| 1 |
\section{Event reconstruction}
|
| 2 |
\label{sec:eventReconstruction}
|
| 3 |
|
| 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 $\Z\to \epem$.
|
| 8 |
\item $2\mu 1e$: for \WZ events with $\W \to e \nu$ and $\Z\to \mumu$.
|
| 9 |
\item $3\mu$: for \WZ events with $\W \to \mu \nu$ and $\Z\to \mumu$.
|
| 10 |
\end{itemize}
|
| 11 |
|
| 12 |
|
| 13 |
\subsection{Trigger selection and efficiencies}
|
| 14 |
|
| 15 |
Events stemming from the three-lepton final states of $\WZ$ production
|
| 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:
|
| 20 |
\begin{itemize}
|
| 21 |
\item for $3e$ and $2e1\mu$: HLTSingleElectron or HLTDoubleElectronRelaxed
|
| 22 |
\item for $2\mu1e$ and $3\mu$: HLTSingleMuonIso
|
| 23 |
\end{itemize}
|
| 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 |
|
| 27 |
\begin{table}[tbph]
|
| 28 |
\begin{center}
|
| 29 |
|
| 30 |
\begin{tabular}{llc} \hline \hline
|
| 31 |
Channel & HLT selection & HLT efficiency \\ \hline
|
| 32 |
$3e$ & HLTSingleElectron or HLTDoubleElectronRelaxed & 0.996 \\
|
| 33 |
$2e1\mu$ & HLTSingleElectron or HLTDoubleElectronRelaxed & 0.969 \\
|
| 34 |
$2\mu 1e$ & HLTSingleMuonIso & 0.966 \\
|
| 35 |
$3\mu$ & HLTSingleMuonIso & 0.994 \\ \hline \hline
|
| 36 |
\end{tabular}
|
| 37 |
|
| 38 |
\end{center}
|
| 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 |
|
| 76 |
The requirements used for electron identification in this analysis are described
|
| 77 |
in~\cite{noteElectronID}.
|
| 78 |
|
| 79 |
Muon candidates are selected from global muons, which are reconstructed
|
| 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 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
|
| 94 |
%variables for the $\Z\b\bbar(\epem\b\bbar)$ is particularly
|
| 95 |
%interesting, since muons only stem from \b-quark decays.
|
| 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
|
| 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 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 |
The muons fullfilling all these requirements will be called ``tight'', while global
|
| 111 |
muons without requirements on isolation or impact parameter significance are called ``loose''.
|
| 112 |
|
| 113 |
\begin{figure}[p]
|
| 114 |
\begin{center}
|
| 115 |
\scalebox{0.6}{\includegraphics{figs/wl_IP_eff.eps}}
|
| 116 |
\caption{Efficiency for signal and background as a function
|
| 117 |
of the requirement on the \W-boson lepton impact parameter
|
| 118 |
significance. All other criteria but the one on impact parameter
|
| 119 |
significance are applied.
|
| 120 |
% Only events with 81 GeV $< M_Z < $ 101 \gev
|
| 121 |
% are considered.
|
| 122 |
}
|
| 123 |
\label{fig:wl_IP_eff}
|
| 124 |
\end{center}
|
| 125 |
%\end{figure}
|
| 126 |
|
| 127 |
%\begin{figure}[bt]
|
| 128 |
\begin{center}
|
| 129 |
\scalebox{0.6}{\includegraphics{figs/wl_IP_SvsCut.eps}}
|
| 130 |
\caption{Signal significance as a function of requirement on
|
| 131 |
the \W-boson lepton impact parameter significance. All other criteria but
|
| 132 |
the requirement on the impact parameter significance are applied.
|
| 133 |
% Only events with 81 GeV $< M_Z < $ 101 \gev are considered.
|
| 134 |
}
|
| 135 |
\label{fig:wl_IP_SvsCut}
|
| 136 |
\end{center}
|
| 137 |
\end{figure}
|
| 138 |
|
| 139 |
|
| 140 |
\begin{table}[tbp]
|
| 141 |
\begin{tabular}{|l|c|c|c|c|} \hline
|
| 142 |
& $3e$ & $2e1\mu$ & $2\mu 1e$ & $3\mu$ \\ \hline \hline
|
| 143 |
\multicolumn{5}{|c|}{Lepton selection} \\ \hline
|
| 144 |
Electrons & \multicolumn{3}{|c|}{{\tt SimpleLoose} requirements for \Z reconstruction} & \\
|
| 145 |
& \multicolumn{3}{|c|}{{\tt SimpleTight} requirements for \W} & \\ \hline
|
| 146 |
Muons & & \multicolumn{3}{|c|}{ Track Isolation:$ {\tt IsoTrack}(\Delta R= 0.25) < 2 \gev$} \\
|
| 147 |
& & \multicolumn{3}{|c|}{ Calorimetric Isolation:$ {\tt IsoCalo}(\Delta R = 0.3) < 5 \gev$} \\
|
| 148 |
& & \multicolumn{3}{|c|}{$S_{IP}=IP/\sigma_{IP}<3$ } \\ \hline
|
| 149 |
HLT requirement & \multicolumn{2}{|c|}{ HLTSingleElectron or HLTDoubleElectronRelaxed}
|
| 150 |
& \multicolumn{2}{|c|}{ HLTSingleMuonIso} \\ \hline
|
| 151 |
\multicolumn{5}{|c|}{\Z reconstruction} \\ \hline
|
| 152 |
Lepton cuts & \multicolumn{4}{|c|}{for both \Z leptons: $p_T > 15$ GeV} \\
|
| 153 |
Mass window & \multicolumn{4}{|c|}{$50 \gev < M_Z < 120 \gev $ } \\
|
| 154 |
Second \Z veto & \multicolumn{4}{|c|}{No independent second \Z candidate with $50 \gev < M_Z < 120 \gev $ } \\ \hline
|
| 155 |
\multicolumn{5}{|c|}{\W lepton selection} \\ \hline
|
| 156 |
|
| 157 |
Other cuts & & & $\Delta R(\mu_Z,e_W)>0.1$ & \\ \hline
|
| 158 |
Signal region & \multicolumn{4}{|c|}{$81 \gev < M_Z < 101 \gev $ } \\ \hline \hline
|
| 159 |
|
| 160 |
\end{tabular}
|
| 161 |
\caption{Summary of the criteria we use to select \WZ\ final state}
|
| 162 |
\label{tab:allcuts}
|
| 163 |
\end{table}
|
| 164 |
|
| 165 |
|
| 166 |
\begin{figure}[p]
|
| 167 |
\begin{center}
|
| 168 |
\scalebox{0.6}{\includegraphics{figs/wlpt_cuteff.eps}}
|
| 169 |
\caption{Efficiency for signal and background as a function
|
| 170 |
of the cut value on the \W-boson lepton transverse momentum.
|
| 171 |
All other cuts but the cut on this variable are applied.
|
| 172 |
Only events with 81 GeV $< M_Z < $ 101 \gev
|
| 173 |
are considered.}
|
| 174 |
\label{fig:wlpt_cuteff}
|
| 175 |
\end{center}
|
| 176 |
%\end{figure}
|
| 177 |
|
| 178 |
%\begin{figure}[bt]
|
| 179 |
\begin{center}
|
| 180 |
\scalebox{0.6}{\includegraphics{figs/wlpt_cutS.eps}}
|
| 181 |
\caption{Signal significance as a function of the cut value on
|
| 182 |
the \W-boson lepton transverse momentum. All other cuts but
|
| 183 |
the cut on this variable are applied. Only events with
|
| 184 |
81 GeV $< M_Z < $ 101 \gev are considered.}
|
| 185 |
\label{fig:wlpt_cutS}
|
| 186 |
\end{center}
|
| 187 |
\end{figure}
|
| 188 |
|
| 189 |
|
| 190 |
\subsection{\WZ candidate selection}
|
| 191 |
|
| 192 |
Events are accepted if they contain at least three charged leptons,
|
| 193 |
either electrons or muons, with $p_T > 15\,\mathrm{GeV}$ and $| \eta | < 2.5$ for
|
| 194 |
electrons,$| \eta | < 2.4$ for muons, as discussed in Section~\ref{sec:leptonId}.
|
| 195 |
|
| 196 |
The \WZ candidate selection proceeds from building all possible
|
| 197 |
\Z-boson candidates from same-flavour opposite-charge lepton pairs.
|
| 198 |
For $\Z \to ee$ decays, electron candidates have to fulfill the loose requirements
|
| 199 |
defined in~\cite{noteElectronID}.
|
| 200 |
|
| 201 |
Events are retained if the mass of the \Z boson candidate is
|
| 202 |
within 20 GeV of the \Z boson mass, $m_Z$. The event is
|
| 203 |
rejected if a second \Z candidate is found. This second \Z boson candidate is formed
|
| 204 |
using all possible same-flavour opposite-charge combinations which are left
|
| 205 |
after removing the two leptons already used for the first \Z boson candidate. This
|
| 206 |
secondary \Z boson veto helps to suppress $\Z\Z$ events.
|
| 207 |
%The invariant
|
| 208 |
%mass distribution for accepted \Z candidates is shown in
|
| 209 |
%Figure~\ref{fig:zcandidates}.
|
| 210 |
|
| 211 |
% and the \Z mass resolution is shown in
|
| 212 |
%Figure~\ref{fig:dzmass}.
|
| 213 |
|
| 214 |
After the \Z boson candidate is identified, the remaining leptons in the event
|
| 215 |
are required, for electrons, to pass the tight criteria described in~\cite{noteElectronID}
|
| 216 |
or, for muons, all criteria described in section~\ref{sec:leptonId}.
|
| 217 |
If more than one lepton candidate satisfies the tight requirements, the one with the
|
| 218 |
highest $p_T$ is associated with \W boson decay. This lepton's $p_T$ is effective
|
| 219 |
discriminant against \Zbbbar and \Zjets production (see Fig.~\ref{fig:wlpt_cuteff}).
|
| 220 |
We require the transverse momentum to exceed 20 GeV, as it maximizes
|
| 221 |
the significance of the \WZ\ signal with respect to background as shown in
|
| 222 |
Fig.~\ref{fig:wlpt_cutS}.
|
| 223 |
|
| 224 |
An additional requirement on the isolation between electron and muon candidates is applied
|
| 225 |
for the $2\mu 1e$ channel, by demanding the value of $\Delta R$ between the electron
|
| 226 |
candidate associated with the \W boson decay and any of the two muons associated with
|
| 227 |
the \Z boson decay to be greater than 0.1.
|
| 228 |
|
| 229 |
This requirement allows suppressing the contribution of $\Z \to \mu\mu$
|
| 230 |
decays, where one of the two muons radiates a photon which is reconstructed
|
| 231 |
as an electron, possibly after conversion.
|
| 232 |
% ADD THE PLOT TO JUSTIFY THIS COMMENT
|
| 233 |
% This can be seen as a peak in the dimuon
|
| 234 |
%invariant mass at around 60 GeV in Fig.~\ref{fig:Z2mu1e_60GeVPeak}.
|
| 235 |
|
| 236 |
The summary of the selection criteria is given in Table~\ref{tab:allcuts}.
|
| 237 |
|
| 238 |
The expected number of the events satisfying the sequential steps of the selection
|
| 239 |
is listed in Tables~\ref{tab:sel-effA} and~\ref{tab:sel-effB}.
|
| 240 |
In Table~\ref{tab:wz-effimatrix} we list the total selection efficiency for different
|
| 241 |
\W and \Z boson decay modes. It can be seen lepton candidates from \W and \Z
|
| 242 |
boson decays are almost always are reconstructed with the correct flavor. As expected,
|
| 243 |
there is a small contribution from $\W \to \tau \nu_\tau \to \ell \nu_\ell \nu_\tau$
|
| 244 |
decays. However, this contribution is suppressed, mostly due to $p_T$ requirement
|
| 245 |
on the third lepton, as leptons from $\tau$ decays are not as energetic as those from
|
| 246 |
$\W \to \ell \nu$ processes.
|
| 247 |
|
| 248 |
In Tables~\ref{tab:wz-matcheffi-Zee} and \ref{tab:wz-matcheffi-Zmumu} we
|
| 249 |
display the fraction of reconstructed \WZ events with correctly-matched leptons.
|
| 250 |
It can be seen that the lepton associated with the \W boson decay is correctly matched
|
| 251 |
to the true Monte Carlo lepton from the \W boson decay in more than 90\% of
|
| 252 |
the cases, even for events with several lepton candidates available to be associated
|
| 253 |
to the \W boson decay. The choice to take the lepton candidate with the leading $p_T$ is,
|
| 254 |
therefore, justified.
|
| 255 |
|
| 256 |
\begin{table}[p]
|
| 257 |
\begin{center}
|
| 258 |
|
| 259 |
\begin{tabular}{lcc|cc|cc|cc|} \hline
|
| 260 |
\multicolumn{9}{c}{ {\bf $3e$ Channel}} \\ \hline \hline
|
| 261 |
Step & $\WZ \to 3e\nu$ & $ \epsilon$ & $\Z+jets$ & $ \epsilon$ & $t\bar{t}+jets$ & $ \epsilon$ & $b\bar{b}\ell\ell$ & $ \epsilon$\\ \hline
|
| 262 |
All events & 185 & & $5.82\cdot 10^6$ & & $8.27\cdot 10^5$ & & $1.44\cdot 10^5$ & \\
|
| 263 |
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\% \\
|
| 264 |
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\% \\
|
| 265 |
Found $\W \to e\nu$ & 37.4 & 50.6\% & 310 & 0.062\% & 13.8 & 0.474\% & 171 & 0.61\% \\
|
| 266 |
\W lepton $p_T$ cut & 32.5 & 86.7\% & 86.8 & 28\% & 8.26 & 59.7\% & 23.4 & 13.7\% \\
|
| 267 |
Passes HLT & 32.3 & 99.6\% & 86.8 & 100\% & 8.26 & 100\% & 23.3 & 99.7\% \\
|
| 268 |
\Z mass window & 29.5 & 91.2\% & 51.9 & 59.8\% & 3.26 & 39.5\% & 17.3 & 74\% \\
|
| 269 |
\hline
|
| 270 |
Overall efficiency & & 15.9\% & & 0.00089\% & & 0.00039\% & & 0.012\% \\
|
| 271 |
\hline
|
| 272 |
|
| 273 |
\multicolumn{9}{c}{ {\bf $2e1\mu$ Channel}} \\ \hline \hline
|
| 274 |
Step & $\WZ \to 2e1\mu\nu$ & $ \epsilon$ & $\Z+jets$ & $ \epsilon$ & $t\bar{t}+jets$ & $ \epsilon$ & $b\bar{t}\ell\ell$ & $ \epsilon$\\ \hline
|
| 275 |
All events & 185 & & $5.82\cdot 10^6$ & & $8.27\cdot 10^5$ & & $1.44\cdot 10^5$ & \\
|
| 276 |
Found $\Z \to ee$ & 63.8 & 34.5\% & $5.02\cdot 10^5$ & 8.63\% & $2.92\cdot 10^3$ & 0.35\% & $2.78\cdot 10^4$ & 19.4\% \\
|
| 277 |
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\% \\
|
| 278 |
Found $\W \to \mu\nu$ & 42.6 & 66.8\% & $2.19\cdot 10^3$ & 0.44\% & 55.6 & 1.91\% & 748 & 2.69\% \\
|
| 279 |
\W lepton $p_T$ cut & 35.1 & 82.5\% & 9.58 & 0.44\% & 16.4 & 29.5\% & 9.49 & 1.27\% \\
|
| 280 |
Passes HLT & 34.3 & 97.6\% & 8.32 & 86.9\% & 14.1 & 86\% & 9.12 & 96.1\% \\
|
| 281 |
\Z mass window & 30.8 & 89.8\% & 7.31 & 87.9\% & 3.76 & 26.7\% & 8 & 87.8\% \\
|
| 282 |
\hline
|
| 283 |
Overall efficiency & & 16.7\% & & 0.00013\% & & 0.00045\% & & 0.0056\% \\
|
| 284 |
\hline
|
| 285 |
|
| 286 |
\multicolumn{9}{c}{ {\bf $2\mu1e$ Channel}} \\ \hline \hline
|
| 287 |
Step & $\WZ \to 2\mu1e$ & $ \epsilon$ & $\Z+jets$ & $ \epsilon$ & $t\bar{t}+jets$ & $ \epsilon$ & $b\bar{b}\ell\ell$ & $ \epsilon$\\ \hline
|
| 288 |
All events & 190 & & $5.82\cdot 10^6$ & & $8.27\cdot 10^5$ & & $1.44\cdot 10^5$ & \\
|
| 289 |
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\% \\
|
| 290 |
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\% \\
|
| 291 |
Found $\W \to e\nu$ & 44 & 58.5\% & 702 & 0.12\% & 15.1 & 0.54\% & 213 & 0.67\% \\
|
| 292 |
\W lepton $p_T$ cut & 38.4 & 87.2\% & 464 & 66.2\% & 10.3 & 68\% & 50.5 & 23.7\% \\
|
| 293 |
$\Delta R(e,\mu)$ cut & 38.4 & 99.9\% & 93 & 20\% & 7.15 & 69.6\% & 23.3 & 46\% \\
|
| 294 |
Passes HLT & 37.3 & 97.1\% & 88.8 & 95.5\% & 6.62 & 92.7\% & 23.1 & 99.4\% \\
|
| 295 |
\Z mass window & 33.6 & 90.1\% & 50.3 & 56.6\% & 2.84 & 42.9\% & 18.8 & 81.4\% \\
|
| 296 |
\hline
|
| 297 |
Overall efficiency & & 17.7\% & & 0.00086\% & & 0.00034\% & & 0.013\% \\
|
| 298 |
\hline
|
| 299 |
%\end{tabular}
|
| 300 |
%\begin{tabular}{lcc|cc|cc|cc|} \hline
|
| 301 |
\multicolumn{9}{c}{ {\bf $3\mu$ Channel}} \\ \hline \hline
|
| 302 |
Step & $\WZ \to 3\mu$ & $ \epsilon$ & $\Z+jets$ & $ \epsilon$ & $t\bar{t}+jets$ & $ \epsilon$ & $b\bar{b}\ell\ell$ & $ \epsilon$\\ \hline
|
| 303 |
All events & 189 & & $5.82\cdot 10^6$ & & $8.27\cdot 10^5$ & & $1.44\cdot 10^5$ & \\
|
| 304 |
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\% \\
|
| 305 |
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\% \\
|
| 306 |
Found $\W \to \mu\nu$ & 51.8 & 62\% & $2.52\cdot 10^3$ & 0.44\% & 34.8 & 1.25\% & 810 & 2.54\% \\
|
| 307 |
\W lepton $p_T$ cut & 42.5 & 81.9\% & 1.84 & 0.07\% & 1.16 & 3.33\% & 8.89 & 1.1\% \\
|
| 308 |
Passes HLT & 42.2 & 99.4\% & 1.84 & 100\% & 1.16 & 100\% & 8.89 & 100\% \\
|
| 309 |
\Z mass window & 38.5 & 91.1\% & 1.84 & 100\% & 1.16 & 100\% & 7.78 & 87.5\% \\
|
| 310 |
\hline
|
| 311 |
Overall efficiency & & 20.3\% & & 0.000032\% & & 0.00014\% & & 0.0054\% \\
|
| 312 |
\hline
|
| 313 |
\end{tabular}
|
| 314 |
|
| 315 |
\caption{Expected number of signal and background events passing the different
|
| 316 |
selections steps together with the efficiency of each requirement and total efficiency of
|
| 317 |
selection criteria in the \WZ, \Zbbbar, \Zjets and \ttjets samples for an integrated luminosity
|
| 318 |
of 1 \invfb.}
|
| 319 |
\label{tab:sel-effA}
|
| 320 |
\end{center}
|
| 321 |
\end{table}
|
| 322 |
|
| 323 |
|
| 324 |
|
| 325 |
\begin{table}
|
| 326 |
\begin{center}
|
| 327 |
\begin{tabular}{lcc|cc|cc|} \hline
|
| 328 |
\multicolumn{7}{c}{ {\bf $3e$ Channel}} \\ \hline \hline
|
| 329 |
Step & W+jets & $ \epsilon$ & ZZ & $ \epsilon$ & Zgamma & $ \epsilon$\\ \hline
|
| 330 |
All events & 5.64e+07 & & 1.61e+04 & & 2.16e+03 & \\
|
| 331 |
Found $Z \to ee$ & 1.28e+03 & 0.00227 \% & 387 & 2.41 \% & 635 & 29.4 \% \\
|
| 332 |
Second Z veto & 1.28e+03 & 100 \% & 380 & 98.1 \% & 635 & 100 \% \\
|
| 333 |
Found $W \to e$ & 5.8 & 0.454 \% & 9.68 & 2.55 \% & 21.4 & 3.37 \% \\
|
| 334 |
W Lepton Pt cut & 4.5 & 77.7 \% & 7.65 & 79 \% & 19.1 & 89.5 \% \\
|
| 335 |
Passes HLT & 4.5 & 100 \% & 7.65 & 100 \% & 18.9 & 98.9 \% \\
|
| 336 |
Z mass window & 1.29 & 28.7 \% & 6.87 & 89.8 \% & 16.6 & 87.7 \% \\
|
| 337 |
\hline
|
| 338 |
Overall efficiency & & 2.29e-06 \% & & 0.0427 \% & & 0.768 \% \\
|
| 339 |
\hline
|
| 340 |
\end{tabular}
|
| 341 |
\begin{tabular}{lcc|cc|cc|} \hline
|
| 342 |
\multicolumn{7}{c}{ {\bf $2e1\mu$ Channel}} \\ \hline \hline
|
| 343 |
Step & W+jets & $ \epsilon$ & ZZ & $ \epsilon$ & Zgamma & $ \epsilon$\\ \hline
|
| 344 |
All events & 5.64e+07 & & 1.61e+04 & & 2.16e+03 & \\
|
| 345 |
Found $Z \to ee$ & 1.28e+03 & 0.00227 \% & 387 & 2.41 \% & 635 & 29.4 \% \\
|
| 346 |
Second Z veto & 1.28e+03 & 100 \% & 380 & 98.1 \% & 635 & 100 \% \\
|
| 347 |
Found $W \to \mu$ & 7.51 & 0.588 \% & 8.59 & 2.26 \% & 3.14 & 0.494 \% \\
|
| 348 |
W Lepton Pt cut & 3.8 & 50.6 \% & 3.44 & 40 \% & 0.0296 & 0.943 \% \\
|
| 349 |
Passes HLT & 1.25 & 33 \% & 3.44 & 100 \% & 0.0296 & 100 \% \\
|
| 350 |
Z mass window & 1.25 & 100 \% & 3.44 & 100 \% & 0.0296 & 100 \% \\
|
| 351 |
\hline
|
| 352 |
Overall efficiency & & 2.22e-06 \% & & 0.0213 \% & & 0.00137 \% \\
|
| 353 |
\hline
|
| 354 |
\end{tabular}
|
| 355 |
|
| 356 |
\begin{tabular}{lcc|cc|cc|} \hline
|
| 357 |
\multicolumn{7}{c}{ {\bf $2\mu1e$ Channel}} \\ \hline \hline
|
| 358 |
Step & W+jets & $ \epsilon$ & ZZ & $ \epsilon$ & Zgamma & $ \epsilon$\\ \hline
|
| 359 |
All events & 5.64e+07 & & 1.61e+04 & & 2.16e+03 & \\
|
| 360 |
Found $Z \to \mu\mu$ & 60.1 & 0.000107 \% & 429 & 2.67 \% & 546 & 25.3 \% \\
|
| 361 |
Second Z veto & 60.1 & 100 \% & 423 & 98.6 \% & 546 & 100 \% \\
|
| 362 |
Found $W \to e$ & 0 & 0 \% & 11.6 & 2.73 \% & 17.4 & 3.2 \% \\
|
| 363 |
W Lepton Pt cut & 0 & 0 \% & 7.96 & 68.9 \% & 16.1 & 92.2 \% \\
|
| 364 |
$\Delta R(e,\mu)$ cut & 0 & 0 \% & 7.34 & 92.2 \% & 15.6 & 97.4 \% \\
|
| 365 |
Passes HLT & 0 & 0 \% & 7.34 & 100 \% & 15.1 & 96.3 \% \\
|
| 366 |
Z mass window & 0 & 0 \% & 6.25 & 85.1 \% & 13.3 & 88.4 \% \\
|
| 367 |
\hline
|
| 368 |
Overall efficiency & & 0 \% & & 0.0388 \% & & 0.617 \% \\
|
| 369 |
\hline
|
| 370 |
\end{tabular}
|
| 371 |
|
| 372 |
\begin{tabular}{lcc|cc|cc|} \hline
|
| 373 |
\multicolumn{7}{c}{ {\bf $3\mu$ Channel}} \\ \hline \hline
|
| 374 |
Step & W+jets & $ \epsilon$ & ZZ & $ \epsilon$ & Zgamma & $ \epsilon$\\ \hline
|
| 375 |
All events & 5.64e+07 & & 1.61e+04 & & 2.16e+03 & \\
|
| 376 |
Found $Z \to \mu\mu$ & 60.1 & 0.000107 \% & 429 & 2.67 \% & 546 & 25.3 \% \\
|
| 377 |
Second Z veto & 60.1 & 100 \% & 423 & 98.6 \% & 546 & 100 \% \\
|
| 378 |
Found $W \to \mu$ & 0 & 0 \% & 11.7 & 2.77 \% & 2.49 & 0.456 \% \\
|
| 379 |
W Lepton Pt cut & 0 & 0 \% & 4.53 & 38.7 \% & 0.00987 & 0.397 \% \\
|
| 380 |
Passes HLT & 0 & 0 \% & 4.53 & 100 \% & 0.00987 & 100 \% \\
|
| 381 |
Z mass window & 0 & 0 \% & 4.37 & 96.6 \% & 0.00987 & 100 \% \\
|
| 382 |
\hline
|
| 383 |
Overall efficiency & & 0 \% & & 0.0272 \% & & 0.000457 \% \\
|
| 384 |
\hline
|
| 385 |
\end{tabular}
|
| 386 |
|
| 387 |
\caption{Expected number of signal and background events passing the different
|
| 388 |
selections steps together with the efficiency of each requirement and total efficiency of
|
| 389 |
selection criteria in the \W + jets, \ZZ and \Zgamma samples for an integrated luminosity
|
| 390 |
of 1 \invfb.}
|
| 391 |
\label{tab:sel-effB}
|
| 392 |
\end{center}
|
| 393 |
\end{table}
|
| 394 |
|
| 395 |
\begin{table}[p]
|
| 396 |
\begin{center}
|
| 397 |
\begin{tabular}{l|ccccc}
|
| 398 |
\hline \hline
|
| 399 |
& \multicolumn{5}{c}{$\Z \to ee$ and \W decay modes below} \\
|
| 400 |
Reconstruction channel & $e \nu$
|
| 401 |
& $\mu \nu $
|
| 402 |
& $\tau \nu \to e \nu \nu $
|
| 403 |
& $\tau \nu \to \mu \nu \nu $
|
| 404 |
& $\tau \nu \to {\rm hadrons~} \nu$
|
| 405 |
\\ \hline
|
| 406 |
$3e$ & 17.4\% & 0.0319\% & 6.42\% & 0\% & 0.162\% \\
|
| 407 |
$2e1\mu$ & 0\% & 18.6\% & 0\% & 5.53\% & 0.0485\% \\
|
| 408 |
$2\mu1e$ & 0\% & 0\% & 0\% & 0\% & 0\% \\
|
| 409 |
$3\mu$ & 0\% & 0\% & 0\% & 0\% & 0\% \\
|
| 410 |
\hline \hline
|
| 411 |
|
| 412 |
& \multicolumn{5}{c}{$\Z \to \mu\mu$ and \W decay modes below} \\
|
| 413 |
Reconstruction channel & $e\nu$
|
| 414 |
& $\mu\nu$
|
| 415 |
& $\tau\nu \to e\nu\nu$
|
| 416 |
& $\tau\nu \to \mu\nu\nu$
|
| 417 |
& $\tau\nu \to {\rm hadrons~}\nu$
|
| 418 |
\\ \hline
|
| 419 |
$3e$ & 0\% & 0\% & 0\% & 0\% & 0\% \\
|
| 420 |
$2e1\mu$ & 0.0104\% & 0\% & 0\% & 0\% & 0\% \\
|
| 421 |
$2\mu1e$ & 19.6\% & 0.0208\% & 5.56\% & 0\% & 0.18\% \\
|
| 422 |
$3\mu$ & 0\% & 23.4\% & 0.0573\% & 6.77\% & 0.0164\% \\
|
| 423 |
\hline \hline
|
| 424 |
\end{tabular}
|
| 425 |
\end{center}
|
| 426 |
\caption{Selection efficiency for signal events in the four selection channels for the different
|
| 427 |
generated \W and \Z decay channels.}
|
| 428 |
\label{tab:wz-effimatrix}
|
| 429 |
|
| 430 |
%\end{table}
|
| 431 |
%\begin{table}[tbp]
|
| 432 |
\begin{center}
|
| 433 |
\begin{tabular}{llcc} \hline
|
| 434 |
& & \multicolumn{2}{c}{Generated decay} \\
|
| 435 |
& & \multicolumn{2}{c}{$\Z \to ee $} \\
|
| 436 |
Selection channel & & $\W \to e\nu$ & $\W \to \mu\nu$ \\
|
| 437 |
\hline \hline
|
| 438 |
\multicolumn{4}{c}{all} \\ \hline
|
| 439 |
$3e$ & all & 1644 events & 3 events \\
|
| 440 |
$3e$ & matched \Z & 93$\pm$1\% & 100\%\\
|
| 441 |
$3e$ & matched \W & 92$\pm$1\% & 0\\
|
| 442 |
$3e$ & matched \WZ & 91$\pm$1\% & 0\\
|
| 443 |
\hline \hline
|
| 444 |
|
| 445 |
\multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline
|
| 446 |
$3e$ & all & 1602 events & 0 events \\
|
| 447 |
$3e$ & matched \Z & 94$\pm$1\% & 0\\
|
| 448 |
$3e$ & matched \W & 92$\pm$1\% & 0\\
|
| 449 |
$3e$ & matched \WZ & 91$\pm$1\% & 0\\
|
| 450 |
\hline \hline
|
| 451 |
|
| 452 |
\multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline
|
| 453 |
$3e$ & all & 42 events & 3 events \\
|
| 454 |
$3e$ & matched \Z & 93$\pm$4\% & 100\%\\
|
| 455 |
$3e$ & matched \W & 91 $\pm$5\% & 0\\
|
| 456 |
$3e$ & matched \WZ & 91$\pm$5\% & 0\\
|
| 457 |
\hline \hline
|
| 458 |
|
| 459 |
\multicolumn{4}{c}{all} \\ \hline
|
| 460 |
$2e1\mu$ & all & 0 events & 1746 events \\
|
| 461 |
$2e1\mu$ & matched \Z & 0 & 100\%\\
|
| 462 |
$2e1\mu$ & matched \W & 0 & 100\%\\
|
| 463 |
$2e1\mu$ & matched \WZ & 0 & 100\%\\
|
| 464 |
\hline \hline
|
| 465 |
|
| 466 |
\multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline
|
| 467 |
$2e1\mu$ & all & 0 events & 1715 events \\
|
| 468 |
$2e1\mu$ & matched \Z & 0 & 100\%\\
|
| 469 |
$2e1\mu$ & matched \W & 0 & 100\%\\
|
| 470 |
$2e1\mu$ & matched \WZ & 0 & 100\%\\
|
| 471 |
\hline \hline
|
| 472 |
|
| 473 |
\multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline
|
| 474 |
$2e1\mu$ & all & 0 & 31 \\
|
| 475 |
$2e1\mu$ & matched \Z & 0 & 100\%\\
|
| 476 |
$2e1\mu$ & matched \W & 0 & 100\%\\
|
| 477 |
$2e1\mu$ & matched \WZ & 0 & 100\% \\ \hline \hline
|
| 478 |
\end{tabular}
|
| 479 |
\end{center}
|
| 480 |
\caption{Fractions of events with correctly matched leptons
|
| 481 |
to true decay product of \W and \Z decays for final states
|
| 482 |
with generated $\Z\to ee$ decays}
|
| 483 |
\label{tab:wz-matcheffi-Zee}
|
| 484 |
\end{table}
|
| 485 |
|
| 486 |
|
| 487 |
|
| 488 |
\begin{table}[tbp]
|
| 489 |
\begin{center}
|
| 490 |
\begin{tabular}{llcc} \hline
|
| 491 |
& & \multicolumn{2}{c}{Generated decay:} \\
|
| 492 |
& & \multicolumn{2}{c}{$\Z \to \mu\mu $} \\
|
| 493 |
Selection channel & & $\W \to e\nu$ & $\W \to \mu\nu$
|
| 494 |
\\
|
| 495 |
\hline \hline
|
| 496 |
\multicolumn{4}{c}{all} \\ \hline
|
| 497 |
$2\mu1e$ & all & 1895 events & 2 events \\
|
| 498 |
$2\mu1e$ & matched \Z & 100\% & 100\%\\
|
| 499 |
$2\mu1e$ & matched \W & 99$\pm$1\% & 0\\
|
| 500 |
$2\mu1e$ & matched \WZ & 99$\pm$1\% & 0\\
|
| 501 |
\hline \hline
|
| 502 |
|
| 503 |
\multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline
|
| 504 |
$2\mu1e$ & all & 1847 events & 0 events \\
|
| 505 |
$2\mu1e$ & matched \Z & 100\% & 0\\
|
| 506 |
$2\mu1e$ & matched \W & 99$\pm$1\% & 0\\
|
| 507 |
$2\mu1e$ & matched \WZ & 99$\pm$1\% & 0\\
|
| 508 |
\hline \hline
|
| 509 |
|
| 510 |
\multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline
|
| 511 |
$2\mu1e$ & all & 48 events & 2 events \\
|
| 512 |
$2\mu1e$ & matched \Z & 100\% & 100\%\\
|
| 513 |
$2\mu1e$ & matched \W & 94$\pm$3.5\%& 0\\
|
| 514 |
$2\mu1e$ & matched \WZ & 94$\pm$3.5\% & 0\\
|
| 515 |
\hline \hline
|
| 516 |
|
| 517 |
\multicolumn{4}{c}{all} \\ \hline
|
| 518 |
$3\mu$ & all & 0 events & 2251 events \\
|
| 519 |
$3\mu$ & matched \Z & 0 & 94$\pm$1\%\\
|
| 520 |
$3\mu$ & matched \W & 0 & 93$\pm$1\%\\
|
| 521 |
$3\mu$ & matched \WZ & 0 & 93$\pm$1\%\\
|
| 522 |
\hline \hline
|
| 523 |
|
| 524 |
\multicolumn{4}{c}{exactly 1 \W lepton candidate} \\ \hline
|
| 525 |
$3\mu$ & all & 0 events & 2207 events \\
|
| 526 |
$3\mu$ & matched \Z & 0 & 94$\pm$1\%\\
|
| 527 |
$3\mu$ & matched \W & 0 & 93$\pm$1\%\\
|
| 528 |
$3\mu$ & matched \WZ & 0 & 93$\pm$1\%\\
|
| 529 |
\hline \hline
|
| 530 |
|
| 531 |
\multicolumn{4}{c}{more than 1 \W lepton candidate} \\ \hline
|
| 532 |
$3\mu$ & all & 0 events & 44 events \\
|
| 533 |
$3\mu$ & matched \Z & 0 & 91$\pm$4\%\\
|
| 534 |
$3\mu$ & matched \W & 0 & 91$\pm$4\%\\
|
| 535 |
$3\mu$ & matched \WZ & 0 & 91$\pm$4\%\\ \hline \hline
|
| 536 |
\end{tabular}
|
| 537 |
\end{center}
|
| 538 |
\caption{Fractions of MC \WZ events with correctly matched leptons
|
| 539 |
to true decay product of \W and \Z decays for final states
|
| 540 |
with generated $\Z\to \mu\mu$ decays}
|
| 541 |
\label{tab:wz-matcheffi-Zmumu}
|
| 542 |
\end{table}
|
| 543 |
|
| 544 |
|
| 545 |
\subsection{Complementary studies: can we use the neutrino?}
|
| 546 |
|
| 547 |
In $\WZ \to \ell^{\pm}\nu \ellell (\ell=e,\mu)$ events, the neutrino
|
| 548 |
coming from the \W-boson decay leaves the detector with a significant
|
| 549 |
amount of energy, which should reflect in a large transverse missing
|
| 550 |
energy measurement. On the other side, no large MET is expected for
|
| 551 |
the most important background categories, especially \Zjets,
|
| 552 |
\Zbbbar, \ZZ and \Zgamma. This expectation is confirmed, as can be
|
| 553 |
seen in Figure~\ref{fig:met}.
|
| 554 |
|
| 555 |
\begin{figure}[bt]
|
| 556 |
\begin{center}
|
| 557 |
\scalebox{0.8}{\includegraphics{figs/met_by_channel.eps}}
|
| 558 |
\caption{Missing transverse energy for the four signal categories.
|
| 559 |
The distributions show the number of expected events
|
| 560 |
for $1 fb^{-1}$. Only events with 81 GeV $< M_Z < $ 101 \gev
|
| 561 |
are shown. All selection cuts are applied.}
|
| 562 |
\label{fig:met}
|
| 563 |
\end{center}
|
| 564 |
\end{figure}
|
| 565 |
|
| 566 |
\begin{figure}[bt]
|
| 567 |
\begin{center}
|
| 568 |
\scalebox{0.8}{\includegraphics{figs/mtw_by_channel.eps}}
|
| 569 |
\caption{\W transverse mass for the four signal categories.
|
| 570 |
The distributions show the number of expected events
|
| 571 |
for $1 fb^{-1}$. Only events with 81 GeV $< M_Z < $ 101 GeV are shown.
|
| 572 |
All selection cuts are applied.}
|
| 573 |
\label{fig:mtw}
|
| 574 |
\end{center}
|
| 575 |
\end{figure}
|
| 576 |
|
| 577 |
|
| 578 |
Another variable sensitive to the presence of the neutrino
|
| 579 |
is the W transverse mass $m_T^W$, obtained by combining the missing
|
| 580 |
energy vector and the lepton associated to the \W-boson decay.
|
| 581 |
The distribution of $m_T^W$ is shown in Figure~\ref{fig:mtw}.
|
| 582 |
The signal yield could be extracted from that distribution.
|
| 583 |
This requires however additional studies and it has not been
|
| 584 |
done at this stage.
|
| 585 |
|
| 586 |
%\subsection{Signal extraction}
|
| 587 |
%\input D0Matrix
|
| 588 |
\input zjetbackground
|
| 589 |
|
| 590 |
|
| 591 |
\section{Systematic uncertainties}
|
| 592 |
\label{sec:systematic}
|
| 593 |
\input Sys
|
| 594 |
|
| 595 |
|
| 596 |
|
| 597 |
|
| 598 |
|
| 599 |
|
| 600 |
|
