2nd draft, change figures according to Kuno-san's suggestion

This commit is contained in:
nam
2013-03-10 03:47:52 +09:00
parent 2f5a67a7cc
commit 5d09ec0100
5 changed files with 104 additions and 72 deletions

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@@ -5,52 +5,63 @@
\begin{column}{\onecolwid}% the right size for a 3-column layout
%--abstract block--------------------------------------------------------
\begin{alertblock}{Introduction}
Charged lepton flavor violation (cLFV) has yet to be observed and is
known to be sensitive to new physics beyond the Standard Model (SM).
Various extensions of the SM predicts that cLFV occurs at a detectable
\textcolor{red}{Charged lepton flavor violation (cLFV)} has yet to be
observed and is known to be sensitive to new physics beyond the
Standard Model (SM).
Various extensions of the SM predicts that cLFV occurs at some detectable
branching ratio. Therefore, from experimental point of view, it is
attractive to search for cLFV with more powerful beams and better
detection technologies.
very attractive to search for cLFV with more powerful beams and better
detection techniques.
Among the cLFV processes, $\mu-e$ conversion, a coherent neutrino-less
conversion of muon to electron in the presence of a nucleus: \muecaz,
is our interest. We have proposed a new search for $\mu -e$ conversion
at J-PARC, the E21 experiment - \textcolor{red}{COMET}(
\textcolor{red}{COherent Muon to Electron Transition}). The single
event sensitivity (SES) of COMET will be $2.6\times10^{-17}$, which is
event sensitivity (SES) of the COMET will be
\textcolor{red}{$2.6\times10^{-17}$}, which is
10,000
times better than that of the current experimental limit
set by SINDRUM II at $7\times10^{-13}$.
set by SINDRUM II at \textcolor{red}{$7\times10^{-13}$}.
\end{alertblock}
\begin{alertblock}{Staging approach of the COMET}
In order to realize the COMET experiment, a two-stage approach has been
taken. COMET Phase-I aims at an intermediate SES of $3\times10^{-15}$,
which is an improvement of a factor of 100 compares to SINDRUM II. In
addition, the COMET Phase-I will make direct measurement of the proton
beam extinction and other potential background sources for the COMET
Phase-II experiment, using the actual COMET beam line.
taken. The first stage, \textcolor{red}{COMET Phase-I} has two major
goals:
\begin{enumerate}
\item \textcolor{red}{Search for $\mu-e$ conversion}: we aim at an
intermediate SES of \textcolor{red}{$3\times10^{-15}$}, which is an
improvement of a factor of 100 compares to SINDRUM II.
\item \textcolor{red}{Background measurements} for full COMET: make
direct measurement of the proton beam extinction and other
potential background sources, using the actual COMET beam line.
\end{enumerate}
\begin{figure}[h!]
\begin{center}
\includegraphics[width=0.95\onecolwid]{../figs/comet/comet_phase_1}
\includegraphics[width=0.96\onecolwid]{../figs/comet/comet_phase_1}
\end{center}
\caption{Schematic layout of the COMET}
\label{fig:cometscheme}
\end{figure}
The COMET Phase-I funding has been approved. Experimental hall
construction and beam
line design are in progress, and expected to finish in 2015. The layout
of the COMET beam line at Hadron Hall, J-PARC is shown in the Fig.
\ref{fig:cometbeamline}. For the COMET Phase-I, we will
construct the first 90 degrees of the muon beam line before extracting
to the experimental area. Data taking is expected to start around 2016.
Layout of the COMET experiment at Hadron Hall, J-PARC is shown in the
Fig~\ref{fig:cometbeamline}. For the COMET Phase-I, we will construct
the first \textcolor{red}{90 degrees} of the muon beam line before
extracting to the experimental area.
The COMET Phase-I \textcolor{red}{funding has been approved} by KEK.
This will cover
experimental hall and beam line construction. The construction is
expected to finish in 2015, then data taking would start around
2016.
\begin{figure}[h!]
\begin{center}
\includegraphics[width=0.95\onecolwid]{../figs/comet/comet_beamline}
\includegraphics[width=0.940\onecolwid]{../figs/comet/comet_in_hadron_hall}
\end{center}
\vskip1.6ex
\caption{COMET beam line at Hadron hall}
\label{fig:cometbeamline}
\end{figure}
@@ -72,19 +83,21 @@
\begin{center}
\includegraphics[width=0.99\twocolwid]{../figs/comet/comet_phase1_layout.png}
\end{center}
\caption{Schematic lay out of the COMET Phase I}
\caption{Concept of the COMET Phase-I}
\label{fig:phase1}
\end{figure}
\vskip-2ex
\begin{columns}[t,totalwidth=\twocolwid]
\begin{column}{\onecolwid}
\begin{alertblock}{Proton beam}
COMET Phase-I will use an 8 GeV, 0.4 $\mu$A ($2.5 \times 10^{12}$
COMET Phase-I will use an \textcolor{red}{8 GeV, 0.4 $\mu$A} ($2.5 \times 10^{12}$
protons/sec), slowly extracted proton
beam from the J-PARC main ring (MR). One option for the bunch
structure of the proton beam is shown in Fig \ref{fig:pbeam}.
beam from the J-PARC main ring (MR). One proposed configuration for
the bunch structure of the proton beam is shown in
Fig~\ref{fig:pbeam}.
\begin{figure}[]
\includegraphics[width=0.75\onecolwid]{../figs/comet/comet_pbeam_config}
\includegraphics[width=0.65\onecolwid]{../figs/comet/comet_pbeam_config}
\vskip-1.5ex
\caption{COMET proton beam acceleration bunch configuration}
\label{fig:pbeam}
\end{figure}
@@ -92,21 +105,30 @@
\begin{alertblock}{Muon transportation}
The muon beam line of COMET Phase-I includes the pion capture
section and the muon transport section up to the end of first
$90^o$ bend. A high solenoidal field of 5 T is used in the pion
capture section to capture as many pions as possible. Pions and
$90^o$ bend. The field in the superconducting pion capture solenoid
is 5 T. Pions and
muons - produced when pions decay in flight - goes to
a matching section, before going to the transport section with
a 3 T field. A prototype of this system has been built and operated
successfully at Osaka University.
a matching section, before going to the transport solenoid with
a 3 T field. \textcolor{red}{A prototype of this system has been
built and operated successfully at Osaka University.}
Negative muons are selected by a dipole field, which
is created by an additional winding on top of the solenoid
windings. A collimator is placed in front of the detector section
to eliminate high momentum muons (and survival pions).
\begin{figure}[]
\includegraphics[width=0.75\onecolwid]{../figs/comet/mu_momentum_phase1}
\caption{Muon momentum before (upper) and after (lower) the collimator}
\label{fig:mumomentum}
\includegraphics[width=0.70\onecolwid]{../figs/comet/mu_stop_phase1}
\vskip-1.5ex
\caption{Momentum distribution of muons approaching the target
(open histogram) and those stopped by it (red)}
\label{fig:mustop}
\end{figure}
\end{alertblock}
\begin{alertblock}{Schedule}
\begin{figure}[!h]
\includegraphics[width=0.95\onecolwid]{../figs/comet/comet_phase1_sched}
%\caption{Technical driven schedule of COMET Phase-I}
\label{fig:sched}
\end{figure}
\end{alertblock}
\end{column}
@@ -115,41 +137,50 @@
\begin{alertblock}{Detectors for COMET Phase-I}
There will be two detectors for two goals of COMET Phase-I: physics
measurements and background measurements.
\begin{enumerate}
\item \textcolor{red}{$\mu-e$ conversion search:}
There are two candidates for the detector for the
search. \textcolor{red}{Baseline detector is a cylindrical
drift chamber (CDC)}, shown in the detector section in
Fig~\ref{fig:phase1}.
The CDC is chosen because it would help reducing background rate
and hit rate. The alternative option is using the same detector
for background measurements: a tranverse tracker, which is
decribed below.
Detector for background measurements consists of a solenoid magnet,
0.8 - 1 T, 5 straw tube tracker layers and a crystal calorimeter.
This is regarded as a final prototype for Phase-II detector.
The CDC is placed inside a magnetic field of 1 - 1.5 T. It is
tuned to accept particles with momentum larger than 70 MeV/c.
Segmented triger hodoscope is located before the drift chamber,
provides timing signal and reduces protons hit rate on the
chamber. In order to reach the goal SES, energy resolution
requirement for the CDC is \textcolor{red}{1.5 MeV at 105 MeV}.
%\vskip-1ex
\begin{figure}[!h]
\includegraphics[width=0.90\onecolwid]{../figs/comet/comet_signal}
\vskip-1ex
\caption{Signal of $\mu-e$ conversion, electron with
momentum of about 105 MeV/c (red); and background from electron
from muon decay in orbit (blue).}
\label{fig:signal}
\end{figure}
\item \textcolor{red}{Background measurements:}
A \textcolor{red}{tranverse tracker} will be used. It consists
of a solenoid magnet, 0.8
- 1 T, 5 straw tube tracker layers and a crystal calorimeter.
This is regarded as a final \textcolor{red}{prototype for
Phase-II detector}.
\begin{figure}[!h]
\includegraphics[width=0.90\onecolwid]{../figs/comet/comet_p1_det_bg}
\vskip-1ex
\caption{Concept of the detector for background measurements}
\label{fig:phys_det}
\end{figure}
\end{enumerate}
A lot of detector R\&D activities are ongoing: ECAL
with GSO/LYSO crystals and APD readout; prototype of straw tube
tracker; front end electronic board.
\vskip-2ex
\begin{figure}[!h]
\includegraphics[width=0.95\onecolwid]{../figs/comet/comet_p1_det_bg}
\vskip-2ex
\caption{Concept of the detector for background measurements}
\label{fig:phys_det}
\end{figure}
There are two options for the detector for $\mu-e$
conversion search. Baseline detector is a cylindrical drift chamber
(CDC), shown in the detector section in Fig.
\ref{fig:phase1}. The CDC would help reducing background rate and
hit rate. The other option is a transverse tracker, in
which the detector for background measurements will be reused.
The CDC is placed inside a magnetic field of 1 - 1.5 T. The
magnetic field and radial size of the CDC are adjusted to accept
particles with momentum larger than 70 MeV/c. Segmented triger
hodoscope is located before the drift chamber, provides timing
signal and reduces protons hit rate on the chamber. In order to
reach the goal SES, energy resolution requirement for the CDC is
1.5 MeV at 105 MeV.
\end{alertblock}
\begin{alertblock}{Schedule}
\begin{figure}[!h]
\includegraphics[width=0.95\onecolwid]{../figs/comet/comet_phase1_sched}
%\caption{Technical driven schedule of COMET Phase-I}
\label{fig:sched}
\end{figure}
tracker; front end electronic board; calculation and wire
chamber test for CDC; \ldots
\end{alertblock}
\end{column}
\end{columns}

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size=a0, % poster size
scale=1.35 % font scale factor
scale=1.3 % font scale factor
]{beamerposter} % beamer in poster size
%
%--some needed packages--------------------------------------------------------
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%==============================================================================
%==the poster content==========================================================
%==============================================================================

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