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18
thesis/chapters/chap2_mu_e_conv.tex
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@@ -271,11 +271,11 @@ experimental limits on these two decay modes are set respectively by the MEG
experiment~\cite{Adam.etal.2013} and the SINDRUM-II experiment~\cite{Adam.etal.2013} and the SINDRUM-II
experiment~\cite{Bertl.etal.2006}: experiment~\cite{Bertl.etal.2006}:
\begin{equation} \begin{equation}
\mathcal{B}(\mu^+ \rightarrow e^+ \gamma) < 5.7 \times 10^{-13}\, \mathcal{B}(\mu^+ \rightarrow e^+ \gamma) < 5.7 \times 10^{-13}\,,
\end{equation} \end{equation}
and: and:
\begin{equation} \begin{equation}
\mathcal{B} (\mu^- + Au \rightarrow e^- +Au) < 7\times 10^{-13}\. \mathcal{B} (\mu^- + Au \rightarrow e^- +Au) < 7\times 10^{-13}\,.
\end{equation} \end{equation}
%\hl{TODO: mueg and muec relations, Lagrangian \ldots} %\hl{TODO: mueg and muec relations, Lagrangian \ldots}
@@ -307,14 +307,13 @@ In the context of physics beyond the SM, the exotic process of \mueconv where
a muon decays to an electron without neutrinos is also a muon decays to an electron without neutrinos is also
expected, but has never been observed: expected, but has never been observed:
\begin{equation} \begin{equation}
\mu^{-} + N(A,Z) \rightarrow e^{-} + N(A,Z)\. \mu^{-} + N(A,Z) \rightarrow e^{-} + N(A,Z)\,.
\end{equation} \end{equation}
The emitted electron in this decay The emitted electron in this decay mode, the \mueconv electron, is
mode , the \mueconv electron, is mono-energetic at an energy far above the mono-energetic at an energy far above the endpoint
endpoint
of the Michel spectrum (52.8 MeV): of the Michel spectrum (52.8 MeV):
\begin{equation} \begin{equation}
E_{\mu e} = m_\mu - E_b - \frac{E^2_\mu}{2m_N} E_{\mu e} = m_\mu - E_b - \frac{E^2_\mu}{2m_N}\,.
\end{equation} \end{equation}
where $m_\mu$ is the muon mas; $E_b \simeq Z^2\alpha^2 m_\mu/2$ is the binding where $m_\mu$ is the muon mas; $E_b \simeq Z^2\alpha^2 m_\mu/2$ is the binding
energy of the muonic atom; and the last term is the nuclear recoil energy energy of the muonic atom; and the last term is the nuclear recoil energy
@@ -351,7 +350,10 @@ The mean lifetime $\tau = 1/\Gamma$, then:
\end{equation} \end{equation}
The mean lifetimes of free muons and muons in a material are well-known, The mean lifetimes of free muons and muons in a material are well-known,
therefore the number of captures can be inferred from the number of stops. For therefore the number of captures can be inferred from the number of stops. For
aluminium, $\frac{\Gamma_{\textrm{capture}}}{\Gamma_{\textrm{stop}}} = 0.609$ aluminium,
\begin{equation}
\frac{\Gamma_{\textrm{capture}}}{\Gamma_{\textrm{stop}}} = 0.609
\end{equation}
and the mean lifetime of stopped muons is 864 and the mean lifetime of stopped muons is 864
ns~\cite{SuzukiMeasday.etal.1987}. ns~\cite{SuzukiMeasday.etal.1987}.

286
thesis/chapters/chap3_comet.tex
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@@ -5,8 +5,8 @@
This chapter describes the new experimental search for \mueconv, namely COMET - This chapter describes the new experimental search for \mueconv, namely COMET -
(\textbf{CO}herent \textbf{M}uon to \textbf{E}lectron \textbf{T}ransition). The (\textbf{CO}herent \textbf{M}uon to \textbf{E}lectron \textbf{T}ransition). The
experiment will be carried out at the Japan Proton Accelerator Research Complex experiment will be carried out at the Japan Proton Accelerator Research Complex
(J-PARC), aims at a sensitivity of \sn{6}{-17} i.e. 10,000 times better than the (J-PARC), aims at a single event sensitivity of \num{6E-17}, i.e. 10,000 times
current best limit. better than the current best limit.
%At the Japan Proton Accelerator Research Complex (J-PARC), an experiment to %At the Japan Proton Accelerator Research Complex (J-PARC), an experiment to
%search for \muec~conversion, which is called %search for \muec~conversion, which is called
@@ -48,8 +48,9 @@ current best limit.
The searches for \mueconv has been ongoing for more than 50 years, started in The searches for \mueconv has been ongoing for more than 50 years, started in
1952 with cosmic rays~\cite{LagarriguePeyrou.1952} and then moved to 1952 with cosmic rays~\cite{LagarriguePeyrou.1952} and then moved to
accelerators. The list in the Table~\ref{tab:mueconv_history} is reproduced accelerators. The list of upper limits for \mueconv in
from a recent review of Bernstein and Cooper~\cite{BernsteinCooper.2013}. \cref{tab:mueconv_history} is reproduced from a recent review of Bernstein
and Cooper~\cite{BernsteinCooper.2013}.
\begin{table}[htb] \begin{table}[htb]
\begin{center} \begin{center}
\begin{tabular}{l l l c} \begin{tabular}{l l l c}
@@ -79,40 +80,43 @@ from a recent review of Bernstein and Cooper~\cite{BernsteinCooper.2013}.
\label{tab:mueconv_history} \label{tab:mueconv_history}
\end{table} \end{table}
The most recent experiments were the SINDRUM and SINDRUM-II at the Paul The latest experiments were the SINDRUM and SINDRUM-II at the Paul
Scherrer Institute (PSI), Switzerland. The SINDRUM-II measured the branching Scherrer Institute (PSI), Switzerland. The SINDRUM-II
(\cref{fig:sindrumII_setup}) measured the branching
ratio of \mueconv on a series of heavy targets: Ti, Pb and Au. The proton beam ratio of \mueconv on a series of heavy targets: Ti, Pb and Au. The proton beam
at PSI is a continuous wave beam, with a time structure of 0.3 ns bursts every at PSI is a continuous beam, with a time structure of 0.3 ns bursts every
19.75 \si{\nano\second}. An 8-\si{\milli\meter}-thick CH$_2$ degrader was used to reduce 19.75 \si{\nano\second}. An 8-\si{\milli\meter}-thick CH$_2$ degrader was used
the radiative pion capture and other prompt backgrounds. Cosmic backgrounds are to reduce the radiative pion capture and other prompt backgrounds. Cosmic
backgrounds are
rejected using a combination of rejected using a combination of
passive shielding, veto counters and reconstruction cuts. The momenta of muons passive shielding, veto counters and reconstruction cuts. The momenta of beam
were 52 \si{\mega\electronvolt\per\cc} and 53 \si{\mega\electronvolt\per\cc}, and the muons used in the experiment were \SI{52}{\MeV\per\cc} and
momentum spread was 2\%. \SI{53}{\MeV\per\cc}, and the momentum spread was 2\%.
\begin{figure}[htbp] \centering \begin{figure}[htbp] \centering
\includegraphics[width=0.85\textwidth]{figs/sindrumII_setup} \includegraphics[width=0.85\textwidth]{figs/sindrumII_setup}
\caption{SINDRUM-II set up} \caption{SINDRUM-II set up}
\label{fig:sindrumII_setup} \label{fig:sindrumII_setup}
\end{figure} \end{figure}
Electrons emitted from the target were tracked in a 0.33 T solenoid field. Electrons emitted from the target were tracked in a 0.33 T solenoidal magnetic
Detector system consisted of a superconducting solenoid, two plastic field. Detector system consisted of a superconducting solenoid, two plastic
scintillation hodoscopes, a plexiglass Cerenkov hodoscope, and two drift scintillation hodoscopes, a plexiglass Cerenkov hodoscope, and two drift
chambers. In the latest measurement, the SINDRUM-II collaboration have not chambers. In the latest measurement, the SINDRUM-II collaboration have not
found any conversion electron from captured muons in a gold target, hence set found any conversion electron from captured muons in a gold target, hence set
the upper limit for the upper limit for
the branching ratio of \mueconv in gold with 90 \% C.L. at \sn{7.0}{-13}. the branching ratio of \mueconv in gold with 90 \% C.L. at \num{7.0E-13}.
The reconstructed momenta of electrons around the signal region from SINDRUM-II The reconstructed momenta of electrons around the signal region from SINDRUM-II
is shown in the Figure~\ref{fig:sindrumII_result}. It can be seen that the muon is shown in \cref{fig:sindrumII_result}. It can be seen that the muon
decay in orbit background falls steeply near the endpoint as expected, but, the decay in orbit background falls steeply near the endpoint as expected, but, the
prompt background induced by pions still remains even after the cut in timing prompt background induced by pions still remains even after the cut in timing
and track angle. This indicates the problem of pion contamination is very and track angle. This indicates the problem of pion contamination is very
important in probing lower sensitivity. important in probing better sensitivity.
\begin{figure}[htbp] \begin{figure}[htbp]
\centering \centering
\includegraphics[width=0.55\textwidth]{figs/sindrumII_Au_result} \includegraphics[width=0.55\textwidth]{figs/sindrumII_Au_result}
\caption{SINDRUM-II result} \caption{SINDRUM-II results}
%TODO: explain top and bottom figure
\label{fig:sindrumII_result} \label{fig:sindrumII_result}
\end{figure} \end{figure}
% subsection experimental_history (end) % subsection experimental_history (end)
@@ -124,28 +128,30 @@ A new generation of \mueconv experiments have been proposed with scenarios to
overcome pion induced background in the SINDRUM-II. Lobashev and collaborators overcome pion induced background in the SINDRUM-II. Lobashev and collaborators
first suggested the basic idea for new \mueconv at the Moscow Muon Factory; first suggested the basic idea for new \mueconv at the Moscow Muon Factory;
this idea was used to develop the MECO experiment at Brookhaven National this idea was used to develop the MECO experiment at Brookhaven National
Laboratory. The MECO experiment was cancelled due to budget constraints. The two Laboratory. The MECO experiment was cancelled due to budget constraints. Two
modern experiments, COMET at J-PARC and Mu2e at Fermilab use the initial idea recent experiments, COMET at J-PARC and Mu2e at Fermilab, use the initial idea
with more upgrades and modifications. with more upgrades and modifications.
The basic ideas of the modern experiments are: The basic ideas of the two experiments are:
\begin{enumerate} \begin{enumerate}
\item Highly intense muon source: the total number of muons needed is of the \item Highly intense muon source: the total number of muons needed is of the
order of $10^{18}$ in order to achieve a sensitivity of $10^{-16}$. This order of $10^{18}$ in order to achieve a sensitivity of $10^{-16}$. This
can be done by producing more pions using a high power proton beam, and can be done by producing more pions using a high power proton beam, and
having a high efficiency pion collection system; having a high efficiency pion collection system;
\item Pulsed proton beam with an appropriate timing: the proton pulse should \item Pulsed proton beam: the proton pulse should
be short compares to the lifetime of muons in the stopping target material, be short compares to the lifetime of muons in the stopping target material,
and the period between pulses should be long enough for prompt backgrounds and the period between pulses should be long enough for prompt backgrounds
from pion to decay before beginning the measurement. It is also crucial from pion to decay before beginning the measurement. It is also crucial
that there is no proton leaks into the measuring interval; that there is no proton leaks into the measuring interval;
\item Curved solenoids for charge and momentum selection: at first, the curved \item Curved solenoids for charge and momentum selection: at first, the curved
solenoids remove the line of sight backgrounds. A charged particle travels solenoids remove the line of sight backgrounds. A charged particle travels
through a curved solenoidal field will have the centre of the helical through a curved solenoidal magnetic field has the centre of the helical
motion drifted up or down depends on the sign of the charge, and the motion drifted up or down with respect to the bending plane depends on the
magnitude of the drift is proportional to its momentum. By using this sign of the charge, and the magnitude of the drift is proportional to its
effect and placing suitable collimators, charge and momentum selection can momentum. By using this effect and placing suitable collimators, charge and
be made. momentum selection can be made. Details of the magnet system are described
in \cref{sub:pion_production_can_capture_solenoid} and
\cref{sub:pion_and_muon_transportation}.
\end{enumerate} \end{enumerate}
% subsection new_generation_of_mueconv_experiments (end) % subsection new_generation_of_mueconv_experiments (end)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -156,13 +162,14 @@ The basic ideas of the modern experiments are:
\section{Concepts of the COMET experiment} \section{Concepts of the COMET experiment}
\label{sec:concepts_of_the_comet_experiment} \label{sec:concepts_of_the_comet_experiment}
This section elaborates the design choices of the COMET to realise the basic This section elaborates the design choices of the COMET to realise the basic
ideas mentioned above. Figures and numbers, other than noted, are taken from ideas mentioned previously. Figures and numbers, other than noted, are taken
the COMET's documentations: from the COMET's documentations:
\begin{itemize} \begin{itemize}
%TODO citations %TODO citations
\item Conceptual design report for the COMET experiment~\cite{COMET.2009} \item Conceptual design report for the COMET experiment~\cite{COMET.2009},
\item Proposal Phase-I 2012 \item Experimental Proposal for Phase-I of the COMET Experiment at
\item TDR 2014 J-PARC~\cite{COMET.2012},
\item and COMET Phase-I Technical Design Report~\cite{COMET.2014}.
\end{itemize} \end{itemize}
@@ -172,30 +179,30 @@ A high power pulsed proton beam is of utmost importance to achieve the desired
sensitivity of the COMET experiment. A slow-extracted proton beam from sensitivity of the COMET experiment. A slow-extracted proton beam from
the J-PARC main ring (MR), which is designed to deliver \sn{3.6}{15} protons per the J-PARC main ring (MR), which is designed to deliver \sn{3.6}{15} protons per
cycle at a frequency of 0.45 Hz, will be used for the COMET experiment. The cycle at a frequency of 0.45 Hz, will be used for the COMET experiment. The
proton beam power of the current design is 8 GeV$\times$7 $\mu$A, or proton beam power of the current design is $\SI{8}{\GeV}\times \SI{7}{\uA}$, or
\sn{4.4}{13} protons/s. The beam energy 8 \si{\giga\electronvolt} helps to minimise \num{4.4E13} protons/s at \SI{8}{\GeV}. The beam energy was chosen to minimise
the production of antiprotons. the production of antiprotons which may introduce background events.
The proton pulse width is chosen to be 100 ns, and the pulse period to be The proton pulse width is chosen to be 100 ns, and the pulse period to be
$1 \sim 2 \textrm{ }\mu\textrm{s}$. This time structure is sufficient for the from \SIrange{1}{2}{\us}. This time structure is sufficient for the
search for \mueconv in an aluminium target where the lifetime of muons is 864 search for \mueconv in an aluminium target where the mean lifetime of negative
ns. A plan of accelerator operation to realise the scheme is shown in muons in muonic atoms is \SI{864}{\ns}. One possible plan of accelerator
the Figure~\ref{fig:comet_mr_4filled}, where 4 out of 9 MR buckets are filled. operation to realise the beam pulsing is shown in \cref{fig:comet_mr_4filled},
where 4 out of 9 MR buckets are filled.
As mentioned, it is very important that there is no stray proton arrives in the As mentioned, it is very important that there is no stray proton arrives in the
measuring period between two proton bunches. An extinction factor is defined as measuring period between two proton bunches. An extinction factor is defined as
the ratio between number of protons in between two pulses and the number of the ratio between number of protons in between two pulses and the number of
protons in the main pulse. In order to achieve the goal sensitivity of the protons in the main pulse. In order to achieve the goal sensitivity of the
COMET, an extinction factor of \sn{}{-9} is required. COMET, an extinction factor less than \num{E-9} is required.
Requirements for the proton beam are summarised in the Requirements for the proton beam are summarised in \cref{tab:comet_proton_beam}.
Table~\ref{tab:comet_proton_beam}.
\begin{figure}[htb] \begin{figure}[htb]
\centering \centering
\includegraphics[width=0.8\textwidth]{figs/comet_mr_4filled} \includegraphics[width=0.8\textwidth]{figs/comet_mr_4filled}
\caption{The COMET proton bunch structure in the RCS (rapid cycle \caption{The COMET proton bunch structure in the RCS (Rapid Cycling
synchrotron) and MR where 4 buckets Synchrotron) and MR where 4 buckets
are filled producing 100 \si{\nano\second} bunches separated by are filled producing 100 \si{\nano\second} bunches separated by
1.2~\si{\micro\second}.} 1.2~\si{\micro\second}.}
\label{fig:comet_mr_4filled} \label{fig:comet_mr_4filled}
@@ -234,7 +241,7 @@ pions, are preferred. It is known from other measurements that backward
scattered pions (with respect to proton beam direction) of high energy are scattered pions (with respect to proton beam direction) of high energy are
suppressed, and the yield of low energy pions in the backward direction is not suppressed, and the yield of low energy pions in the backward direction is not
too low compares to that of the forward direction (see too low compares to that of the forward direction (see
Figure~\ref{fig:pion_yield}). For these reasons, the COMET \cref{fig:pion_yield}). For these reasons, the COMET
decided to collect backward pions. decided to collect backward pions.
\begin{figure}[htb] \begin{figure}[htb]
\centering \centering
@@ -243,10 +250,9 @@ decided to collect backward pions.
target.} target.}
\label{fig:pion_yield} \label{fig:pion_yield}
\end{figure} \end{figure}
The pion capture system is composed of several superconducting solenoids: The pion capture system is composed of several superconducting solenoids:
capture solenoids and matching solenoids. The magnetic field distribution along capture solenoids and matching solenoids. The magnetic field distribution along
the beam axis of the COMET is shown in the Figure~\ref{fig:comet_Bfield}. The the beam axis of the COMET is shown in \cref{fig:comet_Bfield}. The
peak field of 5 T is created by the capture solenoid, and the matching peak field of 5 T is created by the capture solenoid, and the matching
solenoids provide a smooth transition from that peak field to the 3 T field in solenoids provide a smooth transition from that peak field to the 3 T field in
the pions/muons transportation region. The superconducting solenoids are the pions/muons transportation region. The superconducting solenoids are
@@ -258,6 +264,7 @@ will be installed inside the cryostat to reduce radiation heat load.
\caption{Magnetic field distribution along the COMET beam line.} \caption{Magnetic field distribution along the COMET beam line.}
\label{fig:comet_Bfield} \label{fig:comet_Bfield}
\end{figure} \end{figure}
%TODO full comet field
% subsection pion_production_can_capture_solenoid (end) % subsection pion_production_can_capture_solenoid (end)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -266,7 +273,7 @@ will be installed inside the cryostat to reduce radiation heat load.
Muons and pions are transported to the muon stopping target through a muon Muons and pions are transported to the muon stopping target through a muon
beam line, which includes several curved and straight superconducting solenoid beam line, which includes several curved and straight superconducting solenoid
magnets. A schematic layout of the muon beam line, include the capture and magnets. A schematic layout of the muon beam line, include the capture and
detector sections, is shown in Figure~\ref{fig:comet_beamline_layout}. detector sections, is shown in \cref{fig:comet_beamline_layout}.
\begin{figure}[htb] \begin{figure}[htb]
\centering \centering
\includegraphics[width=0.95\textwidth]{figs/comet_beamline_layout} \includegraphics[width=0.95\textwidth]{figs/comet_beamline_layout}
@@ -292,7 +299,7 @@ of the drift is given by:
&= \frac{1}{qB} \frac{s}{R} \frac{p}{2} &= \frac{1}{qB} \frac{s}{R} \frac{p}{2}
\left( \textrm{cos}\theta + \frac{1}{\textrm{cos}\theta} \right)\\ \left( \textrm{cos}\theta + \frac{1}{\textrm{cos}\theta} \right)\\
&= \frac{1}{qB} \theta_{bend} \frac{p}{2} &= \frac{1}{qB} \theta_{bend} \frac{p}{2}
\left( \textrm{cos}\theta + \frac{1}{\textrm{cos}\theta} \right) \left( \textrm{cos}\theta + \frac{1}{\textrm{cos}\theta} \right)\,,
\end{align} \end{align}
where $q$ is the electric charge of the particle; $B$ is the magnetic field at where $q$ is the electric charge of the particle; $B$ is the magnetic field at
the axis; $s$ and $R$ are the path length and the radius of the curvature; $p$, the axis; $s$ and $R$ are the path length and the radius of the curvature; $p$,
@@ -312,7 +319,7 @@ produced by additional coils winded around the solenoid coils. The magnitude of
the compensating field is: the compensating field is:
\begin{equation} \begin{equation}
B_{\textrm{comp}} = \frac{1}{qR} \frac{p_0}{2} B_{\textrm{comp}} = \frac{1}{qR} \frac{p_0}{2}
\left( \textrm{cos}\theta_0 + \frac{1}{\textrm{cos}\theta_0} \right) \left( \textrm{cos}\theta_0 + \frac{1}{\textrm{cos}\theta_0} \right)\,,
\end{equation} \end{equation}
where the trajectories of charged particles with momentum $p_0$ and pitch angle where the trajectories of charged particles with momentum $p_0$ and pitch angle
$\theta_0$ are corrected to be on-axis. An average dipole field of 0.03 T is $\theta_0$ are corrected to be on-axis. An average dipole field of 0.03 T is
@@ -321,23 +328,42 @@ needed to select 40 MeV/$c$ muons as required by the COMET design.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\subsection{Muon stopping target} \subsection{Muon stopping target}
\label{sub:muon_stopping_target} \label{sub:muon_stopping_target}
Muon stopping target is place at 180\si{\degree}~bending after the pion production Muon stopping target is place at 180\si{\degree}~bending after the pion
target (Figure~\ref{fig:comet_beamline_layout}) in its own solenoid. The target production target (\cref{fig:comet_beamline_layout}) in its own solenoid. The
target
is designed to maximise the muon stopping efficiency and minimise the energy is designed to maximise the muon stopping efficiency and minimise the energy
loss of signal electrons. loss of signal electrons.
%\hl{TODO: Target choice: separation, product, lifetime, energy loss\ldots} %\hl{TODO: Target choice: separation, product, lifetime, energy loss\ldots}
It is calculated that the branching ratio of \mueconv increases with atomic It is calculated that the branching ratio of \mueconv increases with atomic
number $Z$, and plateaus above $Z \simeq 30$, then decreases as $Z>60$. The number $Z$, and plateaus above $Z \simeq 30$, then decreases as $Z>60$ (see
lifetime of muons inside a material decreases quickly as $Z$ increases. \cref{fig:comet_mueconv_RateVsZ}). Although the sensitivity is better for
Tracking wise, lower $Z$ material provides better reconstructed momentum higher $Z$ material, the acceptance of the measurement time window decreases
resolution. Therefore, light material is preferable as muon stopping target. quickly because the average lifetime of negative muons inside a material
decreases as $Z^{-4}$.
%Tracking wise, lower $Z$ material provides better
%reconstructed momentum
%resolution.
Therefore, light material is preferable as muon stopping target.
\begin{figure}[hbp]
\centering
\includegraphics[width=0.60\textwidth]{figs/comet_mueconv_RateVsZ}
\caption{Target dependence of the \mueconv rate in different models
calculated by Cirigliano and colleagues~\cite{CiriglianoKitano.etal.2009}.
The conversion rates are normalised to the rate in aluminium. Four models
were considered and noted with letters: D for dipole-interaction-dominated
model, V for vector and S for scalar interactions. The three vertical lines
from left to right correspond to $Z=13$(Al), $Z=22$(Ti), and $Z=82$(Pb)l
respectively.}
\label{fig:comet_mueconv_RateVsZ}
\end{figure}
The first choice for the muon stopping target material in the COMET is The first choice for the muon stopping target material in the COMET is
aluminium. A titanium target is also considered. Configuration of the target is aluminium. A titanium target is also considered in the future. Configuration of
shown in the Table~\ref{tab:comet_al_target}. Monte Carlo studies with this the target is shown in \cref{tab:comet_al_target}. Monte Carlo studies with
this
design showed that net stopping efficiency is 0.29, and average energy loss design showed that net stopping efficiency is 0.29, and average energy loss
of signal electrons is about 400 \si{\kilo\electronvolt}. of signal electrons is about \SI{400}{\keV}.
\begin{table}[htb] \begin{table}[htb]
\begin{center} \begin{center}
\begin{tabular}{l l} \begin{tabular}{l l}
@@ -358,7 +384,7 @@ of signal electrons is about 400 \si{\kilo\electronvolt}.
\end{table} \end{table}
A graded magnetic field (reduces from 3 T to 1 T) is produced at the A graded magnetic field (reduces from 3 T to 1 T) is produced at the
location of the stopping target (see Figure~\ref{fig:comet_target_Bfield}) to location of the stopping target (see \cref{fig:comet_target_Bfield}) to
maximise the acceptance for \mueconv signals, since electrons emitted in the maximise the acceptance for \mueconv signals, since electrons emitted in the
backward backward
direction would be reflected due to magnetic mirroring. The graded field also direction would be reflected due to magnetic mirroring. The graded field also
@@ -375,36 +401,36 @@ transport section.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\subsection{Electron transportation beam line} \subsection{Electron transportation beam line}
\label{sub:electron_transportation_beam_line} \label{sub:electron_transportation_beam_line}
The 180\si{\degree}~bending electron transport solenoids help remove line-of-sight The \ang{180} bending electron transport solenoids help remove line-of-sight
between the target and the detector system. It works similarly to the muon between the target and the detector system. It works similarly to the muon
transportation section, but is tuned differently to accept electrons of about transportation section, but is tuned differently to accept electrons of about
105~\si{\mega\electronvolt\per\cc}. A compensation field of 0.17 T along the \SI{105}{\MeV\per\cc}. A compensation field of \SI{0.17}{\tesla} along the
vertical direction will be applied. Electrons with momentum less than 80 vertical direction will be applied. Electrons with momentum less than
\si{\mega\electronvolt\per\cc} are blocked at the exit of this section by \SI{80}{\MeV\per\cc} are blocked at the exit of this section by
a collimator to reduce DIO electrons rate. The net acceptance of signals of a collimator to reduce DIO electrons rate. The net acceptance of signals of
\mueconv is about 0.32, and the detector hit rate will be in the order of \mueconv is about 0.32, and the detector hit rate will be in the order of
1~\si{\kilo\hertz}~for \sn{}{11} stopped muons\si{\per\second}. \SI{1}{\kHz} for a muon stopping rate of \SI{E11}{\Hz}.
% subsection electron_transportation_beam_line (end) % subsection electron_transportation_beam_line (end)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\subsection{Electron detectors} \subsection{Electron detectors}
\label{sub:electron_detectors} \label{sub:electron_detectors}
The \mueconv signal electrons is measured by an electron detector system, which The \mueconv signal electrons is measured by an electron detector system, which
consists of straw-tube trackers and an electromagnetic calorimeter - shown in consists of straw-tube trackers and an electromagnetic calorimeter - shown in
Figure~\ref{fig:comet_detector_system}. The \cref{fig:comet_detector_system}. The
requirements for the detector system is to distinguish electrons from other requirements for the detector system is to distinguish electrons from other
particles, and measure their momenta, energy and timings. The whole detector particles, and measure their momenta, energy and timings. The whole detector
system is in a uniform solenoidal magnetic field under vacuum. Passive and system is in a uniform solenoidal magnetic field under vacuum. Passive and
active shielding against cosmic rays is considered. active shielding against cosmic rays is considered.
The tracking detector has to provide a momentum resolution less than The tracking detector has to provide a momentum resolution less than
%%TODO 350 or 150?
350~\si{\kilo\electronvolt\per\cc} in order to achieve a sensitivity of 350~\si{\kilo\electronvolt\per\cc} in order to achieve a sensitivity of
\sn{3}{-17}. There are five stations of straw-tube gas chambers, each provides \sn{3}{-17}. There are five stations of straw-tube gas chambers, each provides
two two dimensional information. Each straw tube is 5~\si{\milli\meter} in diameter
dimensional information. Each straw tube is 5~\si{\milli\meter} in diameter and has and has a 25-\si{\micro\meter}-thick wall. According to a GEANT4 Monte Carlo
a 25~\si{\micro\meter}-thick wall. According to a GEANT4 Monte Carlo simulation, simulation, a position resolution of 250~\si{\micro\meter} can be obtained,
a position resolution of 250~\si{\micro\meter} can be obtained, which is enough for which is enough for 350~\si{\kilo\electronvolt\per\cc} momentum resolution. The
350~\si{\kilo\electronvolt\per\cc} momentum resolution. The DIO background of 0.15 DIO background of 0.15 events is expected.
events is estimated.
The electromagnetic calorimeter serves three purposes: a) to measure electrons The electromagnetic calorimeter serves three purposes: a) to measure electrons
energy with high energy resolution; b) to provide timing information and energy with high energy resolution; b) to provide timing information and
@@ -427,7 +453,7 @@ The requirements for \mueconv signals are:
muons decay in flight; muons decay in flight;
\item timing wise, conversion electrons should arrive in the time window of \item timing wise, conversion electrons should arrive in the time window of
detection which is about 700~\si{\nano\second}~after each proton pulses detection which is about 700~\si{\nano\second}~after each proton pulses
(Figure~\ref{fig:comet_meas_timing}). The acceptance in this detection (\cref{fig:comet_meas_timing}). The acceptance in this detection
window is about 0.39 for aluminium. window is about 0.39 for aluminium.
\end{itemize} \end{itemize}
@@ -472,7 +498,7 @@ Potential backgrounds for the COMET are:
\item Accidental background from cosmic rays \item Accidental background from cosmic rays
\end{enumerate} \end{enumerate}
The expected background rates for the COMET at an SES of The expected background rates for the COMET at an SES of
\sn{3}{-17} is summarised in Table~\ref{tab:comet_background_estimation}. \sn{3}{-17} is summarised in \cref{tab:comet_background_estimation}.
\begin{table}[htb] \begin{table}[htb]
\begin{center} \begin{center}
%\begin{tabular}{l l} %\begin{tabular}{l l}
@@ -516,11 +542,12 @@ are believed to greatly reduce potential backgrounds, by several orders of
magnitude, for the \mueconv search. That also means that backgrounds are being magnitude, for the \mueconv search. That also means that backgrounds are being
extrapolated over four orders of magnitude from existing data. In order to extrapolated over four orders of magnitude from existing data. In order to
obtain data-driven estimates of backgrounds, and inform the detailed design for obtain data-driven estimates of backgrounds, and inform the detailed design for
the ultimate COMET experiment, and initial phase is desirable. Also, the 5-year the ultimate COMET experiment, a staged approach is desirable. Also, the
mid-term plan from 2013 of J-PARC includes the construction of the COMET beam KEK/J-PARC 5-year mid-term plan from 2013 includes the construction
line. For these reasons, the COMET collaboration considers a staged approach of the COMET beam line. For these reasons, the COMET collaboration considers
with the first stage, so called COMET Phase-I, with a shorter muon to carry out the experiment in two stages. The first stage, so called COMET
transportation solenoid, up to the first 90\si{\degree}. Phase-I, with a shorter muon transportation solenoid, up to the first
90\si{\degree}.
%\begin{wrapfigure}{r}{0.5\textwidth} %\begin{wrapfigure}{r}{0.5\textwidth}
%\centering %\centering
@@ -532,7 +559,7 @@ transportation solenoid, up to the first 90\si{\degree}.
\begin{SCfigure} \begin{SCfigure}
\centering \centering
\caption{Layout of the COMET Phase-I, the target and detector solenoid are \caption{Layout of the COMET Phase-I, the target and detector solenoid are
placed after the first 90\si{\degree}~bend.} placed after the end of the first \ang{90} bend.}
\includegraphics[width=0.4\textwidth]{figs/comet_phase1_layout} \includegraphics[width=0.4\textwidth]{figs/comet_phase1_layout}
\label{fig:comet_phase1_layout} \label{fig:comet_phase1_layout}
\end{SCfigure} \end{SCfigure}
@@ -545,11 +572,11 @@ The COMET Phase-I has two major goals:
and physics background from muon DIO. Straw tube trackers and crystal and physics background from muon DIO. Straw tube trackers and crystal
calorimeter with the same technology in the full COMET will be used, thus calorimeter with the same technology in the full COMET will be used, thus
these detectors can be regarded as the final prototype. these detectors can be regarded as the final prototype.
\item Search for \mueconv with an intermediate sensitivity of \sn{3.1}{-15}, \item Search for \mueconv with an intermediate single event sensitivity of
a two orders of magnitude improvement from the SINDRUM-II limit. To realise \num{3.1E-15}, a two orders of magnitude improvement from the SINDRUM-II
this goal, two options for detectors are being considered, either a reused limit. Another dedicated detector system (described in
of the detectors for background measurements, or a dedicated detector. \cref{sub:detectors_for_mueconv_search_in_the_phase_i}) is considered for
The latter will be described in detail later. this physics measurement.
\end{enumerate} \end{enumerate}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -558,11 +585,11 @@ The COMET Phase-I has two major goals:
Proton beam for the Phase-I differs only in beam power compares to that of the Proton beam for the Phase-I differs only in beam power compares to that of the
full COMET. It is estimated that a beam power of full COMET. It is estimated that a beam power of
3.2~\si{\kilo\watt}~$=$~8~\si{\giga\electronvolt}~$\times$~0.4~\si{\micro\ampere}~(or 3.2~\si{\kilo\watt}~$=$~8~\si{\giga\electronvolt}~$\times$~0.4~\si{\micro\ampere}~(or
\sn{2.5}{12} protons\si{\per\second}) will be enough for beam properties \sn{2.5}{12} protons per second) will be enough for beam properties
study and achieving the physics goal of this stage. study and achieving the physics goal of this stage.
Starting from a lower intensity is also suitable for performing accelerator Starting from a lower intensity is also suitable for performing accelerator
studies that are needed to realise 8~\si{\giga\electronvolt} beam extraction from studies that are needed to realise 8~\si{\giga\electronvolt} beam extraction
the J-PARC main ring. from the J-PARC main ring.
% subsection proton_beam_for_the_comet_phase_i (end) % subsection proton_beam_for_the_comet_phase_i (end)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\subsection{Pion production and transportation solenoids} \subsection{Pion production and transportation solenoids}
@@ -579,7 +606,7 @@ A correction dipole filed of 0.05 T is also applied to improve the pion yield.
The pion/muon beam line for COMET Phase-I consists of the pion capture solenoid The pion/muon beam line for COMET Phase-I consists of the pion capture solenoid
section (CS), muon transport solenoid section (TS) up to the first section (CS), muon transport solenoid section (TS) up to the first
90\si{\degree}~bending, and a set of matching solenoids (see 90\si{\degree}~bending, and a set of matching solenoids (see
Figure~\ref{fig:comet_phase1_magnets}). At the end of the muon beam line, the \cref{fig:comet_phase1_magnets}). At the end of the muon beam line, the
detectors and the detector solenoid (DS) are installed. To reduce beam detectors and the detector solenoid (DS) are installed. To reduce beam
backgrounds, a beam collimator is placed upstream of the detector solenoid. backgrounds, a beam collimator is placed upstream of the detector solenoid.
\begin{figure}[htb] \begin{figure}[htb]
@@ -599,7 +626,7 @@ backgrounds, a beam collimator is placed upstream of the detector solenoid.
As mentioned, two types of detectors are considered for physics measurements in As mentioned, two types of detectors are considered for physics measurements in
the Phase-I. The dedicated detector system consists of a cylindrical drift the Phase-I. The dedicated detector system consists of a cylindrical drift
chamber (CDC), a trigger hodoscope, a proton absorber and a detector solenoid chamber (CDC), a trigger hodoscope, a proton absorber and a detector solenoid
(Figure~\ref{fig:comet_phase1_cydet}). (\cref{fig:comet_phase1_cydet}).
The whole system is referred as cylindrical detector system (CyDet) in the The whole system is referred as cylindrical detector system (CyDet) in the
COMET's documentation. The CyDet has advantages that low momentum particles for COMET's documentation. The CyDet has advantages that low momentum particles for
the stopping target will not reach the detector, thus the hit rates are kept the stopping target will not reach the detector, thus the hit rates are kept
@@ -614,26 +641,28 @@ CyDet.
\label{fig:comet_phase1_cydet} \label{fig:comet_phase1_cydet}
\end{figure} \end{figure}
\subsubsection{CDC configuration}
\label{ssub:CDC configuration}
The CDC is the main tracking detector that provides information for The CDC is the main tracking detector that provides information for
reconstruction of charged particle tracks and measuring their momenta. The key reconstruction of charged particle tracks and measuring their momenta. The key
parameters for the CDC are listed in the parameters for the CDC are listed in the
Table~\ref{tab:comet_phase1_cdc_params}. \cref{tab:comet_phase1_cdc_params}.
Trigger hodoscopes are placed at both upstream and downstream ends of the CDC. Trigger hodoscopes are placed at both upstream and downstream ends of the CDC.
An absorber is placed concentrically with respect to the CDC axis to A proton absorber is placed concentrically with respect to the CDC axis to
reduce potential high rates caused by protons emitted after nuclear muon reduce potential high rates caused by protons emitted after nuclear muon
capture in the stopping target. capture in the stopping target.
The CDC covers the region The CDC covers the region
from \SIrange{500}{831}{\milli\meter}~in the radial direction. The length from \SIrange{500}{831}{\milli\meter}~in the radial direction. The length
of the CDC is 1500~\si{\milli\meter}. The inner wall is made of of the CDC is 1500~\si{\milli\meter}. The inner wall is made of
a 100~\si{\micro\meter}-thick aluminised Mylar. The end-plates will be conical a 500-\si{um}-thick carbon fibre reinforced plastic (CFRP, density
in shape and about 10~\si{\milli\meter}-thick to support the feedthroughs. The outer \SI{1.57}{\gram\per\cubic\m}). The end-plates will
wall is be conical in shape and about 10-\si{\mm}-thick to support the
made of 5~\si{\milli\meter}~carbon fibre reinforced plastic (CFRP). feedthroughs. The outer wall is made of 5-\si{\mm} CFRP.
The CDC is arranged in 20 concentric sense layers with alternating positive and The CDC is arranged in 20 concentric sense layers with alternating positive and
negative stereo angles. The sense wires are made of gold-plated tungsten, negative stereo angles. The sense wires are made of gold-plated tungsten,
30~\si{\micro\meter} in diameter, tensioned to 50~\si{\gram}. The field wires \SI{25}{\um} in diameter, tensioned to \SI{50}{\gram}. The field wires
are uncoated aluminium wires with a diameter of 80~\si{\micro\meter}, at the same are uncoated aluminium wires with a diameter of 80~\si{\micro\meter}, at the same
tension of \SI{50}{\gram}. A high voltage of $1700\sim1900$~\si{\volt} will be tension of \SI{50}{\gram}. A high voltage of $1700\sim1900$~\si{\volt} will be
applied to the sense wires with the field wires at ground potential, giving an applied to the sense wires with the field wires at ground potential, giving an
@@ -674,37 +703,69 @@ these configurations, an intrinsic momentum resolution of
\label{tab:comet_phase1_cdc_params} \label{tab:comet_phase1_cdc_params}
\end{table} \end{table}
The maximum usable muon beam intensity will be limited by the detector hit \subsubsection{Hit rate on the CDC}
\label{ssub:hit_rate_on_the_cdc}
The maximal usable muon beam intensity will be limited by the detector hit
occupancy. Charge particles with transversal momentum greater than 70 occupancy. Charge particles with transversal momentum greater than 70
\si{\mega\electronvolt\per\cc} are expected to reach the CDC. Those particles are: \si{\mega\electronvolt\per\cc} are expected to reach the CDC. Those include:
protons emitted from nuclear muon capture, and electrons from muon decay in protons emitted from nuclear muon capture, and electrons from muon decay in
orbit. It is calculated that the hit rate due to proton emission dominates, orbit (DIO). It is calculated that the hit rate due to proton emission dominates,
where the highest rate is 11~\si{\kilo\hertz\per}cell compares to where the highest rate is \SI{11}{\kHz\per}cell compares to
5~\si{\kilo\hertz\per} \SI{5}{\kHz\per}cell contributing from DIO electrons. Another potential issue
cell contributing from DIO electrons. Another potential issue caused by protons %%TODO check the hit rates against TDR
is the ageing effect on the CDC as they leave about a 100 times larger caused by protons is the ageing effect on the CDC as they leave about a 100
times larger
energy deposit than the minimum ionisation particles. energy deposit than the minimum ionisation particles.
%%TODO integration charge ...
For those reasons, we plan to install an absorber to reduce the rate of protons For those reasons, we plan to install a proton absorber to reduce the rate of
reaching the CDC. However, there is no experimental data available for the rate protons reaching the CDC. However, there is no experimental data available for
the rate
of protons emitted after muon capture in aluminium. In the design of the COMET 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 Phase-I, we use a conservative estimation of the rate of protons from energy
spectrum of charged particles emitted from muon capture in spectrum of charged particles emitted from muon capture in
$^{28}$Si~\cite{SobottkaWills.1968}. The baseline design for the proton $^{28}$Si~\cite{SobottkaWills.1968}. The baseline design for the proton
absorber is 1.0~\si{\milli\meter}-thick CFRP, which contributes absorber is 1.0~\si{\milli\meter}-thick CFRP, making the total thickness
195~\si{\kilo\electronvolt\per\cc} to the momentum resolution of reconstructed of material before the sensitive region is \SI{1.5}{\mm} in CFRP. In this
track. configuration, the inner wall and the proton absorber deteriorate the momentum
resolution of the reconstructed track to 195~\si{\kilo\electronvolt\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@{}}
\toprule
\textbf{Absorber }& \textbf{Proton }& \textbf{Momentum }\\
\textbf{thickness }& \textbf{hit rate }& \textbf{resolution }\\
(\si{\um}) & (\si{\kHz}) & (\si{\keV\per\cc}) \\
\midrule
0 & 130 & 131 \\
0.5 & 34 & 167 \\
1.0 & 11 & 195 \\
1.5 & 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}.}
\label{tab:comet_absorber_impact}
\end{table}
In order to obtain a better understanding of the protons emission, and then In order to obtain a better understanding of the protons emission, and then
further optimisation of the CDC, a dedicated experiment to measure proton further optimisation of the CDC, a dedicated experiment to measure proton
emission rate and energy spectrum is being carried out at PSI. This experiment emission rate and energy spectrum is being carried out at PSI. This experiment
is described in detail in next chapters. 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
protons emitted.
% subsection detectors_for_mueconv_search_in_the_phase_i (end) % subsection detectors_for_mueconv_search_in_the_phase_i (end)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\subsection{Sensitivity of the \mueconv search in the Phase-I} \subsection{Sensitivity of the \mueconv search in the Phase-I}
\label{sub:sensitivity_of_the_mueconv_search_in_the_phase_i} \label{sub:sensitivity_of_the_mueconv_search_in_the_phase_i}
The SES for the Phase-I is given by The SES for the Phase-I is given by
the Equation~\ref{eq:mue_sensitivity}. Using $N_{\mu} = 1.3\times 10^{16}$, the \eqref{eq:mue_sensitivity}. Using $N_{\mu} = 1.3\times 10^{16}$,
$f_{\textrm{cap}} = 0.61$, and $A_e = 0.043$ from MC study for the Phase-I, the $f_{\textrm{cap}} = 0.61$, and $A_e = 0.043$ from MC study for the Phase-I, the
SES becomes: SES becomes:
\begin{equation} \begin{equation}
@@ -715,10 +776,11 @@ SES becomes:
\subsection{Time line of the COMET Phase-I and Phase-II} \subsection{Time line of the COMET Phase-I and Phase-II}
\label{sub:time_line_of_the_phase_i} \label{sub:time_line_of_the_phase_i}
We are now in the construction stage of the COMET Phase-I, which is planned to We are now in the construction stage of the COMET Phase-I, which is planned to
be finished by the end of 2016. We will carry out engineering run in 2016, be finished in the middle of 2016. We will carry out engineering run in the
second half of 2016,
and subsequently, physics run in 2017. A beam time of 90 days is expected to and subsequently, physics run in 2017. A beam time of 90 days is expected to
achieve the goal sensitivity of the Phase-I. An anticipated schedule for the achieve the goal sensitivity of the Phase-I. An anticipated schedule for the
COMET, both Phase-I and Phase-II, is shown in Figure~\ref{fig:sched}. COMET, both Phase-I and Phase-II, is shown in \cref{fig:sched}.
\begin{figure}[tbh] \begin{figure}[tbh]
\centering \centering
\includegraphics[width=0.8\textwidth]{figs/sched} \includegraphics[width=0.8\textwidth]{figs/sched}

0
thesis/figs/sched.png → thesis/figs/old_sched.png
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thesis/thesis.bib
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@@ -161,11 +161,11 @@
} }
@TechReport{COMET.2012, @TechReport{COMET.2012,
Title = {Experimental Proposal for Phase-I of the COMET Title = {Experimental Proposal for Phase-I of the COMET Experiment at J-PARC},
Experiment at J-PARC},
Author = {R. Akhmetshin and A. Bondar and L. Epshteyn and Author = {R. Akhmetshin and A. Bondar and L. Epshteyn and
G. Fedotovich and D. Grigoriev and V. Kazanin and A. Ryzhenenkov and G. Fedotovich and D. Grigoriev and V. Kazanin and A. Ryzhenenkov and
D. Shemyakin and Yu. Yudin and others}, D. Shemyakin and Yu. Yudin and others},
Institution = {KEK},
Year = {2012}, Year = {2012},
Month = {7}, Month = {7},
Number = {KEK/J-PARC-PAC 2012-10}, Number = {KEK/J-PARC-PAC 2012-10},
@@ -334,6 +334,7 @@
Volume = {729}, Volume = {729},
Doi = {http://dx.doi.org/10.1016/j.nuclphysa.2003.11.003}, Doi = {http://dx.doi.org/10.1016/j.nuclphysa.2003.11.003},
File = {Published version:AudiWapstra.etal.2003.pdf:PDF},
ISSN = {0375-9474}, ISSN = {0375-9474},
Owner = {NT}, Owner = {NT},
Timestamp = {2014-10-26}, Timestamp = {2014-10-26},
@@ -657,16 +658,49 @@
Timestamp = {2014-04-03} Timestamp = {2014-04-03}
} }
@Article{COMET.2009, @Article{CiriglianoKitano.etal.2009,
Title = {Conceptual design report for experimental search for lepton flavor violating $\mu$-- e- conversion at sensitivity of 10^{-16} with a slow-extracted bunched proton beam}, Title = {Model discriminating power of $\mu\rightarrow e$ conversion in nuclei},
Author = {COMET}, Author = {Cirigliano, Vincenzo and Kitano, Ryuichiro and Okada, Yasuhiro and Tuzon, Paula},
Journal = {KEK Report}, Journal = {Phys. Rev. D},
Year = {2009}, Year = {2009},
Pages = {2009},
Volume = {10}, Month = {Jul},
Pages = {013002},
Volume = {80},
Doi = {10.1103/PhysRevD.80.013002},
File = {Published version:CiriglianoKitano.etal.2009.pdf:PDF},
Issue = {1},
Numpages = {13},
Owner = {NT},
Publisher = {American Physical Society},
Timestamp = {2014-10-29},
Url = {http://link.aps.org/doi/10.1103/PhysRevD.80.013002}
}
@TechReport{COMET.2014,
Title = {COMET Phase-I Technical Design Report},
Author = {COMET},
Institution = {KEK},
Year = {2014},
Month = {9},
Type = {Report},
Owner = {NT}, Owner = {NT},
Timestamp = {2014-07-13} Timestamp = {2014-10-29}
}
@TechReport{COMET.2009,
Title = {Conceptual Design Report for experimental search for lepton flavor violating $\mu^- - e^-$ conversion at sensitivity of $10^{-16}$ with a slow-extracted bunched proton beam},
Author = {COMET},
Institution = {KEK},
Year = {2009},
Type = {Report},
Owner = {NT},
Pages = {2009},
Timestamp = {2014-07-13},
Volume = {10}
} }
@Article{ConfortoConversi.etal.1962, @Article{ConfortoConversi.etal.1962,

4
thesis/thesis.tex
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@@ -30,8 +30,8 @@ for the COMET experiment}
\mainmatter \mainmatter
%\input{chapters/chap1_intro} %\input{chapters/chap1_intro}
\input{chapters/chap2_mu_e_conv} %\input{chapters/chap2_mu_e_conv}
%\input{chapters/chap3_comet} \input{chapters/chap3_comet}
%\input{chapters/chap4_alcap_phys} %\input{chapters/chap4_alcap_phys}
%\input{chapters/chap5_alcap_setup} %\input{chapters/chap5_alcap_setup}
%\input{chapters/chap6_analysis} %\input{chapters/chap6_analysis}