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\begin{document}

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\newcommand{\don}{\ensuremath{d_{\textsc{ON}}}}
\newcommand{\doff}{\ensuremath{d_{\textsc{OFF}}}}
\newcommand{\dsoma}{\ensuremath{d_{\textsc{SOMA}}} \xspace}
\newcommand{\um}{\ensuremath{\mu \text{m}}\xspace}
\newcommand{\dmin}{d$_{\textup{min}}$\xspace}

%\title{Status report: \\Development of a time projection chamber for the $\mu^+
%\rightarrow e^+e^+e^-$ experiment}
\title{A study of a new experiment to search for the $\mu^+
\rightarrow e^+e^+e^-$ decay}
%%\subtitle{The poster subtitle here}
\author{Tran Hoai Nam}
\address{Department of Physics, Graduate School of Science, Osaka University}

\makeposter

\section{Introduction}

{\Large 
\begin{itemize}
	\item New physics beyond the Standard Model: the $\mu^+ \rightarrow e^+e^+e^-$
		decay is a forbidden process. 
	\item Current status of the experiment: upper limit of the branching ratio is 
		$1.0\times10^{-12}$ \cite{belgrade}.
\end{itemize}
}
%It is known that in the current theoretical framework of particle physics, the
%Standard Model, lepton flavor is conserved. Charged lepton flavor violation
%(cFLV) processes that violates lepton flavor number are not allowed. However,
%extensions of the Standard Model predict that cFLV might occur at the rate that
%future experiments can reach\cite{kunorev}. Experimental observation of such
%processes would provide a clear evidence for new physics beyond the Standard
%Model.  
%
%In this study, I am planning to develop a central tracking detector for an
%experimental search for a 
%neutrino-less decay of muon, the $\mu^+ \rightarrow e^+e^+e^-$ decay, at the
%MuSIC facility, Research Center for Nuclear Physics, Osaka University. In
%the past, many experiments have been carried out in attempt to find evidence
%for such a process. Among them, the most recent experiment was done at Paul
%Sherrer Institute (PSI) in Switzerland. From the experiment, the upper limit (at
%confidence level of 90\%) for the branching ratio $\mu^+ \rightarrow
%e^+e^+e^-$ normalized to the normal muon decay of $1.0\times10^{-12}$ is
%reported\cite{belgrade}.
%In order to carry out the search for 
%Purpose of this research is to develop a central tracking detector for an
%experimental 
%search for the $\mu^+ \rightarrow e^+e^+e^-$ decay at the MuSIC, Research Center
%for Nuclear Physics (RCNP), Osaka University. The $\mu^+ \rightarrow e^+e^+e^-$
%decay is a charged lepton flavor
%violation (cFLV) process, which is forbidden process in the Standard Model.
%However, various extensions of the Standard Model predict that cFLV might occur
%at the rate that future experiments can reach. Current experimental upper limit
%(at confidence level of 90\%) for the branching ratio $\mu^+ \rightarrow
%e^+e^+e^-$ is $1.0 × 10−12$
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Methods}
{\Large
In order to carry out the experiment, two important items
are needed: a high-intensity muon beam; and a good tracking detector. 
}

\subsection{The MuSIC facility}
\begin{center}
 \includegraphics[width=27cm]{figs/music.eps}
 \caption{Schematic view of the MuSIC}
 \label{fig:schememusic}
\end{center}
%The goal of this experiment is to achieve a sensitivity of $1.0\times10^{-14}$,
%which means two orders of magnitude improvement from the current limit. To carry
%out a search for the  $\mu^+ \rightarrow e^+e^+e^| $ process at such a
%sensitivity, a highly intense muon source is needed because the number of muons
%that would be usable for an experiment will determine the sensitivity. This high
%intensity source will be available at the MuSIC (Muon Science Innovative
%Channel), a newly installed beam line at RCNP (Research Center for Nuclear
%Physics), Osaka University. 
{\Large
\begin{itemize}
	\item MuSIC (\textbf{Mu}on \textbf{S}cience \textbf{I}nnovative
		\textbf{C}hannel): a
		newly installed beam line at RCNP, Osaka University.
	\item The world most intense muon beam: $10^9$ muons/sec with 1 $\mu$A proton
		beam current (400 MeV in energy)
	\item Purpose: particle physics, nuclear physics, material science, \ldots
	\item DC beam: important characteristic for the $\mu^+ \rightarrow e^+e^+e^- $
		experiment, because it reduces accidental background.
\end{itemize}
}

\columnbreak
\subsection{The time projection chamber (TPC)} 
{\Large
\begin{itemize}
	\item Use for tracking charged particles ($e^- $ and $e^+$) which are products
		of the $\mu^+ \rightarrow e^+e^+e^- $ event. The event signatures are: a)
		$\Sigma p = 0$; b) $\Sigma E = m_\mu$; c) same vertex; d) same time.
	\item GEM-TPC (figure below) is a good candidate, because:
		\begin{itemize}
			\item Event vertex can be reconstructed,
			\item Can work at high count rate while maintaining high resolution
				\cite{fabbi32}
		\end{itemize}
%	\item Advantages of GEM-TPC:
\end{itemize}
}

\begin{center}
 \includegraphics[width=25cm]{figs/gemtpc.eps}
 \caption{Illustration of a GEM-TPC (a); and GEM structure (b).}
 \label{fig:gemtpc}
\end{center}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Plan\& Status} 
\subsection{Plan} 
{\Large
\noindent \textbf{The first step is simulation study:}
\begin{itemize} 
%		\setlength{\itemsep}{0pt} 
	\item Event generator
	\item Geant4 simulation for the MuSIC beam line 
	\item Transportation of charged particles in the detector
%		by Garfield simulation toolkit(\url{http://garfield.web.cern.ch/garfield/})

\textcolor{red}{$\rightarrow$} results will be used to design a prototype GEM-TPC.
\end{itemize} 
%\vspace{-0.3cm}
\noindent \textbf{Next step is experiments:}
\begin{itemize}
	\item A prototype TPC (20 cm $\times$ 10 cm) will be constructed,
	\item Experiments to test its performance and optimize
\end{itemize}
}

\columnbreak

\subsection{Status}
{\Large
Currently, I have finished part of simulation study, that includes:
\begin{itemize}
	\item An event generator to simulate $\mu^+ \rightarrow e^+e^+e^-$ events
		based on different models. From this simulation, acceptance of the detector
		can be predicted:
		\begin{center}
		 \includegraphics[width=20cm]{figs/acceptance.eps}
		 \caption{Acceptance of the detector as a function of the momentum cut}
		 \label{fig:acceptance}
		\end{center}
	\item Simple model of the TPC to register the $\mu^+ \rightarrow e^+e^+e^-$
		events, and an event reconstruction program has been developed:
		\begin{center}
		 \includegraphics[width=20cm]{figs/tpc.eps}
		 \caption{Simple model of the TPC}
		 \label{fig:model}
		\end{center}
\end{itemize}

Also, the prototype construction is subject to be funded.
}
%\centerline{\includegraphics[width=\linewidth]{figs/w81s_4poster.ps}}
%\centerline{ \textbf{Figure 5}: \textit{Results for field W81s (same format as
%Fig.~4).}}
%
%\vspace*{20mm}
%%% Try to align numbers; not perfect but works.
%\def\0{\hbox{\phantom{\footnotesize\rm 1}}}%.  \def\tabcolsep{4mm}
%\begin{center} \begin{tabular}{cccccc} \hline field &    \# ON &  \# OFF & \don
%	& \doff       & soma \\
%    %%          & (\#)  & (\#) & (\um)      &  (\um)      & (\um) \\
%		\hline W81s  &    65 &   70 & $116 \pm 20$ \um  & $130  \pm 25$ \um & \09
%		\um\\ M623  &    74 &   82 & $100 \pm 13$ \um  & $\090 \pm 15$ \um & 15 \um
%		\\ \hline \end{tabular} \end{center}
%
%\vspace*{5mm}
%
%\textbf{Table~1}: \textit{Best-fit parameters of the \dmin model to the two
%datasets.  \don\  and \doff: mean $\pm$ s.d. of homotypic exclusion zones; soma:
%diameter of heterotypic exclusion zone.}
%

\vspace*{-1cm}

\begin{thebibliography}{99}
		\setlength{\itemsep}{-2mm}
%	\bibitem{kunorev}Y. Kuno and Y. Okada, Review of Modern Physics
%		(2001) 73 151-202
	\bibitem{belgrade}U. Belgrade et al., Nuclear Physics B (1988) 299
		1-6
	\bibitem{fabbi32}L. Fabbietti et al., Nuclear Instruments and Methods in
		Physics Research A 628 (2011) 204-208
%	\bibitem{music}The MuSIC collaboration, The MuSIC Project under The
%		Center of Excellence of Sub Atomic Physics (not published)
\end{thebibliography}

\end{document}

% LocalWords:  RGCs
