81 > An additional isolation criterion is imposed to require the energy
82   measured in the calorimeters within a $\Delta R = 0.3$ cone around the
83 < muon must be smaller than 3 GeV and the sum of the $p_t$ of tracks
84 < within a $\Delta R = 0.25$ cone around the muon must be smaller than 2
85 < GeV. These cuts reduce the background from muons originated in
83 > muon to be smaller than 3 GeV and the sum of the $p_T$ of tracks
84 > within a $\Delta R = 0.25$ cone around the muon must be smaller than 2 GeV.
85 > These cuts reduce the background from muons originated in
86   \b-quark decays of the $\Zbbbar$ background, which are close to tracks
87   and clusters from the other \b-quark decay products.
88 + The signal and background distributions of these isolation variables
89 + are shown in Figure~\ref{fig:mu_isol} for the muon in $2e1\mu$ candidate
90 + events.
91  
92   %Figures~\ref{fig:muonisol} and ~\ref{fig:muonisoleffi} show the
93   %performance of the isolation cut. The distribution of the isolation
# Line 69 | Line 96 | and clusters from the other \b-quark dec
96  
97   The significance of the muon impact parameter in the plane
98   transverse to the beam, $S_{IP}$, discriminates against leptons from
99 < heavy-quark decays in all Standard Model background processes. This
99 > heavy-quark decays in all standard model background processes. This
100   variable is defined as the ratio between the measured impact parameter
101   and its uncertainty: $S_{IP}=IP/\sigma_{IP}$, and is required to
102 < satisfy $S_{IP}<3$. This requirement is applied only for muons
103 < and not for electrons. For electrons, the dominant background
104 < comes from fake electrons and not from heavy quark decays.
102 > satisfy $S_{IP}<3$. This requirement is applied only for muon candidates
103 > and not for electrons. For electron candidates, a significant fraction of the
104 > background comes from misidentified light quark jets. Thus,
105 > the requirement on the impact parameter significance does not
106 > increase the significance of the $\W\to e$ channels, as can be seen in
107 > Fig.~\ref{fig:wl_IP_SvsCut}. The distribution of $S_{IP}$ for the muon
108 > in $2e1\mu$ candidate events is shown in Figure~\ref{fig:mu_SIP}.
109 >
110 > \begin{figure}[p]
111 >  \begin{center}
112 >  \scalebox{0.6}{\includegraphics{figs/wl_IP_eff.eps}}
113 >  \caption{Efficiency for signal and background as a function
114 >    of the requirement on the \W-boson lepton impact parameter
115 >    significance. All other criteria but the one on impact parameter
116 >    significance are applied.
117 > %    Only events with 81 GeV $< M_Z < $ 101 \gev
118 > %    are considered.
119 >  }
120 >  \label{fig:wl_IP_eff}
121 >  \end{center}
122 > %\end{figure}
123  
124 + %\begin{figure}[bt]
125 +  \begin{center}
126 +  \scalebox{0.6}{\includegraphics{figs/wl_IP_SvsCut.eps}}
127 +  \caption{Signal significance as a function of requirement on
128 +    the \W-boson lepton impact parameter significance. All other criteria but
129 +    the requirement on the impact parameter significance are applied.
130 + %    Only events with 81 GeV $< M_Z < $ 101 \gev are considered.
131 +  }
132 +  \label{fig:wl_IP_SvsCut}
133 +  \end{center}
134 + \end{figure}
135 +
136 +
137 + \begin{table}[tbp]
138 + \begin{tabular}{|l|c|c|c|c|} \hline
139 +              &  $3e$ & $2e1\mu$ & $2\mu 1e$ & $3\mu$ \\ \hline \hline
140 + \multicolumn{5}{|c|}{Lepton selection} \\ \hline
141 + Electrons     &   \multicolumn{3}{|c|}{{\tt SimpleLoose} requirements for \Z reconstruction} & \\
142 +              &   \multicolumn{3}{|c|}{{\tt SimpleTight} requirements for \W} &  \\ \hline
143 + Muons         &  &  \multicolumn{3}{|c|}{ Track Isolation:$ {\tt IsoTrack}(\Delta R= 0.25) < 2 \gev$}  \\
144 +              &  &  \multicolumn{3}{|c|}{ Calorimetric Isolation:$  {\tt IsoCalo}(\Delta R = 0.3)  < 5 \gev$}  \\
145 +              &  &  \multicolumn{3}{|c|}{$S_{IP}=IP/\sigma_{IP}<3$ }  \\ \hline
146 + HLT requirement & \multicolumn{2}{|c|}{ HLTSingleElectron or HLTDoubleElectronRelaxed}
147 +                & \multicolumn{2}{|c|}{  HLTSingleMuonIso} \\ \hline
148 + \multicolumn{5}{|c|}{\Z reconstruction} \\ \hline
149 + Lepton cuts   &  \multicolumn{4}{|c|}{for both \Z leptons: $p_T > 15$ GeV} \\
150 + Mass window   &  \multicolumn{4}{|c|}{$50 \gev < M_Z < 120 \gev $ } \\
151 + Second \Z veto &  \multicolumn{4}{|c|}{No independent second \Z candidate with $50 \gev < M_Z < 120 \gev $ } \\ \hline
152 + \multicolumn{5}{|c|}{\W lepton selection} \\ \hline
153 +
154 + Other cuts    &     &        & $\Delta R(\mu_Z,e_W)>0.1$ &  \\ \hline
155 + Signal region  &    \multicolumn{4}{|c|}{$81 \gev < M_Z < 101 \gev $ } \\ \hline \hline
156 +
157 + \end{tabular}
158 + \caption{Summary of the criteria we use to select \WZ\ final state}
159 + \label{tab:allcuts}
160 + \end{table}
161 +
162 +
163 + \begin{figure}[p]
164 +  \begin{center}
165 +  \scalebox{0.6}{\includegraphics{figs/wlpt_cuteff.eps}}
166 +  \caption{Efficiency for signal and background as a function
167 +    of the cut value on the \W-boson lepton transverse momentum.
168 +    All other cuts but the cut on this variable are applied.
169 +    Only events with 81 GeV $< M_Z < $ 101 \gev
170 +    are considered.}
171 +  \label{fig:wlpt_cuteff}
172 +  \end{center}
173 + %\end{figure}
174 +
175 + %\begin{figure}[bt]
176 +  \begin{center}
177 +  \scalebox{0.6}{\includegraphics{figs/wlpt_cutS.eps}}
178 +  \caption{Signal significance as a function of the cut value on
179 +    the \W-boson lepton transverse momentum. All other cuts but
180 +    the cut on this variable are applied. Only events with
181 +    81 GeV $< M_Z < $ 101 \gev are considered.}
182 +  \label{fig:wlpt_cutS}
183 +  \end{center}
184 + \end{figure}
185  
186  
187   \subsection{\WZ candidate selection}
188  
189   Events are accepted if they contain at least three charged leptons,
190 < either electrons or muons, with $p_t > 15\,\mathrm{GeV}$ and $| \eta | < 2.5$ for
191 < electrons,$| \eta | < 2.4$ for muons.
86 < as discussed in~\ref{sec:leptonId}.
190 > either electrons or muons, with $p_T > 15\,\mathrm{GeV}$ and $| \eta | < 2.5$ for
191 > electrons,$| \eta | < 2.4$ for muons, as discussed in Section~\ref{sec:leptonId}.
192  
193   The \WZ candidate selection proceeds from building all possible
194   \Z-boson candidates from same-flavour opposite-charge lepton pairs.
195 < For $\Z \to ee$ decays, electrons have to fullfil the loose requirements
195 > For $\Z \to ee$ decays, electron candidates have to fulfill the loose requirements
196   defined in~\cite{noteElectronID}.
197  
198 < Events are retained if the mass of this \Z-boson candidate is
199 < within 20 GeV of the Z-boson mass,$m_Z$. The event is
200 < rejected if a second Z candidate is found. This second Z candidate is done
201 < with all possible same-flavour opposite-charge combinations which are left
202 < after removing the two leptons already used for the first Z candidate. This
203 < veto on the presence of a second Z helps to suppress $ZZ$ events. The invariant
204 < mass distribution for accepted \Z candidates is shown in
205 < Figure~\ref{fig:zcandidates}.
198 > Events are retained if the mass of the \Z boson candidate is
199 > within 20 GeV of the \Z boson mass, $m_Z$. The event is
200 > rejected if a second \Z candidate is found. This second \Z boson candidate is formed
201 > using all possible same-flavour opposite-charge combinations which are left
202 > after removing the two leptons already used for the first \Z boson candidate. This
203 > secondary \Z boson veto helps to suppress $\Z\Z$ events.
204 > %The invariant
205 > %mass distribution for accepted \Z candidates is shown in
206 > %Figure~\ref{fig:zcandidates}.
207  
208   % and the \Z mass resolution is shown in
209   %Figure~\ref{fig:dzmass}.
210  
211 < After the \Z-boson candidate is identified, the lepton associated
212 < to the  \W-boson decay is chosen from the remaining electrons and muons
213 < in the event that have not been used for reconstructing the \Z-boson.
214 < Electrons are required to pass the tight criteria described in
215 < \cite{noteElectronID}.  If the event contains more than three leptons,
216 < the highest $p_t$ is chosen as the one from the \W-boson decay, and
217 < the additional leptons are not considered further.
218 < The transverse momentum of this lepton is required to be larger
219 < than 20 GeV. This last requirement is effective in rejecting
220 < the \Zbbbar and \Zjets backgrounds, and the cut value is chosen in
221 < the range that maximises the significance as shown in
222 < Figure~\ref{fig:s_vs_wlpt}.
223 <
224 < The expected number of events passing the various steps of the selection
225 < is listed in Tables~\ref{tab:sel-effA} and~\ref{tab:sel-effB}.
226 < Table~\ref{tab:wz-effimatrix} lists the final selection efficiency for
227 < the different generated \W and \Z decays. It can be seen there that \WZ\
228 < events with both the \W and the \Z boson decaying into electrons or muons
229 < almost always get reconstructed with the correct flavour. It is to be
230 < noted in addition that each of our four selection channels gets a small
231 < contribution from $W \to \tau \to e/\mu$ decays as one would expect. The
232 < selection efficiency for these events is however smaller which is mostly due
233 < to the \pt cut on the third lepton, since the \pt spectrum of electrons or
234 < muons from $W \to \tau \to e/\mu$ decays is softer.
211 > After the \Z boson candidate is identified, the remaining leptons in the event
212 > are required, for electrons, to pass the tight criteria described in~\cite{noteElectronID}
213 > or, for muons, all criteria described in section~\ref{sec:leptonId}.
214 > If more than one lepton candidate satisfies the tight requirements, the one with the
215 > highest $p_T$ is associated with \W boson decay. This lepton's $p_T$ is effective
216 > discriminant against \Zbbbar and \Zjets production (see Fig.~\ref{fig:wlpt_cuteff}).
217 > We require the transverse momentum to exceed 20 GeV, as it maximizes
218 > the significance of the \WZ\ signal with respect to background as shown in
219 > Fig.~\ref{fig:wlpt_cutS}.
220 >
221 > An additional requirement on the isolation between electron and muon candidates is applied
222 > for the $2\mu 1e$ channel, by demanding the value of $\Delta R$ between the electron
223 > candidate associated with the \W boson decay and any of the two muons associated with
224 > the \Z boson decay to be greater than 0.1.
225 >
226 > This requirement allows suppressing the contribution of $\Z \to \mu\mu$
227 > decays, where one of the two muons radiates a photon which is reconstructed
228 > as an electron, possibly after conversion. This can be seen as a peak in the dimuon
229 > invariant mass at  around 60 GeV in Fig.~\ref{fig:Z2mu1e_60GeVPeak}.
230 >
231 > The summary of the selection criteria is given in Table~\ref{tab:allcuts}.
232 >
233 > The expected number of the events satisfying the sequential steps of the selection
234 > is listed in Tables~\ref{tab:sel-effA}.  
235 > In Table~\ref{tab:wz-effimatrix} we list the total selection efficiency for  different
236 > \W and \Z boson decay modes. It can be seen lepton candidates from \W and \Z
237 > boson decays are almost always are reconstructed with the correct flavor. As expected,
238 > there is a small contribution from $\W \to \tau \nu_\tau \to \ell \nu_\ell \nu_\tau$
239 > decays. However, this contribution is suppressed, mostly due to $p_T$ requirement
240 > on the third lepton, as leptons from $\tau$ decays are not as energetic as those from
241 > $\W \to \ell \nu$ processes.
242 >
243 > In Tables~\ref{tab:wz-matcheffi-Zee} and \ref{tab:wz-matcheffi-Zmumu} we
244 > display the fraction of reconstructed \WZ events with correctly-matched leptons.
245 > It can be seen that the lepton associated with the \W boson decay is correctly matched
246 > to the true Monte Carlo lepton from the \W boson decay in more than 90\% of
247 > the cases, even for events with several lepton candidates available to be associated
248 > to the \W boson decay. The choice to take the lepton candidate with the leading $p_T$ is,
249 > therefore, justified.
250  
251   \begin{table}[p]
252    \begin{center}
253  
254 < \begin{tabular}{lcccc} \hline
255 < Step   & WZ  & Z+jets  & TTbar+jets  & bbll\\ \hline
256 < All events       & 546   & 1.2679e+06    & 17556.1       & 72770.4 \\
257 < Found $Z \to ee$         & 219.517 (40.2045 \%)  & 520695 (41.0674 \%)   & 3474.61 (19.7914 \%)  & 29563.3 (40.6254 \%) \\
258 < Z loose electron ID      & 219.517 (100 \%)      & 520695 (100 \%)       & 3474.61 (100 \%)      & 29563.3 (100 \%) \\
259 < Z Lepton Pt cut          & 216.371 (98.5671 \%)  & 515556 (99.0131 \%)   & 3289.22 (94.6645 \%)  & 29109.9 (98.4665 \%) \\
260 < Z Lepton $eta$ cut       & 216.371 (100 \%)      & 515556 (100 \%)       & 3289.22 (100 \%)      & 29109.9 (100 \%) \\
261 < Z Lepton IP cut          & 206.797 (95.5751 \%)  & 492205 (95.4707 \%)   & 3011.11 (91.5448 \%)  & 27833.5 (95.6153 \%) \\
262 < Found $W \to e$          & 42.8968 (20.7434 \%)  & 301.116 (0.061177 \%)         & 14.8797 (0.494158 \%)         & 173.054 (0.621745 \%) \\
263 < W Lepton $\eta$ cut      & 42.8968 (100 \%)      & 301.116 (100 \%)      & 14.8797 (100 \%)      & 173.054 (100 \%) \\
264 < W Lepton Pt cut          & 35.6425 (83.0889 \%)  & 86.9864 (28.8879 \%)  & 9.30549 (62.5383 \%)  & 23.9385 (13.833 \%) \\
265 < W tight electron ID      & 35.6425 (100 \%)      & 86.9864 (100 \%)      & 9.30549 (100 \%)      & 23.9385 (100 \%) \\
145 < Passes HLT               & 35.4852 (99.5587 \%)  & 85.9427 (98.8002 \%)  & 9.30549 (100 \%)      & 23.4938 (98.1424 \%) \\
146 < Z mass window    & 31.7106 (5.8078 \%)   & 54.1554 (0.00427126 \%)       & 3.2585 (0.0185605 \%)         & 17.046 (0.0234243\%) \\
254 > \begin{tabular}{lcc|cc|cc|cc|} \hline
255 > \multicolumn{9}{c}{ {\bf $3e$ Channel}} \\ \hline  \hline
256 > Step   & $\WZ \to 3e$ &  $ \epsilon$  & Z+jets &  $ \epsilon$  & TTbar+jets &  $ \epsilon$  & bbll &  $ \epsilon$\\ \hline
257 > All events       & 185 &         & $5.82\cdot 10^6$ &    & $8.27\cdot 10^5$ &    & $1.44\cdot 10^5$ &  \\
258 > Found $Z \to ee$         & 73.9 & 39.9 \%        & $5.02\cdot 10^5$ & 8.63 \%    & $2.92\cdot 10^3$ & 0.353 \%   & $2.78\cdot 10^4$ & 19.4 \% \\
259 > Second Z veto            & 73.9 & 100 \%         & $5.02\cdot 10^5$ & 100 \%     & $2.92\cdot 10^3$ & 99.9 \%    & $2.78\cdot 10^4$ & 100 \% \\
260 > Found $W \to e$          & 37.4 & 50.6 \%        & 310 & 0.0616 \%       & 13.8 & 0.474 \%       & 171 & 0.614 \% \\
261 > W Lepton Pt cut          & 32.5 & 86.7 \%        & 86.8 & 28 \%  & 8.26 & 59.7 \%        & 23.4 & 13.7 \% \\
262 > Passes HLT               & 32.3 & 99.6 \%        & 86.8 & 100 \%         & 8.26 & 100 \%         & 23.3 & 99.7 \% \\
263 > Z mass window    & 29.5 & 91.2 \%        & 51.9 & 59.8 \%        & 3.26 & 39.5 \%        & 17.3 & 74 \% \\
264 > \hline
265 >  Overall efficiency  &  &  15.9 \% &  &  0.000892 \% &  &  0.000394 \% &  &  0.012 \% \\
266   \hline
267 < \end{tabular}
268 <
269 <
270 < \begin{tabular}{lcccc} \hline
271 < Step   & WZ  & Z+jets  & TTbar+jets  & bbll\\ \hline
272 < All events       & 546   & 1.2679e+06    & 17556.1       & 72770.4 \\
273 < Found $Z \to ee$         & 219.517 (40.2045 \%)  & 520695 (41.0674 \%)   & 3474.61 (19.7914 \%)  & 29563.3 (40.6254 \%) \\
274 < Z electron ID loose      & 219.517 (100 \%)      & 520695 (100 \%)       & 3474.61 (100 \%)      & 29563.3 (100 \%) \\
275 < Z Lepton Pt cut          & 216.371 (98.5671 \%)  & 515556 (99.0131 \%)   & 3289.22 (94.6645 \%)  & 29109.9 (98.4665 \%) \\
276 < Z Lepton $eta$ cut       & 216.371 (100 \%)      & 515556 (100 \%)       & 3289.22 (100 \%)      & 29109.9 (100 \%) \\
277 < Z Lepton IP cut          & 206.797 (95.5751 \%)  & 492205 (95.4707 \%)   & 3011.11 (91.5448 \%)  & 27833.5 (95.6153 \%) \\
278 < Found $W \to \mu$        & 57.1892 (27.6547 \%)  & 5982.86 (1.21552 \%)  & 815.122 (27.0705 \%)  & 3808.22 (13.6821 \%) \\
279 < W Lepton $\eta$ cut      & 57.1695 (99.9656 \%)  & 5964.1 (99.6865 \%)   & 815.122 (100 \%)      & 3805.62 (99.9319 \%) \\
161 < W $\mu$ isolation        & 52.1367 (91.1967 \%)  & 2754.29 (46.1811 \%)  & 85.5097 (10.4904 \%)  & 1328.18 (34.9004 \%) \\
162 < W muon isolation         & 39.8889 (76.5083 \%)  & 22.2149 (0.806557 \%)         & 18.8521 (22.0468 \%)  & 16.6013 (1.24993 \%) \\
163 < Passes HLT               & 38.7683 (97.1907 \%)  & 21.2077 (95.466 \%)   & 16.5627 (87.8556 \%)  & 16.1566 (97.3214 \%) \\
164 < Z mass window    & 34.6399 (6.34429 \%)  & 17.3805 (0.00137081 \%)       & 5.4405 (0.0309891 \%)         & 14.0814 (0.0193505 \%) \\
267 > %\end{tabular}
268 > %\begin{tabular}{lcc|cc|cc|cc|} \hline
269 > \multicolumn{9}{c}{ {\bf $2e1\mu$ Channel}} \\ \hline  \hline
270 > Step   & $\WZ \to 2e1\mu$ &  $ \epsilon$  & Z+jets &  $ \epsilon$  & TTbar+jets &  $ \epsilon$  & bbll &  $ \epsilon$\\ \hline
271 > All events       & 185 &         & $5.82\cdot 10^6$ &    & $8.27\cdot 10^5$ &    & $1.44\cdot 10^5$ &  \\
272 > Found $Z \to ee$         & 63.8 & 34.5 \%        & $5.02\cdot 10^5$ & 8.63 \%    & $2.92\cdot 10^3$ & 0.353 \%   & $2.78\cdot 10^4$ & 19.4 \% \\
273 > Second Z veto            & 63.7 & 99.9 \%        & $5.02\cdot 10^5$ & 100 \%     & $2.92\cdot 10^3$ & 99.9 \%    & $2.78\cdot 10^4$ & 100 \% \\
274 > Found $W \to \mu$        & 42.6 & 66.8 \%        & $2.19\cdot 10^3$ & 0.437 \%   & 55.6 & 1.91 \%        & 748 & 2.69 \% \\
275 > W Lepton Pt cut          & 35.1 & 82.5 \%        & 9.58 & 0.436 \%       & 16.4 & 29.5 \%        & 9.49 & 1.27 \% \\
276 > Passes HLT               & 34.3 & 97.6 \%        & 8.32 & 86.9 \%        & 14.1 & 86 \%  & 9.12 & 96.1 \% \\
277 > Z mass window    & 30.8 & 89.8 \%        & 7.31 & 87.9 \%        & 3.76 & 26.7 \%        & 8 & 87.8 \% \\
278 > \hline
279 >  Overall efficiency  &  &  16.7 \% &  &  0.000126 \% &  &  0.000454 \% &  &  0.00557 \% \\
280   \hline
281 < \end{tabular}
282 <
283 < \begin{tabular}{lcccc} \hline
284 < Step   & WZ  & Z+jets  & TTbar+jets  & bbll\\ \hline
285 < All events       & 546   & 1.2679e+06    & 17556.1       & 72770.4 \\
286 < Found $Z \to \mu\mu$     & 326.484 (59.7955 \%)  & 748256 (59.0152 \%)   & 14081.6 (80.2087 \%)  & 43207.1 (59.3746 \%) \\
287 < Z muon isolation                 & 282.27 (86.4575 \%)   & 669556 (89.4822 \%)   & 4201.52 (29.837 \%)   & 37959.1 (87.8538 \%) \\
288 < Z Lepton $eta$ cut       & 282.27 (100 \%)       & 669547 (99.9987 \%)   & 4200.47 (99.975 \%)   & 37959.1 (99.9998 \%) \\
289 < Z Lepton Pt cut                  & 274.249 (97.1584 \%)  & 657267 (98.1659 \%)   & 3626.81 (86.3429 \%)  & 36945.8 (97.3306 \%) \\
290 < Z Lepton IP cut                  & 249.792 (91.0824 \%)  & 603257 (91.7827 \%)   & 3125.35 (86.1737 \%)  & 33937.7 (91.8581 \%) \\
291 < Found $W \to e$          & 51.9401 (20.7933 \%)  & 797.766 (0.132243 \%)         & 20.4415 (0.654055 \%)         & 228.342 (0.672826 \%) \\
292 < W Lepton $\eta$ cut      & 51.9401 (100 \%)      & 797.766 (100 \%)      & 20.4415 (100 \%)      & 228.342 (100 \%) \\
293 < W tight electron ID              & 51.9401 (100 \%)      & 797.766 (100 \%)      & 20.4415 (100 \%)      & 228.342 (100 \%) \\
294 < W Lepton Pt cut                  & 43.2703 (83.3081 \%)  & 519.647 (65.1378 \%)  & 15.0823 (73.7829 \%)  & 55.14 (24.148 \%)\\
180 < Passes HLT               & 41.8745 (96.7742 \%)  & 490.859 (94.46 \%)    & 13.533 (89.7275 \%)   & 54.2506 (98.3871 \%) \\
181 < Z mass window    & 37.5298 (6.87358 \%)  & 63.522 (0.00501 \%)   & 5.02282 (0.02861 \%)  & 20.0105 (0.0274981 \%) \\
281 > %\end{tabular}
282 > %\begin{tabular}{lcc|cc|cc|cc|} \hline
283 > \multicolumn{9}{c}{ {\bf $2\mu1e$ Channel}} \\ \hline  \hline
284 > Step   & $\WZ \to 2\mu1e$ &  $ \epsilon$  & Z+jets &  $ \epsilon$  & TTbar+jets &  $ \epsilon$  & bbll &  $ \epsilon$\\ \hline
285 > All events       & 190 &         & $5.82\cdot 10^6$ &    & $8.27\cdot 10^5$ &    & $1.44\cdot 10^5$ &  \\
286 > Found $Z \to \mu\mu$     & 75.2 & 39.7 \%        & $5.77\cdot 10^5$ & 9.92 \%    & $2.78\cdot 10^3$ & 0.336 \%   & $3.19\cdot 10^4$ & 22.2 \% \\
287 > Second Z veto            & 75.2 & 100 \%         & $5.77\cdot 10^5$ & 100 \%     & $2.77\cdot 10^3$ & 99.9 \%    & $3.19\cdot 10^4$ & 100 \% \\
288 > Found $W \to e$          & 44 & 58.5 \%  & 702 & 0.122 \%        & 15.1 & 0.544 \%       & 213 & 0.669 \% \\
289 > W Lepton Pt cut                  & 38.4 & 87.2 \%        & 464 & 66.2 \%         & 10.3 & 68 \%  & 50.5 & 23.7 \% \\
290 > $\Delta R(e,\mu)$ cut    & 38.4 & 99.9 \%        & 93 & 20 \%    & 7.15 & 69.6 \%        & 23.3 & 46 \% \\
291 > Passes HLT                       & 37.3 & 97.1 \%        & 88.8 & 95.5 \%        & 6.62 & 92.7 \%        & 23.1 & 99.4 \% \\
292 > Z mass window    & 33.6 & 90.1 \%        & 50.3 & 56.6 \%        & 2.84 & 42.9 \%        & 18.8 & 81.4 \% \\
293 > \hline
294 >  Overall efficiency  &  &  17.7 \% &  &  0.000864 \% &  &  0.000344 \% &  &  0.0131 \% \\
295   \hline
296 < \end{tabular}
297 <
298 < \begin{tabular}{lcccc} \hline
299 < Step   & WZ  & Z+jets  & TTbar+jets  & bbll\\ \hline
300 < All events       & 546   & 1.2679e+06    & 17556.1       & 72770.4 \\
301 < Found $Z \to \mu\mu$     & 326.484 (59.7955 \%)  & 748256 (59.0152 \%)   & 14081.6 (80.2087 \%)  & 43207.1 (59.3746 \%) \\
302 < Z muon isolation                 & 282.27 (86.4575 \%)   & 669556 (89.4822 \%)   & 4201.52 (29.837 \%)   & 37959.1 (87.8538 \%) \\
303 < Z Lepton $eta$ cut       & 282.27 (100 \%)       & 669547 (99.9987 \%)   & 4200.47 (99.975 \%)   & 37959.1 (99.9998 \%) \\
304 < Z Lepton Pt cut                  & 274.249 (97.1584 \%)  & 657267 (98.1659 \%)   & 3626.81 (86.3429 \%)  & 36945.8 (97.3306 \%) \\
305 < Z Lepton IP cut                  & 249.792 (91.0824 \%)  & 603257 (91.7827 \%)   & 3125.35 (86.1737 \%)  & 33937.7 (91.8581 \%) \\
306 < Found $W \to \mu$        & 73.015 (29.2303 \%)   & 7135.7 (1.18286 \%)   & 774.076 (24.7677 \%)  & 4435.51 (13.0696 \%) \\
307 < W Lepton $\eta$ cut      & 72.956 (99.9192 \%)   & 7110.07 (99.6409 \%)  & 774.076 (100 \%)      & 4432.32 (99.9282 \%) \\
308 < W $\mu$ isolation        & 66.724 (91.4578 \%)   & 3382.99 (47.5803 \%)  & 78.3017 (10.1155 \%)  & 1560.97 (35.2178 \%) \\
196 < W muon isolation         & 50.1118 (75.1031 \%)  & 6.25174 (0.184799 \%)         & 5.8096 (7.41951 \%)   & 20.6775 (1.32466 \%) \\
197 < Passes HLT               & 49.7972 (99.3723 \%)  & 6.25174 (100 \%)      & 5.8096 (100 \%)       & 20.6034 (99.6416 \%) \\
198 < Z mass window    & 45.1576 (8.27062 \%)  & 4.9976 (0.000394162 \%)       & 1.683 (0.00958638 \%)         & 18.3059 (0.0251557 \%) \\
296 > %\end{tabular}
297 > %\begin{tabular}{lcc|cc|cc|cc|} \hline
298 > \multicolumn{9}{c}{ {\bf $3\mu$ Channel}} \\ \hline  \hline
299 > Step   & $\WZ \to 3\mu$ &  $ \epsilon$  & Z+jets &  $ \epsilon$  & TTbar+jets &  $ \epsilon$  & bbll &  $ \epsilon$\\ \hline
300 > All events       & 189 &         & $5.82\cdot 10^6$ &    & $8.27\cdot 10^5$ &    & $1.44\cdot 10^5$ &  \\
301 > Found $Z \to \mu\mu$     & 83.8 & 44.3 \%        & $5.77\cdot 10^5$ & 9.92 \%    & $2.78\cdot 10^3$ & 0.336 \%   & $3.19\cdot 10^4$ & 22.2 \% \\
302 > Second Z veto            & 83.6 & 99.8 \%        & $5.77\cdot 10^5$ & 100 \%     & $2.77\cdot 10^3$ & 99.9 \%    & $3.19\cdot 10^4$ & 100 \% \\
303 > Found $W \to \mu$        & 51.8 & 62 \%  & $2.52\cdot 10^3$ & 0.437 \%   & 34.8 & 1.25 \%        & 810 & 2.54 \% \\
304 > W Lepton Pt cut                  & 42.5 & 81.9 \%        & 1.84 & 0.073 \%       & 1.16 & 3.33 \%        & 8.89 & 1.1 \% \\
305 > Passes HLT                       & 42.2 & 99.4 \%        & 1.84 & 100 \%         & 1.16 & 100 \%         & 8.89 & 100 \% \\
306 > Z mass window    & 38.5 & 91.1 \%        & 1.84 & 100 \%         & 1.16 & 100 \%         & 7.78 & 87.5 \% \\
307 > \hline
308 >  Overall efficiency  &  &  20.3 \% &  &  3.17e-05 \% &  &  0.00014 \% &  &  0.00542 \% \\
309   \hline
310   \end{tabular}
311 +
312   \caption{Expected number of signal and background events passing the different
313 <  selections steps in the \WZ, \ttbar and \Zbbbar samples for an integrated luminosity
313 >  selections steps together with the efficiency of each requirement and total efficiency of
314 >  selection criteria in the \WZ, \Zbbbar, \Zjets and \ttjets samples for an integrated luminosity
315    of 1 \invfb.}
316   \label{tab:sel-effA}
317   \end{center}
318   \end{table}
319  
320 + \begin{table}[p]
321 + \begin{center}
322 + \begin{tabular}{l|ccccc}
323 + \hline \hline
324 +   & \multicolumn{5}{c}{$\Z \to ee$ and \W decay modes below} \\
325 + Reconstruction channel  &  $e \nu$
326 +   &  $\mu \nu $
327 +   &  $\tau \nu \to e \nu \nu  $
328 +   &  $\tau \nu \to \mu \nu \nu $
329 +   &  $\tau \nu \to {\rm hadrons~} \nu$
330 + \\ \hline
331 + $3e$       &  17.4 \%  &  0.0319 \%  &  6.42 \%  &  0 \%  &  0.162 \% \\
332 + $2e1\mu$   &  0 \%  &  18.6 \%  &  0 \%  &  5.53 \%  &  0.0485 \% \\
333 + $2\mu1e$   &  0 \%  &  0 \%  &  0 \%  &  0 \%  &  0 \% \\
334 + $3\mu$     &  0 \%  &  0 \%  &  0 \%  &  0 \%  &  0 \% \\
335 + \hline \hline
336 +
337 + & \multicolumn{5}{c}{$\Z \to \mu\mu$ and \W decay modes below} \\
338 + Reconstruction channel  &  $e\nu$
339 +   &  $\mu\nu$
340 +   &  $\tau\nu \to e\nu\nu$
341 +   &  $\tau\nu \to \mu\nu\nu$
342 +   &  $\tau\nu \to {\rm hadrons~}\nu$
343 + \\ \hline
344 + $3e$        &  0 \%  &  0 \%  &  0 \%  &  0 \%  &  0 \% \\
345 + $2e1\mu$   &  0.0104 \%  &  0 \%  &  0 \%  &  0 \%  &  0 \% \\
346 + $2\mu1e$   &  19.6 \%  &  0.0208 \%  &  5.56 \%  &  0 \%  &  0.18 \% \\
347 + $3\mu$     &  0 \%  &  23.4 \%  &  0.0573 \%  &  6.77 \%  &  0.0164 \% \\
348 + \hline \hline
349 + \end{tabular}
350 + \end{center}
351 + \caption{Selection efficiency for signal events in the four selection channels for the different
352 +  generated \W and \Z decay channels.}
353 + \label{tab:wz-effimatrix}
354  
355 + %\end{table}
356 + %\begin{table}[tbp]
357 + \begin{center}
358 + \begin{tabular}{llcc} \hline
359 +  & & \multicolumn{2}{c}{Generated decay} \\
360 +  & & \multicolumn{2}{c}{$\Z \to ee $} \\
361 + Selection channel  &    &  $\W \to e\nu$   &  $\W \to \mu\nu$ \\
362 + \hline \hline
363 + \multicolumn{4}{c}{all} \\ \hline
364 + $3e$        & all & 1644 events         & 3 events    \\
365 + $3e$        & matched \Z & 93$\pm$1\% & 100\%\\
366 + $3e$        & matched \W & 92$\pm$1\% & 0\\
367 + $3e$        & matched \WZ & 91$\pm$1\% & 0\\
368 + \hline \hline
369 +
370 + \multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline
371 + $3e$        & all & 1602  events       & 0 events    \\
372 + $3e$        & matched \Z & 94$\pm$1\% & 0\\
373 + $3e$        & matched \W & 92$\pm$1\% & 0\\
374 + $3e$        & matched \WZ & 91$\pm$1\% & 0\\
375 + \hline \hline
376 +
377 + \multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline
378 + $3e$        & all & 42 events  & 3 events   \\
379 + $3e$        & matched \Z & 93$\pm$4\% & 100\%\\
380 + $3e$        & matched \W & 91 $\pm$5\% & 0\\
381 + $3e$        & matched \WZ & 91$\pm$5\% & 0\\
382 + \hline \hline
383 +
384 + \multicolumn{4}{c}{all} \\ \hline
385 + $2e1\mu$   & all & 0  events   & 1746 events \\
386 + $2e1\mu$   & matched \Z & 0 & 100\%\\
387 + $2e1\mu$   & matched \W & 0 & 100\%\\
388 + $2e1\mu$   & matched \WZ & 0 & 100\%\\
389 + \hline \hline
390 +
391 + \multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline
392 + $2e1\mu$   & all & 0 events    & 1715 events \\
393 + $2e1\mu$   & matched \Z & 0 & 100\%\\
394 + $2e1\mu$   & matched \W & 0 & 100\%\\
395 + $2e1\mu$   & matched \WZ & 0 & 100\%\\
396 + \hline \hline
397 +
398 + \multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline
399 + $2e1\mu$   & all & 0     & 31   \\
400 + $2e1\mu$   & matched \Z & 0 & 100\%\\
401 + $2e1\mu$   & matched \W & 0 & 100\%\\
402 + $2e1\mu$   & matched \WZ & 0 & 100\% \\ \hline \hline
403 + \end{tabular}
404 + \end{center}
405 + \caption{Fractions of events with correctly matched leptons
406 +  to true decay product of \W and \Z decays for final states
407 +  with generated $\Z\to ee$ decays}
408 + \label{tab:wz-matcheffi-Zee}
409 + \end{table}
410  
210 \subsection{Signal extraction}
211 \input D0Matrix
411  
412  
413 < \subsection{Systematic uncertainties}
413 > \begin{table}[tbp]
414 > \begin{center}
415 > \begin{tabular}{llcc} \hline
416 >  & & \multicolumn{2}{c}{Generated decay:} \\
417 > & & \multicolumn{2}{c}{$\Z \to \mu\mu $} \\
418 > Selection channel  &    &  $\W \to e\nu$   &  $\W \to \mu\nu$
419 > \\
420 > \hline \hline
421 > \multicolumn{4}{c}{all} \\ \hline
422 > $2\mu1e$   & all & 1895 events  & 2 events   \\
423 > $2\mu1e$   & matched \Z & 100\% & 100\%\\
424 > $2\mu1e$   & matched \W & 99$\pm$1\% & 0\\
425 > $2\mu1e$   & matched \WZ & 99$\pm$1\% & 0\\
426 > \hline \hline
427 >
428 > \multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline
429 > $2\mu1e$   & all & 1847 events & 0 events    \\
430 > $2\mu1e$   & matched \Z & 100\% & 0\\
431 > $2\mu1e$   & matched \W & 99$\pm$1\% & 0\\
432 > $2\mu1e$   & matched \WZ & 99$\pm$1\% & 0\\
433 > \hline \hline
434 >
435 > \multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline
436 > $2\mu1e$   & all & 48 events   & 2 events    \\
437 > $2\mu1e$   & matched \Z & 100\% & 100\%\\
438 > $2\mu1e$   & matched \W & 94$\pm$3.5\%& 0\\
439 > $2\mu1e$   & matched \WZ & 94$\pm$3.5\% & 0\\
440 > \hline \hline
441 >
442 > \multicolumn{4}{c}{all} \\ \hline
443 > $3\mu$     & all & 0 events   & 2251 events \\
444 > $3\mu$     & matched \Z & 0 & 94$\pm$1\%\\
445 > $3\mu$     & matched \W & 0 & 93$\pm$1\%\\
446 > $3\mu$     & matched \WZ & 0 & 93$\pm$1\%\\
447 > \hline \hline
448 >
449 > \multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline
450 > $3\mu$     & all & 0 events    & 2207 events \\
451 > $3\mu$     & matched \Z & 0 & 94$\pm$1\%\\
452 > $3\mu$     & matched \W & 0 & 93$\pm$1\%\\
453 > $3\mu$     & matched \WZ & 0 & 93$\pm$1\%\\
454 > \hline \hline
455 >
456 > \multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline
457 > $3\mu$     & all & 0 events    & 44 events  \\
458 > $3\mu$     & matched \Z & 0 & 91$\pm$4\%\\
459 > $3\mu$     & matched \W & 0 & 91$\pm$4\%\\
460 > $3\mu$     & matched \WZ & 0 & 91$\pm$4\%\\ \hline \hline
461 > \end{tabular}
462 > \end{center}
463 > \caption{Fractions of MC \WZ events with correctly matched leptons
464 >  to true decay product of \W and \Z decays for final states
465 >  with generated $\Z\to \mu\mu$ decays}
466 > \label{tab:wz-matcheffi-Zmumu}
467 > \end{table}
468 >
469 >
470 > %\subsection{Signal extraction}
471 > %\input D0Matrix
472 > \input zjetbackground
473 >
474 >
475 > \subsection{Complementary studies: can we use the neutrino?}
476 >
477 > In $\WZ \to  \ell^{\pm}\nu \ellell (\ell=e,\mu)$ events, the neutrino
478 > coming from the \W-boson decay leaves the detector with a significant
479 > amount of energy, which should reflect in a large transverse missing
480 > energy measurement. On the other side, no large MET is expected for
481 > the  most  important background categories, especially \Zjets,
482 > \Zbbbar, \ZZ and \Zgamma. This expectation is confirmed, as can be
483 > seen in Figure~\ref{fig:met}.
484 >
485 > Another variable sensitive to the presence of the neutrino
486 > is the W transverse mass $m_T^W$, obtained by combining the missing
487 > energy vector and the lepton associated to the \W-boson decay.
488 > The distribution of $m_T^W$ is shown in Figure~\ref{fig:mtw}.
489 > The signal yield could be extracted from that distribution.
490 > This requires however additional studies and it has not been
491 > done at this stage.
492 >
493 >
494 > \section{Systematic uncertainties}
495   \input Sys
496  
497  
498   \begin{figure}[bt]
499    \begin{center}
500 +  \scalebox{0.8}{\includegraphics{figs/met_by_channel.eps}}
501 +  \caption{Missing transverse energy for the four signal categories.
502 +    The distributions  show the number of expected events
503 +    for $1 fb^{-1}$. Only events with 81 GeV $< M_Z < $ 101 \gev
504 +    are shown. All selection cuts are applied.}
505 +  \label{fig:met}
506 +  \end{center}
507 + \end{figure}
508 +
509 + \begin{figure}[bt]
510 +  \begin{center}
511    \scalebox{0.8}{\includegraphics{figs/mtw_by_channel.eps}}
512 <  \caption{W transverse mass for the four signal categories.
512 >  \caption{\W transverse mass for the four signal categories.
513      The distributions  show the number of expected events
514 <    for $1 fb^{-1}$. Only events with 81.1 GeV $< M_Z < $ 101.1 GeV are shown.}
514 >    for $1 fb^{-1}$. Only events with 81 GeV $< M_Z < $ 101 GeV are shown.
515 >    All selection cuts are applied.}
516    \label{fig:mtw}
517    \end{center}
518   \end{figure}
519 +
520 +
521 +
522 +
523 +

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