| 30 |
|
discriminant. This match is described in azimuthal and pseudorapidity planes and denoted as |
| 31 |
|
$\Delta\phi$ and $\Delta\eta$, respectively. |
| 32 |
|
|
| 33 |
+ |
\subsubsection{E/p-based variables} |
| 34 |
+ |
Electron should deposit all of its energy in the ECAL detector, thus the track momentum |
| 35 |
+ |
at the outer edge of tracker $p_{out}$ should be of the same order as an energy of the seed EM |
| 36 |
+ |
cluster $E_{seed}$. Jet is reconstructed combining information from CMS tracker and hadronic calomitere (HCAL). It interact with ECAL much less intensively and most of its energy, carried after tracker, is deposited in HCAL. Hence, $p_{out}$ and $E_{seed}$ differ significantly for the jets and can be used to discriminate them from electrons. |
| 37 |
+ |
We also considered an official version of this discriminant $E_{SC}/p_{in}$, where $E_{SC}$ is a SC energy, and $p_{in}$ is the initial momentum of a charged particle. |
| 38 |
+ |
|
| 39 |
|
\subsubsection{ECAL energy width} |
| 40 |
|
An electron brems extensively in CMS tracker, which results in a rather wide shower in azimuthal |
| 41 |
|
plane due to a strong CMS magnetic field. However, the width of a shower in pseudorapidity |
| 48 |
|
\sigma_\eta = \frac{1}{E_{SC}} \sqrt{\sum_{ECAL~SC~RecHits} E_i(\eta_i - \eta_{SC})^2}. |
| 49 |
|
\end{equation} |
| 50 |
|
|
| 45 |
– |
\subsubsection{E/p-based variables} |
| 46 |
– |
Electron should deposit all of its energy in the ECAL detector, thus the track momentum |
| 47 |
– |
at the outer edge of tracker $p_{out}$ should be of the same order as an energy of the seed EM |
| 48 |
– |
cluster $E_{seed}$. Jet is reconstructed combining information from CMS tracker and hadronic calomitere (HCAL). It interact with ECAL much less intensively and most of its energy, carried after tracker, is deposited in HCAL. Hence, $p_{out}$ and $E_{seed}$ differ significantly for the jets and can be used to discriminate them from electrons. |
| 49 |
– |
We also considered an official version of this discriminant $E_{SC}/p_{in}$, where $E_{SC}$ is a SC energy, and $p_{in}$ is the initial momentum of a charged particle. |
| 50 |
– |
|
| 51 |
|
\subsubsection{H/E variables} |
| 52 |
|
One can form a powerful discriminant by using the HCAL and ECAL energies associated |
| 53 |
|
with an electron candidate, as electrons tend to deposit very little or no energy in HCAL, |
| 54 |
|
while jets produce a wide energy deposition in the HCAL. An variable used in official |
| 55 |
|
``Robust" as well as ``Loose" and ``Tight" criteria is the ratio of HCAL and ECAL energies: $H/E$. |
| 56 |
|
It peaks around 0 for electrons and can be quite large for em-jets. We form a variable that also |
| 57 |
< |
takes into account the width of the HCAL energy deposition by making a ratio of the energy deposited |
| 57 |
> |
takes into account the width of the ECAL energy deposition by making a ratio of the energy deposited |
| 58 |
|
in HCAL and ECAL in the cone of $\Delta R < 0.3$ which is not included in the SC, normalized |
| 59 |
|
to the SC energy as follows |
| 60 |
|
|
| 128 |
|
are used at the first dictriminants. The disctribution of these variables are shown on figures ~\ref{fig:DeltaEta} |
| 129 |
|
and ~\ref{fig:DeltaPhi} respectively. |
| 130 |
|
|
| 131 |
< |
\begin{figure}[tb] |
| 131 |
> |
\begin{figure}[!tb] |
| 132 |
|
\begin{center} |
| 133 |
|
\includegraphics[width=16cm]{Figs/deltaEta.eps} |
| 134 |
|
\vspace{-10mm} |
| 138 |
|
\end{figure} |
| 139 |
|
|
| 140 |
|
|
| 141 |
< |
\begin{figure}[tb] |
| 141 |
> |
\begin{figure}[!tb] |
| 142 |
|
\begin{center} |
| 143 |
|
\includegraphics[width=16cm]{Figs/deltaPhi.eps} |
| 144 |
|
\vspace{-10mm} |
| 152 |
|
two ways of parametrization described in section 4.1.2 and checked their power on rejecting em-jets lookeing |
| 153 |
|
at background efficinecy $v.s.$ signal efficinecy.This comparison is presented figure ~\ref{fig:SigmaEE_vs_EtaWidth}. |
| 154 |
|
|
| 155 |
< |
\begin{figure}[tb] |
| 155 |
> |
\begin{figure}[!tb] |
| 156 |
|
\begin{center} |
| 157 |
|
\includegraphics[width=16cm]{Figs/Eff_EtaWidth_SigmaEtaEta.eps} |
| 158 |
|
\vspace{-10mm} |
| 163 |
|
|
| 164 |
|
As it can be seen $\sigma_{\eta\eta}$ variable is more powerfull in Barrel allowing to reject \~ 70\% of em-jet with only couple of \% loss of signal, while in endcap the performance of these two variables are more comparable. This result leads us to keep $\sigma_{\eta\eta}$ in our selection. Distribution of $\sigma_{\eta\eta}$ is presented on figure ~\ref{fig:SigmaEtaEta}. |
| 165 |
|
|
| 166 |
< |
\begin{figure}[tb] |
| 166 |
> |
\begin{figure}[!tb] |
| 167 |
|
\begin{center} |
| 168 |
|
\includegraphics[width=16cm]{Figs/Eff_EtaWidth_SigmaEtaEta.eps} |
| 169 |
|
\vspace{-10mm} |
| 181 |
|
is shown in figure ~\ref{fig:EseedOPout_vs_EoP}. |
| 182 |
|
|
| 183 |
|
|
| 184 |
< |
\begin{figure}[tb] |
| 184 |
> |
\begin{figure}[!tb] |
| 185 |
|
\begin{center} |
| 186 |
|
\includegraphics[width=16cm]{Figs/Eff_EoP_EseedoPout.eps} |
| 187 |
|
\vspace{-10mm} |
| 194 |
|
$E_{seed}/p_{out}$ is included as another criterion in ``Simple Loose'' selection. Its distribution both in barrel |
| 195 |
|
and endcap is shown on figure ~\ref{fig:EseedOPout} |
| 196 |
|
|
| 197 |
< |
\begin{figure}[tb] |
| 197 |
> |
\begin{figure}[!tb] |
| 198 |
|
\begin{center} |
| 199 |
|
\includegraphics[width=16cm]{Figs/EseedPout.eps} |
| 200 |
|
\vspace{-10mm} |
| 209 |
|
us better identify real electrons from em-jets, figure ~\ref{fig:TrkIso_no_vs_norm} |
| 210 |
|
|
| 211 |
|
|
| 212 |
< |
\begin{figure}[tb] |
| 212 |
> |
\begin{figure}[!tb] |
| 213 |
|
\begin{center} |
| 214 |
|
\includegraphics[width=16cm]{Figs/Eff_trkISoNonNorm_trkIsoNorm.eps} |
| 215 |
|
\vspace{-10mm} |
| 231 |
|
in selecting real electrons than $H/E$. Thus we keep $Iso_{EmHad}$ as the additional criterion for ``Simple Tight'' |
| 232 |
|
selection. Its istribution is presented on figure ~\ref{fig:EmHadIso} |
| 233 |
|
|
| 234 |
< |
\begin{figure}[tb] |
| 234 |
> |
\begin{figure}[!tb] |
| 235 |
|
\begin{center} |
| 236 |
|
\includegraphics[width=16cm]{Figs/EmHadIso.eps} |
| 237 |
|
\vspace{-10mm} |
