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nam
2014-10-30 18:56:57 +09:00
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37
thesis/chapters/chap3_comet.tex
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@@ -642,7 +642,7 @@ CyDet.
\end{figure}
\subsubsection{CDC configuration}
\label{ssub:CDC configuration}
\label{ssub:CDC_configuration}
The CDC is the main tracking detector that provides information for
reconstruction of charged particle tracks and measuring their momenta. The key
parameters for the CDC are listed in the
@@ -725,30 +725,33 @@ of protons emitted after muon capture in aluminium. In the design of the COMET
Phase-I, we use a conservative estimation of the rate of protons from energy
spectrum of charged particles emitted from muon capture in
$^{28}$Si~\cite{SobottkaWills.1968}. The baseline design for the proton
absorber is 1.0~\si{\milli\meter}-thick CFRP, making the total thickness
of material before the sensitive region is \SI{1.5}{\mm} in CFRP. In this
configuration, the inner wall and the proton absorber deteriorate the momentum
resolution of the reconstructed track to 195~\si{\kilo\electronvolt\per\cc}.
absorber is 0.5~\si{\milli\meter}-thick CFRP, making the total thickness
of material before the sensitive region is \SI{1.0}{\mm} in CFRP. In this
configuration, the inner wall and the proton absorber contribute a spread of
\SI{167}{\keV\per\cc} to the momentum of a \mueconv signal electron. This
figure is a little below the spread cause by multiple scatterings on the
chamber gas at \SI{197}{\keV\per\cc}.
The impact of the proton absorber on the CDC's hit rate and momentum
resolution is summarised in \cref{tab:comet_absorber_impact}.
\begin{table}[htb]
\begin{center}
\begin{tabular}{@{}ccc@{}}
\begin{tabular}{@{}cccc@{}}
\toprule
\textbf{Absorber }& \textbf{Proton }& \textbf{Momentum }\\
\textbf{thickness }& \textbf{hit rate }& \textbf{resolution }\\
(\si{\um}) & (\si{\kHz}) & (\si{\keV\per\cc}) \\
\textbf{Absorber }& \textbf{Total CFRP }&\textbf{Proton }&
\textbf{$\Delta p$}\\
\textbf{thickness }& \textbf{thickness }&\textbf{hit rate }& \\
(\si{\mm}) &(\si{\mm}) & (\si{\kHz}) & (\si{\keV\per\cc}) \\
\midrule
0 & 130 & 131 \\
0.5 & 34 & 167 \\
1.0 & 11 & 195 \\
1.5 & 6 & 252 \\
0 & 0.5 & 130 & 131 \\
0.5 & 1.0 & 34 & 167 \\
1.0 & 1.5 & 11 & 195 \\
1.5 & 2.0 & 6 & 252 \\
\bottomrule
\end{tabular}
\end{center}
\caption{Hit rates and contributions to momentum resolution of the proton
absorber and inner wall of the CDC. The intrinsic momentum resolution due
to multiple scattering is \SI{197}{\keV\per\cc}.}
\caption{Hit rates and contributions to momentum spread of the proton
absorber and inner wall of the CDC. The resolutions are calculated for
mono-energetic electrons of \SI{104.96}{\MeV\per\cc}.}
\label{tab:comet_absorber_impact}
\end{table}
@@ -758,7 +761,7 @@ emission rate and energy spectrum is being carried out at PSI. This experiment
is described in detail in next chapters.
It should be noted that the proton hit rate is not a problem for the COMET
Phase-II where the additional electron transport solenoid will removed all
Phase-II where the additional electron transport solenoid would removed all
protons emitted.
% subsection detectors_for_mueconv_search_in_the_phase_i (end)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%