| 57 |
|
An additional isolation criterion requires that the energy |
| 58 |
|
measured in the calorimeters within a $\Delta R = 0.3$ cone around the |
| 59 |
|
muon must be smaller than 3 GeV and the sum of the $p_t$ of tracks |
| 60 |
< |
within a $\Delta R = 0.35$ cone around the muon must be smaller than 2.5 |
| 60 |
> |
within a $\Delta R = 0.25$ cone around the muon must be smaller than 2 |
| 61 |
|
GeV. These cuts reduce the background from muons originated in |
| 62 |
|
\b-quark decays of the $\Zbbbar$ background, which are close to tracks |
| 63 |
|
and clusters from the other \b-quark decay products. |
| 67 |
|
%variables for the $\Z\b\bbar(\epem\b\bbar)$ is particularly |
| 68 |
|
%interesting, since muons only stem from \b-quark decays. |
| 69 |
|
|
| 70 |
+ |
The significance of the muon impact parameter in the plane |
| 71 |
+ |
transverse to the beam, $S_{IP}$, discriminates against leptons from |
| 72 |
+ |
heavy-quark decays in all Standard Model background processes. This |
| 73 |
+ |
variable is defined as the ratio between the measured impact parameter |
| 74 |
+ |
and its uncertainty: $S_{IP}=IP/\sigma_{IP}$, and is required to |
| 75 |
+ |
satisfy $S_{IP}<3$. This requirement is applied only for muons |
| 76 |
+ |
and not for electrons. For electrons, the dominant background |
| 77 |
+ |
comes from fake electrons and not from heavy quark decays. |
| 78 |
+ |
|
| 79 |
+ |
|
| 80 |
|
|
| 81 |
|
\subsection{\WZ candidate selection} |
| 82 |
|
|
| 83 |
|
Events are accepted if they contain at least three charged leptons, |
| 84 |
< |
either electrons or muons, with $p_t > 10\,\mathrm{GeV}$ and $| \eta | < 2.5$, as |
| 85 |
< |
discussed in~\ref{sec:leptonId}. |
| 84 |
> |
either electrons or muons, with $p_t > 15\,\mathrm{GeV}$ and $| \eta | < 2.5$ for |
| 85 |
> |
electrons,$| \eta | < 2.4$ for muons. |
| 86 |
> |
as discussed in~\ref{sec:leptonId}. |
| 87 |
|
|
| 88 |
|
The \WZ candidate selection proceeds from building all possible |
| 89 |
|
\Z-boson candidates from same-flavour opposite-charge lepton pairs. |
| 115 |
|
the range that maximises the significance as shown in |
| 116 |
|
Figure~\ref{fig:s_vs_wlpt}. |
| 117 |
|
|
| 107 |
– |
|
| 118 |
|
The expected number of events passing the various steps of the selection |
| 119 |
|
is listed in Tables~\ref{tab:sel-effA} and~\ref{tab:sel-effB}. |
| 120 |
|
Table~\ref{tab:wz-effimatrix} lists the final selection efficiency for |
| 127 |
|
to the \pt cut on the third lepton, since the \pt spectrum of electrons or |
| 128 |
|
muons from $W \to \tau \to e/\mu$ decays is softer. |
| 129 |
|
|
| 130 |
+ |
\begin{table}[p] |
| 131 |
+ |
\begin{center} |
| 132 |
+ |
|
| 133 |
+ |
\begin{tabular}{lcccc} \hline |
| 134 |
+ |
Step & WZ & Z+jets & TTbar+jets & bbll\\ \hline |
| 135 |
+ |
All events & 546 & 1.2679e+06 & 17556.1 & 72770.4 \\ |
| 136 |
+ |
Found $Z \to ee$ & 219.517 (40.2045 \%) & 520695 (41.0674 \%) & 3474.61 (19.7914 \%) & 29563.3 (40.6254 \%) \\ |
| 137 |
+ |
Z loose electron ID & 219.517 (100 \%) & 520695 (100 \%) & 3474.61 (100 \%) & 29563.3 (100 \%) \\ |
| 138 |
+ |
Z Lepton Pt cut & 216.371 (98.5671 \%) & 515556 (99.0131 \%) & 3289.22 (94.6645 \%) & 29109.9 (98.4665 \%) \\ |
| 139 |
+ |
Z Lepton $eta$ cut & 216.371 (100 \%) & 515556 (100 \%) & 3289.22 (100 \%) & 29109.9 (100 \%) \\ |
| 140 |
+ |
Z Lepton IP cut & 206.797 (95.5751 \%) & 492205 (95.4707 \%) & 3011.11 (91.5448 \%) & 27833.5 (95.6153 \%) \\ |
| 141 |
+ |
Found $W \to e$ & 42.8968 (20.7434 \%) & 301.116 (0.061177 \%) & 14.8797 (0.494158 \%) & 173.054 (0.621745 \%) \\ |
| 142 |
+ |
W Lepton $\eta$ cut & 42.8968 (100 \%) & 301.116 (100 \%) & 14.8797 (100 \%) & 173.054 (100 \%) \\ |
| 143 |
+ |
W Lepton Pt cut & 35.6425 (83.0889 \%) & 86.9864 (28.8879 \%) & 9.30549 (62.5383 \%) & 23.9385 (13.833 \%) \\ |
| 144 |
+ |
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\%) \\ |
| 147 |
+ |
\hline |
| 148 |
+ |
\end{tabular} |
| 149 |
+ |
|
| 150 |
+ |
|
| 151 |
+ |
\begin{tabular}{lcccc} \hline |
| 152 |
+ |
Step & WZ & Z+jets & TTbar+jets & bbll\\ \hline |
| 153 |
+ |
All events & 546 & 1.2679e+06 & 17556.1 & 72770.4 \\ |
| 154 |
+ |
Found $Z \to ee$ & 219.517 (40.2045 \%) & 520695 (41.0674 \%) & 3474.61 (19.7914 \%) & 29563.3 (40.6254 \%) \\ |
| 155 |
+ |
Z electron ID loose & 219.517 (100 \%) & 520695 (100 \%) & 3474.61 (100 \%) & 29563.3 (100 \%) \\ |
| 156 |
+ |
Z Lepton Pt cut & 216.371 (98.5671 \%) & 515556 (99.0131 \%) & 3289.22 (94.6645 \%) & 29109.9 (98.4665 \%) \\ |
| 157 |
+ |
Z Lepton $eta$ cut & 216.371 (100 \%) & 515556 (100 \%) & 3289.22 (100 \%) & 29109.9 (100 \%) \\ |
| 158 |
+ |
Z Lepton IP cut & 206.797 (95.5751 \%) & 492205 (95.4707 \%) & 3011.11 (91.5448 \%) & 27833.5 (95.6153 \%) \\ |
| 159 |
+ |
Found $W \to \mu$ & 57.1892 (27.6547 \%) & 5982.86 (1.21552 \%) & 815.122 (27.0705 \%) & 3808.22 (13.6821 \%) \\ |
| 160 |
+ |
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 \%) \\ |
| 165 |
+ |
\hline |
| 166 |
+ |
\end{tabular} |
| 167 |
+ |
|
| 168 |
+ |
\begin{tabular}{lcccc} \hline |
| 169 |
+ |
Step & WZ & Z+jets & TTbar+jets & bbll\\ \hline |
| 170 |
+ |
All events & 546 & 1.2679e+06 & 17556.1 & 72770.4 \\ |
| 171 |
+ |
Found $Z \to \mu\mu$ & 326.484 (59.7955 \%) & 748256 (59.0152 \%) & 14081.6 (80.2087 \%) & 43207.1 (59.3746 \%) \\ |
| 172 |
+ |
Z muon isolation & 282.27 (86.4575 \%) & 669556 (89.4822 \%) & 4201.52 (29.837 \%) & 37959.1 (87.8538 \%) \\ |
| 173 |
+ |
Z Lepton $eta$ cut & 282.27 (100 \%) & 669547 (99.9987 \%) & 4200.47 (99.975 \%) & 37959.1 (99.9998 \%) \\ |
| 174 |
+ |
Z Lepton Pt cut & 274.249 (97.1584 \%) & 657267 (98.1659 \%) & 3626.81 (86.3429 \%) & 36945.8 (97.3306 \%) \\ |
| 175 |
+ |
Z Lepton IP cut & 249.792 (91.0824 \%) & 603257 (91.7827 \%) & 3125.35 (86.1737 \%) & 33937.7 (91.8581 \%) \\ |
| 176 |
+ |
Found $W \to e$ & 51.9401 (20.7933 \%) & 797.766 (0.132243 \%) & 20.4415 (0.654055 \%) & 228.342 (0.672826 \%) \\ |
| 177 |
+ |
W Lepton $\eta$ cut & 51.9401 (100 \%) & 797.766 (100 \%) & 20.4415 (100 \%) & 228.342 (100 \%) \\ |
| 178 |
+ |
W tight electron ID & 51.9401 (100 \%) & 797.766 (100 \%) & 20.4415 (100 \%) & 228.342 (100 \%) \\ |
| 179 |
+ |
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 \%) \\ |
| 182 |
+ |
\hline |
| 183 |
+ |
\end{tabular} |
| 184 |
+ |
|
| 185 |
+ |
\begin{tabular}{lcccc} \hline |
| 186 |
+ |
Step & WZ & Z+jets & TTbar+jets & bbll\\ \hline |
| 187 |
+ |
All events & 546 & 1.2679e+06 & 17556.1 & 72770.4 \\ |
| 188 |
+ |
Found $Z \to \mu\mu$ & 326.484 (59.7955 \%) & 748256 (59.0152 \%) & 14081.6 (80.2087 \%) & 43207.1 (59.3746 \%) \\ |
| 189 |
+ |
Z muon isolation & 282.27 (86.4575 \%) & 669556 (89.4822 \%) & 4201.52 (29.837 \%) & 37959.1 (87.8538 \%) \\ |
| 190 |
+ |
Z Lepton $eta$ cut & 282.27 (100 \%) & 669547 (99.9987 \%) & 4200.47 (99.975 \%) & 37959.1 (99.9998 \%) \\ |
| 191 |
+ |
Z Lepton Pt cut & 274.249 (97.1584 \%) & 657267 (98.1659 \%) & 3626.81 (86.3429 \%) & 36945.8 (97.3306 \%) \\ |
| 192 |
+ |
Z Lepton IP cut & 249.792 (91.0824 \%) & 603257 (91.7827 \%) & 3125.35 (86.1737 \%) & 33937.7 (91.8581 \%) \\ |
| 193 |
+ |
Found $W \to \mu$ & 73.015 (29.2303 \%) & 7135.7 (1.18286 \%) & 774.076 (24.7677 \%) & 4435.51 (13.0696 \%) \\ |
| 194 |
+ |
W Lepton $\eta$ cut & 72.956 (99.9192 \%) & 7110.07 (99.6409 \%) & 774.076 (100 \%) & 4432.32 (99.9282 \%) \\ |
| 195 |
+ |
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 \%) \\ |
| 199 |
+ |
\hline |
| 200 |
+ |
\end{tabular} |
| 201 |
+ |
\caption{Expected number of signal and background events passing the different |
| 202 |
+ |
selections steps in the \WZ, \ttbar and \Zbbbar samples for an integrated luminosity |
| 203 |
+ |
of 1 \invfb.} |
| 204 |
+ |
\label{tab:sel-effA} |
| 205 |
+ |
\end{center} |
| 206 |
+ |
\end{table} |
| 207 |
+ |
|
| 208 |
+ |
|
| 209 |
|
|
| 210 |
|
\subsection{Signal extraction} |
| 211 |
|
|
| 214 |
|
|
| 215 |
|
|
| 216 |
|
|
| 217 |
+ |
\begin{figure}[bt] |
| 218 |
+ |
\begin{center} |
| 219 |
+ |
\scalebox{0.8}{\includegraphics{figs/mtw_by_channel.eps}} |
| 220 |
+ |
\caption{W transverse mass for the four signal categories. |
| 221 |
+ |
The distributions show the number of expected events |
| 222 |
+ |
for $1 fb^{-1}$. Only events with 81.1 GeV $< M_Z < $ 101.1 GeV are shown.} |
| 223 |
+ |
\label{fig:mtw} |
| 224 |
+ |
\end{center} |
| 225 |
+ |
\end{figure} |
