ViewVC Help
View File | Revision Log | Show Annotations | Root Listing
root/cvsroot/UserCode/benhoob/cmsnotes/StopSearch/CR4.tex
Revision: 1.8
Committed: Wed Oct 10 21:04:19 2012 UTC (12 years, 7 months ago) by linacre
Content type: application/x-tex
Branch: MAIN
Changes since 1.7: +18 -13 lines
Log Message:
changed met cut for jet multiplicty plot and SFs from 100 to 50 GeV

File Contents

# User Rev Content
1 claudioc 1.1 \subsection{Dilepton studies in CR4}
2     \label{sec:cr4}
3    
4     \subsubsection{Modeling of Additional Hard Jets in Top Dilepton Events}
5     \label{sec:jetmultiplicity}
6    
7     [THIS SUBSUBSECTION IS DONE...MODULO THE LATEST PLOTS AND THE LATEST
8     NUMBERS IN THE TABLE]
9    
10     Dilepton \ttbar\ events have 2 jets from the top decays, so additional
11     jets from radiation or higher order contributions are required to
12 linacre 1.8 enter the signal sample. The modeling of additional jets in \ttbar\
13 claudioc 1.1 events is checked in a \ttll\ control sample,
14     selected by requiring
15     \begin{itemize}
16     \item exactly 2 selected electrons or muons with \pt $>$ 20 GeV
17 linacre 1.8 \item \met\ $>$ 50 GeV
18 claudioc 1.1 \item $\geq1$ b-tagged jet
19 burkett 1.2 \item Z-veto ($|m_{\ell\ell} - 91| > 15$ GeV)
20 claudioc 1.1 \end{itemize}
21     Figure~\ref{fig:dileptonnjets} shows a comparison of the jet
22     multiplicity distribution in data and MC for this two-lepton control
23     sample. After requiring at least 1 b-tagged jet, most of the
24     events have 2 jets, as expected from the dominant process \ttll. There is also a
25     significant fraction of events with additional jets.
26     The 3-jet sample is mainly comprised of \ttbar\ events with 1 additional
27     emission and similarly the $\ge4$-jet sample contains primarily
28     $\ttbar+\ge2$ jet events.
29     %Even though the primary \ttbar\
30     %Madgraph sample used includes up to 3 additional partons at the Matrix
31     %Element level, which are intended to describe additional hard jets,
32     %Figure~\ref{fig:dileptonnjets} shows a slight mis-modeling of the
33     %additional jets.
34    
35    
36     \begin{figure}[hbt]
37     \begin{center}
38 linacre 1.8 \includegraphics[width=0.5\linewidth]{plots/njets_all_met50_mueg.pdf}
39     \includegraphics[width=0.5\linewidth]{plots/njets_all_met50_diel.pdf}%
40     \includegraphics[width=0.5\linewidth]{plots/njets_all_met50_dimu.pdf}
41 claudioc 1.1 \caption{
42     \label{fig:dileptonnjets}%\protect
43     Comparison of the jet multiplicity distribution in data and MC for dilepton events in the \E-\M\
44     (top), \E-\E\ (bottom left) and \M-\M\ (bottom right) channels.}
45     \end{center}
46     \end{figure}
47    
48     It should be noted that in the case of \ttll\ events
49     with a single reconstructed lepton, the other lepton may be
50     mis-reconstructed as a jet. For example, a hadronic tau may be
51     mis-identified as a jet (since no $\tau$ identification is used).
52     In this case only 1 additional jet from radiation may suffice for
53     a \ttll\ event to enter the signal sample. As a result, both the
54     samples with $\ttbar+1$ jet and $\ttbar+\ge2$ jets are relevant for
55 burkett 1.2 estimating the top dilepton background in the signal region.
56 claudioc 1.1
57     %In this section we discuss a correction to $ N_{2 lep}^{MC} $ in Equation XXX
58     %due to differences in the modelling of the jet multiplicity in data versus MC.
59     %The same correction also enters $ N_{peak}^{MC}$ in Equation XXX to the extend that the
60     %dilepton contributions to $ N_{peak}^{MC}$ gets corrected.
61    
62     %The dilepton control sample is defined by the following requirements:
63     %\begin{itemize}
64     %\item Exactly 2 selected electrons or muons with \pt $>$ 20 GeV
65     %\item \met\ $>$ 50 GeV
66     %\item $\geq1$ b-tagged jet
67     %\end{itemize}
68     %
69     %This sample is dominated by \ttll. The distribution of \njets\ for data and MC passing this selection is displayed in Fig.~\ref{fig:dilepton_njets}.
70     %We use this distribution to derive scale factors which reweight the \ttll\ MC \njets\ distribution to match the data. We define the following
71     %quantities
72     %
73     %\begin{itemize}
74     %\item $N_{2}=$ data yield minus non-dilepton \ttbar\ MC yield for \njets\ $\leq$ 2
75     %\item $N_{3}=$ data yield minus non-dilepton \ttbar\ MC yield for \njets\ = 3
76     %\item $N_{4}=$ data yield minus non-dilepton \ttbar\ MC yield for \njets\ $\geq$ 4
77     %\item $M_{2}=$ dilepton \ttbar\ MC yield for \njets\ $\leq$ 2
78     %\item $M_{3}=$ dilepton \ttbar\ MC yield for \njets\ = 3
79     %\item $M_{4}=$ dilepton \ttbar\ MC yield for \njets\ $\geq$ 4
80     %\end{itemize}
81     %
82     %We use these yields to define 3 scale factors, which quantify the data/MC ratio in the 3 \njets\ bins:
83     %
84     %\begin{itemize}
85     %\item $SF_2 = N_2 / M_2$
86     %\item $SF_3 = N_3 / M_3$
87     %\item $SF_4 = N_4 / M_4$
88     %\end{itemize}
89     %
90     %And finally, we define the scale factors $K_3$ and $K_4$:
91     %
92     %\begin{itemize}
93     %\item $K_3 = SF_3 / SF_2$
94     %\item $K_4 = SF_4 / SF_2$
95     %\end{itemize}
96     %
97     %The scale factor $K_3$ is extracted from dilepton \ttbar\ events with \njets = 3, which have exactly 1 ISR jet.
98     %The scale factor $K_4$ is extracted from dilepton \ttbar\ events with \njets $\geq$ 4, which have at least 2 ISR jets.
99     %Both of these scale factors are needed since dilepton \ttbar\ events which fall in our signal region (including
100     %the \njets $\geq$ 4 requirement) may require exactly 1 ISR jet, in the case that the second lepton is reconstructed
101     %as a jet, or at least 2 ISR jets, in the case that the second lepton is not reconstructed as a jet. These scale
102     %factors are applied to the dilepton \ttbar\ MC only. For a given MC event, we determine whether to use $K_3$ or $K_4$
103     %by counting the number of reconstructed jets in the event ($N_{\rm{jets}}^R$) , and subtracting off any reconstructed
104     %jet which is matched to the second lepton at generator level ($N_{\rm{jets}}^\ell$); $N_{\rm{jets}}^{\rm{cor}} = N_{\rm{jets}}^R - N_{\rm{jets}}^\ell$.
105     %For events with $N_{\rm{jets}}^{\rm{cor}}=3$ the factor $K_3$ is applied, while for events with $N_{\rm{jets}}^{\rm{cor}}\geq4$ the factor $K_4$ is applied.
106     %For all subsequent steps, the scale factors $K_3$ and $K_4$ have been
107     %applied to the \ttll\ MC.
108    
109    
110     Table~\ref{tab:njetskfactors} shows scale factors ($K_3$ and $K_4$)
111     used to correct the
112     fraction of events with additional jets in MC to the observed fraction
113     in data. These scale factors are calculated from Fig.~\ref{fig:dileptonnjets}
114     as follows:
115     \begin{itemize}
116     \item $N_{2}=$ data yield minus non-dilepton \ttbar\ MC yield for \njets\ $\leq$ 2
117     \item $N_{3}=$ data yield minus non-dilepton \ttbar\ MC yield for \njets\ = 3
118     \item $N_{4}=$ data yield minus non-dilepton \ttbar\ MC yield for \njets\ $\geq$ 4
119     \item $M_{2}=$ dilepton \ttbar\ MC yield for \njets\ $\leq$ 2
120     \item $M_{3}=$ dilepton \ttbar\ MC yield for \njets\ = 3
121     \item $M_{4}=$ dilepton \ttbar\ MC yield for \njets\ $\geq$ 4
122     \end{itemize}
123     \noindent then
124     \begin{itemize}
125     \item $SF_2 = N_2 / M_2$
126     \item $SF_3 = N_3 / M_3$
127     \item $SF_4 = N_4 / M_4$
128     \item $K_3 = SF_3 / SF_2$
129     \item $K_4 = SF_4 / SF_2$
130     \end{itemize}
131     \noindent This insures that $K_3 M_3/(M_2 + K_3 M_3 + K_4 M_4) = N_3 /
132     (N_2+N_3+N_4)$ and similarly for the $\geq 4$ jet bin.
133    
134 linacre 1.8 Table~\ref{tab:njetskfactors} also shows the values of $K_3$ and $K_4$ when the \met\ cut in the control sample definition is changed from 50 GeV to 100 GeV and 150 GeV.
135     These values of $K_3$ and $K_4$ are not used in the analysis, but demonstrate that there is no statistically significant dependence of $K_3$ and $K_4$ on the \met\ cut.
136 claudioc 1.1
137 linacre 1.8
138     The factors $K_3$ and $K_4$ (derived with the 50 GeV \met\ cut) are applied to the \ttll\ MC throughout the
139 claudioc 1.1 entire analysis, i.e.
140     whenever \ttll\ MC is used to estimate or subtract
141     a yield or distribution.
142     %
143     In order to do so, it is first necessary to count the number of
144     additional jets from radiation and exclude leptons mis-identified as
145     jets. A jet is considered a mis-identified lepton if it is matched to a
146     generator-level second lepton with sufficient energy to satisfy the jet
147     \pt\ requirement ($\pt>30~\GeV$). Then \ttll\ events that need two
148     radiation jets to enter our selection are scaled by $K_4$,
149     while those that only need one radiation jet are scaled by $K_3$.
150    
151     \begin{table}[!ht]
152     \begin{center}
153 linacre 1.8 \begin{tabular}{l|c|c|c}
154     \cline{2-4}
155     & \multicolumn{3}{c}{ \met\ cut for Data/MC Scale Factor} \\
156 claudioc 1.1 \hline
157 linacre 1.8 Jet Multiplicity Sample & 50 GeV & 100 GeV & 150 GeV \\
158 claudioc 1.1 \hline
159     \hline
160 linacre 1.8 N jets $= 3$ (sensitive to $\ttbar+1$ extra jet from radiation)
161     & $K_3 = 0.98 \pm 0.02$ & $K_3 = 1.01 \pm 0.03$ & $K_3 = 1.00 \pm 0.08$ \\
162 claudioc 1.1 N jets $\ge4$ (sensitive to $\ttbar+\ge2$ extra jets from radiation)
163 linacre 1.8 & $K_4 = 0.94 \pm 0.02$ & $K_4 = 0.93 \pm 0.04$ & $K_4 = 1.00 \pm 0.08$ \\
164 claudioc 1.1 \hline
165     \end{tabular}
166     \caption{Data/MC scale factors used to account for differences in the
167     fraction of events with additional hard jets from radiation in
168 linacre 1.8 \ttll\ events. The values derived with the 50 GeV \met\ cut are applied
169     to the \ttll\ MC throughout the analysis. \label{tab:njetskfactors}}
170 claudioc 1.1 \end{center}
171     \end{table}
172    
173     \clearpage
174    
175    
176    
177     \subsubsection{Validation of the ``Physics'' Modelling of the \ttdl\
178     MC in CR4}
179 burkett 1.2 \label{sec:CR4-valid}
180 claudioc 1.1
181     [THE TEXT IN THIS SUBSECTION IS ESSENTIALLY COMPLETE]
182    
183     As mentioned above, $t\bar{t} \to $ dileptons where one of the leptons
184     is somehow lost constitutes the main background.
185     The object of this test is to validate the $M_T$ distribution of this
186     background by looking at the $M_T$ distribution of well identified
187     dilepton events.
188     We construct a transverse mass variable from the leading lepton and
189 vimartin 1.4 the \met. We distinguish between events with leading electrons and
190 claudioc 1.1 leading muons.
191    
192     The $t\bar{t}$ MC is corrected using the $K_3$ and $K_4$ factors
193     from Section~\ref{sec:jetmultiplicity}. It is also normalized to the
194     total data yield separately for the \met\ requirements of signal
195     regions A, B, C, and D. These normalization factors are listed
196     in Table~\ref{tab:cr4mtsf} and are close to unity.
197    
198     The underlying \met\ and $M_T$ distributions are shown in
199 burkett 1.2 Figures~\ref{fig:cr4met} and~\ref{fig:cr4mtrest}. The data-MC agreement
200 claudioc 1.1 is quite good. Quantitatively, this is also shown in Table~\ref{tab:cr4yields}.
201    
202    
203     \begin{table}[!h]
204     \begin{center}
205 vimartin 1.3 {\footnotesize
206 vimartin 1.6 \begin{tabular}{l||c||c|c|c|c|c|c}
207 claudioc 1.1 \hline
208 vimartin 1.3 Sample & CR4PRESEL & CR4A & CR4B & CR4C &
209 vimartin 1.6 CR4D & CR4E & CR4F\\
210 claudioc 1.1 \hline
211     \hline
212 vimartin 1.6 $\mu$ Data/MC-SF & $1.01 \pm 0.03$ & $0.96 \pm 0.04$ & $0.99 \pm 0.07$ & $1.05 \pm 0.13$ & $0.91 \pm 0.20$ & $1.10 \pm 0.34$ & $1.50 \pm 0.67$ \\
213 claudioc 1.1 \hline
214     \hline
215 vimartin 1.6 e Data/MC-SF & $0.99 \pm 0.03$ & $0.99 \pm 0.05$ & $0.91 \pm 0.08$ & $0.84 \pm 0.13$ & $0.70 \pm 0.18$ & $0.73 \pm 0.29$ & $0.63 \pm 0.38$ \\
216 claudioc 1.1 \hline
217 vimartin 1.3 \end{tabular}}
218 claudioc 1.1 \caption{ Data/MC scale factors for total yields, applied to compare
219     the shapes of the distributions.
220     The uncertainties are statistical only.
221     \label{tab:cr4mtsf}}
222     \end{center}
223     \end{table}
224    
225    
226     \begin{table}[!h]
227     \begin{center}
228 vimartin 1.3 {\footnotesize
229 vimartin 1.6 \begin{tabular}{l||c||c|c|c|c|c|c}
230 claudioc 1.1 \hline
231 vimartin 1.3 Sample & CR4PRESEL & CR4A & CR4B & CR4C &
232 vimartin 1.6 CR4D & CR4E & CR4F\\
233 claudioc 1.1 \hline
234     \hline
235 vimartin 1.7 $\mu$ MC & $256 \pm 14$ & $152 \pm 11$ & $91 \pm 9$ & $26 \pm 5$ & $6 \pm 2$ & $4 \pm 2$ & $2 \pm 1$ \\
236 vimartin 1.6 $\mu$ Data & $251$ & $156$ & $98$ & $27$ & $8$ & $6$ & $4$ \\
237 claudioc 1.1 \hline
238 vimartin 1.7 $\mu$ Data/MC SF & $0.98 \pm 0.08$ & $1.02 \pm 0.11$ & $1.08 \pm 0.16$ & $1.04 \pm 0.28$ & $1.29 \pm 0.65$ & $1.35 \pm 0.80$ & $2.10 \pm 1.72$ \\
239 claudioc 1.1 \hline
240     \hline
241 vimartin 1.7 e MC & $227 \pm 13$ & $139 \pm 11$ & $73 \pm 8$ & $21 \pm 4$ & $5 \pm 2$ & $2 \pm 1$ & $1 \pm 1$ \\
242 vimartin 1.6 e Data & $219$ & $136$ & $72$ & $19$ & $2$ & $1$ & $1$ \\
243 claudioc 1.1 \hline
244 vimartin 1.7 e Data/MC SF & $0.96 \pm 0.09$ & $0.98 \pm 0.11$ & $0.99 \pm 0.16$ & $0.92 \pm 0.29$ & $0.41 \pm 0.33$ & $0.53 \pm 0.62$ & $0.76 \pm 0.96$ \\
245     \hline
246     \hline
247     $\mu$+e MC & $483 \pm 19$ & $291 \pm 16$ & $164 \pm 13$ & $47 \pm 7$ & $11 \pm 3$ & $6 \pm 2$ & $3 \pm 2$ \\
248     $\mu$+e Data & $470$ & $292$ & $170$ & $46$ & $10$ & $7$ & $5$ \\
249     \hline
250     $\mu$+e Data/MC SF & $0.97 \pm 0.06$ & $1.00 \pm 0.08$ & $1.04 \pm 0.11$ & $0.99 \pm 0.20$ & $0.90 \pm 0.37$ & $1.11 \pm 0.57$ & $1.55 \pm 1.04$ \\
251 claudioc 1.1 \hline
252 vimartin 1.3 \end{tabular}}
253 claudioc 1.1 \caption{ Yields in \mt\ tail comparing the MC prediction (after
254     applying SFs) to data. The uncertainties are statistical only.
255     \label{tab:cr4yields}}
256     \end{center}
257     \end{table}
258    
259     \begin{figure}[hbt]
260     \begin{center}
261     \includegraphics[width=0.5\linewidth]{plots/CR4plots/met_met50_leadmuo_nj4.pdf}%
262     \includegraphics[width=0.5\linewidth]{plots/CR4plots/met_met50_leadele_nj4.pdf}
263     \includegraphics[width=0.5\linewidth]{plots/CR4plots/mt_met100_leadmuo_nj4.pdf}%
264     \includegraphics[width=0.5\linewidth]{plots/CR4plots/mt_met100_leadele_nj4.pdf}
265     \caption{
266     Comparison of the \met\ (top) and \mt\ for $\met>100$ (bottom) distributions in data vs. MC for events
267     with a leading muon (left) and leading electron (right)
268     satisfying the requirements of CR4.
269     \label{fig:cr4met}
270     }
271     \end{center}
272     \end{figure}
273    
274     \begin{figure}[hbt]
275     \begin{center}
276 vimartin 1.3 \includegraphics[width=0.5\linewidth]{plots/CR4plots/mt_met50_leadmuo_nj4.pdf}%
277     \includegraphics[width=0.5\linewidth]{plots/CR4plots/mt_met50_leadele_nj4.pdf}
278 claudioc 1.1 \includegraphics[width=0.5\linewidth]{plots/CR4plots/mt_met150_leadmuo_nj4.pdf}%
279     \includegraphics[width=0.5\linewidth]{plots/CR4plots/mt_met150_leadele_nj4.pdf}
280     \includegraphics[width=0.5\linewidth]{plots/CR4plots/mt_met200_leadmuo_nj4.pdf}%
281     \includegraphics[width=0.5\linewidth]{plots/CR4plots/mt_met200_leadele_nj4.pdf}
282     \caption{
283     Comparison of the \mt\ distribution in data vs. MC for events
284     with a leading muon (left) and leading electron (right)
285     satisfying the requirements of CR4. The \met\ requirements used are
286 vimartin 1.3 50 GeV (top), 200 GeV (middle) and 250 GeV (bottom).
287 claudioc 1.1 \label{fig:cr4mtrest}
288     }
289     \end{center}
290     \end{figure}
291    
292    
293     \clearpage