diff --git a/APPC2013/Answer to the reviewer.pdf b/APPC2013/Answer to the reviewer.pdf new file mode 100644 index 0000000..deeb45b Binary files /dev/null and b/APPC2013/Answer to the reviewer.pdf differ diff --git a/APPC2013/Ref_cEbu61VYUP_CYDxeKrRf1.pdf b/APPC2013/Ref_cEbu61VYUP_CYDxeKrRf1.pdf new file mode 100644 index 0000000..c4e5395 Binary files /dev/null and b/APPC2013/Ref_cEbu61VYUP_CYDxeKrRf1.pdf differ diff --git a/APPC2013/abstract/abstract.tex b/APPC2013/abstract/abstract.tex index 360658c..0927ff7 100644 --- a/APPC2013/abstract/abstract.tex +++ b/APPC2013/abstract/abstract.tex @@ -124,7 +124,7 @@ 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 +initial data taking in around 2017. This paper provides some highlights among ongoing R\&D activities. %Charged lepton flavor violation (CLFV) has attracted much attention from @@ -157,18 +157,18 @@ ongoing R\&D activities. ~\\ -~[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.\\ +~[1] D.~Bryman (The COMET collaboration): ``An experimental + search for lepton flavor violating $\mu^- - e^-$ conversion at sensitivity of + $10^{-16}$ with a slow-extracted bunched proton beam'', J-PARC Proposal, + 2007. \\ -~[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) + +~[2] W.~Bertl (SINDRUM-II collaboration): Eur. Phys. J. C \textbf{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-~[3] Y.~Kuno {\it et al.} (COMET collaboration), ``Letter of - Intent of Phase-I for the COMET Experiment at J-PARC'', unpublished, March - 2012. +~[3] R. Akhmetshin (The COMET collaboration): ``Experimental + proposal for Phase--I of the COMET experiment at J-PARC'', KEK/J-PARC-PAC + 2012-10. %%% diff --git a/APPC2013/proceeding/proceeding.tex b/APPC2013/proceeding/proceeding.tex index fd55300..059acbb 100644 --- a/APPC2013/proceeding/proceeding.tex +++ b/APPC2013/proceeding/proceeding.tex @@ -53,29 +53,30 @@ This is an unobservably tiny branching ratio so that any experimental evidence of CLFV would be a clear sign of new physics beyond the SM. -Among CLFV processes, one of the most prominent one is +One of the most prominent CLFV processes is a process of coherent muon-to-electron conversion ($\mu -- e$ conversion) in the field of a nucleus: \muecaz. $\mu - e$ conversion would -occur in the following manner. Stopped muons are quickly captured by atoms -($~10^{-10}$ s) and cascade down to the 1S orbitals. There, they can undergo: +- e$ conversion) in the field of a nucleus: \muecaz. When muons are stopped in +a target, they are quickly +captured by atoms ($~10^{-10}$ s) and cascade down to the 1S orbitals. There, +they can undergo: (a) ordinary decay, (b) weak capture, $\mu^- p \rightarrow \nu_\mu n$, or (c) $\mu - e$ conversion, \muec. The last of these reactions is a CLFV process where lepton flavor numbers, $L_\mu$ and $L_e$, are violated by one unit. The $\mu - e $ conversion is attractive both from theoretical and experimental points of view. Many extensions of the SM predict that it would has sizeable -branching ratio~\cite{altman}, one possible supersymmetric contribution to the +branching ratio~\cite{altman}. One possible supersymmetric contribution to the $\mu - e$ conversion is shown in Fig.~\ref{fig:susy_contr}. Experimentally, the -simplicity and distintive signal, a mono-energetic electron of energy: +simplicity and distintive signal, a mono-energetic electron of energy $E_{e}$: \[ - E_{mec} = m_{\mu} - B_{\mu}(Z, A) - R(A) \simeq \textrm{105 MeV}, + E_{e} = m_{\mu} - B_{\mu}(Z, A) - R(A) \simeq \textrm{105 MeV}, \] where $m_\mu$ is the muon mass, $B_\mu(Z, A)$ is the muonic atom binding energy, and $R(A)$ is the nuclear recoil energy, allow experimental searches -without accidentals and extremely high rates. As a result, one of the best -limit of CLFV searches comes from a search for $\mu - e$ conversion in muonic -gold done by -the SINDRUM--II collaboration: \sindrumlimit~\cite{sindrumii}. +without accidentals and thus in extremely high rates. As a result, one of the +best upper limits of CLFV searches comes from a search for $\mu - e$ conversion +in muonic gold done by the SINDRUM--II collaboration: +\sindrumlimit~\cite{sindrumii}. \begin{figure}[tbh] \centering @@ -91,31 +92,32 @@ $10^{-17}$} \subsection{The COMET experiment} At the Japan Proton Accelerator Research Complex (J-PARC), an experiment to search for \muec~conversion, which is called COMET (COherent Muon to Electron -Transition) has been proposed~\cite{comet07}. The experiment received Stage--1 +Transition), has been proposed~\cite{comet07}. The experiment received Stage--1 approval in -2009. Utilising a proton beam of 56 kW from the +2009. Utilising a proton beam of 56 kW (8 GeV $\times$ 7 $\mu$A) from the J-PARC main ring, the COMET aims for a single event sensitivity of $3 \times 10^{-17}$, which is 10000 times better than the current best -limit at SINDRUM--II. +limit at SINDRUM--II. As of April 2013, the COMET collaboration has 117 +members in 27 institutes from 12 countries. -The COMET experiment is designed to be carried out at the Nuclear and Particle -Experimental Hall (NP Hall) using a bunched proton beam that is +The COMET experiment is designed to be carried out at the Hadron +Experimental Facility using a bunched proton beam that is slowly-extracted from the J-PARC main ring. The experimental set-up consists of a dedicated proton beam line, a muon beam transport section, and a detector -section. The muon beam section is composed of a superconducting pion capture -solenoid with high magnetic field. The detector section has muon stopping -targets, an electron transport beam line for $\mu - e$ conversion signals, +section. The muon beam section is composed of superconducting magnets: pion +capture solenoid and a pion/muon transport solenoid. The +detector section has a multi-layered muon stopping target, an electron +transport beam line for $\mu - e$ conversion signals, followed by detector systems. \subsection{Staging approach at the COMET} -The COMET collaboration, which has 117 collaborators in 27 institutes from -12 countries as of April 2013, has adopted a staging approach with two +The COMET collaboration has adopted a staging approach with two phases~\cite{comet12}. COMET Phase--I is scheduled to have an engineering run in 2016, followed by a physics run in 2017. Phase--I should achieve a sensitivity of $3 \times 10^{-15}$, 100 times better than that of SINDRUM--II; while -Phase--II will reach a sensitivity of $3 \times 10^{-17}$, which is -comparable to the Mu2e project at Fermilab~\cite{mu2e08}. +Phase--II will reach a sensitivity of $2.6 \times 10^{-17}$, which is +competitive with the Mu2e project at Fermilab~\cite{mu2e08}. A schematic layout of the COMET experiment with its two phases is shown in Fig.~\ref{fig:comet_phase1}, and a schedule for two phases is shown in Fig.~\ref{fig:sched}. @@ -129,7 +131,7 @@ Fig.~\ref{fig:sched}. \begin{figure}[tbh] \centering -\includegraphics[width=\textwidth]{figs/sched} +\includegraphics[width=0.8\textwidth]{figs/sched} \caption{The anticipated schedule of the COMET experiment.} \label{fig:sched} \end{figure} @@ -142,32 +144,32 @@ COMET Phase--I has two major goals: \times 10^{-15}$. \end{itemize} -In order to realized the goals, COMET Phase--I proposes to have two systems of -detector. A straw tube detector and electromagnetic calorimeter will be used +In order to realize the goals, COMET Phase--I proposes to have two systems of +detector. A straw tube detector and an electromagnetic calorimeter will be used for the background study. For the $\mu-e$ conversion search, a cylindrical drift chamber (CDC) will be built. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{Status of the COMET experiment} -The COMET collaboration is working very hard to realize the schedule with the -physics run in 2017. Some R\&D activities are hightlighted as follow. +The COMET collaboration is working very hard toward the +physics run in 2017. Some R\&D activities are hightlighted as follows. \subsection{COMET beam line and experimental hall} Budget for construction of the COMET beam line and experimental hall has been approved. Construction has been started in 2013 and is expected to be completed by spring 2015. Production of coils for superconducting magnets will begin in -July, 2013. Design of radiation shielding and pion production target are in -progress. +July, 2013. Design of the radiation shielding and the pion production target +are in progress. \subsection{R\&D for detectors} \subsubsection{Cylindrical drift chamber} The CDC is a detector dedicated for COMET Phase--I to maximize the experimental -sensitivity for the $\mu-e$ conversion search. A prototype CDC would be ready +sensitivity for the $\mu-e$ conversion search. A prototype CDC will be ready for testing at Osaka University in September, 2013. Designing for the real -detector is ongoing based on simulation study and experiments with a test +detector is ongoing based on simulation studies and experiments with a test chamber and test readout boards. -One designing issue with the CDC is its single hit rate would be dominated by -protons emitted after muons are captured in the target. The lack of +One designing issue with the CDC is that its single hit rate would be dominated +by protons emitted after muons are captured in the target. The lack of experimental data on protons from Al target makes it difficult to optimize the inner wall of the CDC to achieve best momentum resolution. In order to provide input for this optimization, a dedicated @@ -179,14 +181,15 @@ a joint effort between COMET and Mu2e. The straw tube tracker for background study in COMET Phase--I is being developed with expertise from JINR, Russia group in NA62 experiment. A KEK-JINR collaboration has been formed to produce a prototype tracker. R\&D for this -prototype would be completed in 2013. Design works and construction of the real +prototype will be completed in 2013. Design works and construction of the real detector is ongoing. \subsubsection{Electromagnetic calorimeter} An electromagnetic calorimeter will be used in the COMET Phase--II as a trigger -detector that triggers on 105 MeV electrons. Currently, two types of crystal +detector that triggers on 105 MeV electrons, as well as in the Phase--I for the +background study. Currently, two types of crystal are considered for this calorimeter: GSO and LYSO. Beam tests of calorimeter -prototypes with APD readout are underway. The choice of crystal would be made +prototypes with APD readout are underway. The choice of crystal will be made in a few months. A prototype electronics system for the detector has been developed by BINP, Novosibirsk, Russia group, and is being evaluated in the beam tests at J-PARC. @@ -195,18 +198,23 @@ beam tests at J-PARC. Software used to simulate and analyse data is crucial to the success of the COMET experiment. The COMET software group has set up a new software framework called ICEDUST (Integrated COMET Experiment Data User Software Toolkit). The -framework includes an improved simulation for the experiment. It also +framework includes an improved simulation for the experiment. Some improvements +are: the ability to run the simulation on a computing grid for large simulation +data production, and an optimized +beam line with a realistic magnetic field map from the manufacturer of the +superconducting magnets. The ICEDUST also has modules to perform calibration, reconstruction and analysis of both Monte-Carlo outputs and experimental data in a unified way. Documentations and -implementations of ICEDUST are underway. +implementations of the ICEDUST are underway. \section{Summary} The COMET (J-PARC E21) experiment is going to push the limit of experimental searches for CLFV $\mu-e$ conversion process, a very promising probe for new -physics beyond the SM. Heavy R\&D activities are ongoing to realize the physics -run of its first stage, COMET Phase--I, in the year of 2017 with an immediate -goal: two orders of magnitude improvement in the single event sensitivity -compares the the current best limit. +physics beyond the SM. +The first stage, COMET Phase--I, will improve the upper limit by two orders of +magnitude to a single event sensitivity of $3\times10^{-15}$. +Heavy R\&D activities are ongoing to realize the physics +run of the COMET Phase--I in the year of 2017. %\appendix %\section{} %