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\newcommand{\mueg}{$\mu^{+} \rightarrow e^{+}\gamma$~}
\newcommand{\meee}{$\mu \rightarrow eee$~}
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\newcommand{\muecaz}{$\mu^{-} + N(A,Z) \rightarrow e^{-} + N(A,Z)$~}


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%{\large\bfseries The COMET Experiment and its Background Study}
{\large\bfseries Status of the COMET Experiment at J-PARC}

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\underline{Nam Hoai Tran}, on behalf of the COMET Collaboration 

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{\small\itshape
Department of Physics, Graduate School of Science, \\
Osaka University, Osaka
560-0043, Japan}\\

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{\small nam@kuno-g.phys.sci.osaka-u.ac.jp}

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COMET [1] is an experiment that aims to search for a charged lepton flavor violation
(CLFV) process, the muon-to-electron conversion in the presence of a nucleus,
\muec. The process is forbidden in the Standard Model (SM), however is
predicted to occur in various extensions of SM, such as . Current experimental
upper limit of the branching ratio is $BR(\mu^{-} + Au \rightarrow e^{-} + Au)
< 7 \times 10^{-13}$, set by the SINDRUM II experiment [2].

Using the J-PARC proton beam and the pion capture by
a solenoidal field, COMET will have a single event sensitivity  10,000 times
better than the current limit. The COMET collaboration has taken a phased
approach in which the first phase, COMET Phase-I [3], starts in 2013 and
initial data taking in around 2016. This paper provides some highlights among
ongoing R\&D activities.

%Charged lepton flavor violation (CLFV) has attracted much attention from
%experimentalists and theorists in particle physics. The CLFV rates are
%predicted to be in the order of of $O(10^{-54})$ in the Standard Model (SM).
%Therefore, any experimental observations of CLFV would be an unambiguous signal
%of new physics beyond the SM. COMET [1] is an experiment
%that aims to search for a CLFV process of muon-to-electron conversion in the
%presence of a nucleus, \muec. 
%Using the J-PARC proton beam and the pion capture by
%a solenoidal field, COMET expects to have a sensitivity a factor of 10,000
%times that of the current limit. The COMET experiment has taken a phased
%approach [2] in which the COMET Phase-I (first phase) will start its
%construction in 2013 and initial data taking in around 2016. 

%The COMET Phase-I will be subjected to significant backgrounds from the
%products of the nuclear muon capture process. However, experimental data on
%this matter is insufficient. As so, precise measurements of the products,
%including protons, neutrons and photons, are required for the design and
%optimization of the experiment. Detailed of these measurements will be
%presented.

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%%% LIST OF REFERENCES

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~[1] Y.~Kuno {\it et al.} (COMET collaboration),  ``A Experimental
	Search for Lepton Flavor Violating \muec Conversion at Sensitivity of
	$10^{-16}$ with A Slow-Extracted Bunched Proton Beam'', J-PARC Proposal, 2007
	and J-PARC Conceptual Design Report, 2009.\\

~[2] W.~Bertl {\it et al.} (SINDRUM-II collaboration),  ``A search for $\mu
- e$ conversion in muonic gold'', The European Physical Journal C 47 (2006)
337-346.\\

~[3] Y.~Kuno {\it et al.} (COMET collaboration), ``Letter of
	Intent of Phase-I for the COMET Experiment at J-PARC'', unpublished, March
	2012. 

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