148 lines
4.2 KiB
TeX
148 lines
4.2 KiB
TeX
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\vspace{.0cm}
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{\raggedleft December 10, 2012 \\
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\par}
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\vspace{.5cm}
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\begin{center}
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{\bf\LARGE Study of Muon Capture for\\\vspace{2mm}
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Muon to Electron Conversion Experiments}
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\vspace{.5cm}
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\Large
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AlCap Collaboration
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\vspace{1.5cm}
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%% ML - move this figure to the Intrduction
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% \begin{figure}[h]
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% %\vspace{-40mm}
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% \includegraphics[width=\textwidth]{figs/comet-mu2e.png}
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% \caption{Schematic layouts of the Mu2e (left) and the COMET (right).}
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% \label{fg:mu2ecomet}
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% %\vspace{-5mm}
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% \end{figure}
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% \vspace{10mm}
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\end{center}
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\begin{center}
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%{\tt Preliminary version, final proposal will be uploaded on 12/14/2012}
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%{\bf institutional representatives, please check and update}
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\vspace{5mm}
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D. Alexander\uh,
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D.M. Asner\pnnl,
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E. Barnes\bu,
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R. Bernstein\fnal,
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R. Bonicalzi\pnnl,
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A. Daniel\uh,
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A. Edmonds\ucl,
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A. Empl\uh,
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D. Hertzog\uw,
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Y. Hino\osaka,
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E. Hungerford\uh,
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T. Itahashi\osaka,
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D. Kawall\umass,
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A. Kolakar\bu,
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B. Krikler\icl,
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\underline{P. Kammel\uw},
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K. Kumar\umass,
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\underline{Y. Kuno\osaka},
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A. Kurup\icl,
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M. Lancaster\ucl,
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J. Miller\bu,
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M. Murray\uw,
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T.H. Nam\osaka,
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V. Ruso\fnal,
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H. Sakamoto\osaka,
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A. Sato\osaka,
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M. Schram\pnnl,
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Y. Uchida\icl,
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G. Warren\pnnl,
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F. Wauters\uw,
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P. Winter\anl,
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M. Wing\ucl,
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L. Wood\pnnl
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\vspace{10mm}
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\anl Argonne National Laboratory, Illinois (ANL)
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\bu Boston University, Boston, Massachusetts (BU)
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\fnal Fermilab National Accelerator Laboratory, Batavia, Illinois (FNAL)
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\uh University of Houston, Houston, Texas (UH)
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\icl Imperial College, London, UK (ICL)
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\umass University of Massachusetts, Amhurst, Massachusetts (UMass)
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\osaka Osaka University, Osaka, Japan (OU)
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\pnnl Pacific Northwest National Laboratory, Richland, Washington (PNNL)
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\ucl University College London, London, UK (UCL)
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\uw University of Washington, Seattle, Washington (UW)
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\vspace{15mm}
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Co-spokespersons underlined.
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\end{center}
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\newpage
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\vspace{2cm}
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\begin{center}
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{\bf Abstract}
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\end{center}
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The recent observation that neutrinos oscillate, change flavour, and so have
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mass, requires an extension to the Standard Model (SM) and
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demonstrates that lepton flavour is
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not an absolutely conserved quantity. However, even when accommodating
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finite neutrino mass in a minimal extension
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to the SM, the rate of charged lepton flavour
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violating (CLFV) interactions is predicted to be far too
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small to be observed, ${\cal{O}}(10^{-50})$. Thus, any experimental
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observation of CLFV would be clear evidence of new physics beyond the SM.
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Two new projects will search for the CLFV in
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\muec conversion. They are the Mu2e experiment at FNAL and the
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COMET experiment at J-PARC. Both experiments utilise multi-kW
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pulsed 8$-$9 GeV proton beams to achieve a branching ratio sensitivity lower
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than 10$^{-16}$, that is 10,000 times better than the current best
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limit established by SINDRUM II.
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Both COMET Phase-I and Mu2e are subject to significant backgrounds
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from the products from muon (and pion) nuclear capture. The
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goals of this joint proposal between both Mu2e and COMET
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collaborations are precision measurements of muon
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capture reactions in candidate targets, at levels required
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for the design and optimization of this new generation of experiments.
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The initial focus of this proposal is on the measurement of low energy
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charged particles after muon capture on a nucleus. This process
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constitutes a severe background, and has inadequate
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experimental information available. X-rays and
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gamma-rays will be also observed, in order to verify that this
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technique can be used to determine the number of $\mu$ captures in a
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$\mu \to e$ experiment, and to
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normalize the proposed capture measurements. Finally we propose to
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study both neutron emission after $\mu$ capture and radiative decay of
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the $\mu$ in the nuclear environment as these also provide crucial
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information to be used in the design and simulation of the experiments.\\
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PSI beam quality is critical to provide a pure, low-energy muon beam
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with a small momentum spread. This is especially important for
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charged-particle emission measurements, as thin targets of
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aluminum, silicon and titanium are required so that the emitted
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particles penetrate the targets with minimal energy loss.
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This was a major problem in previous experiments and has prevented the
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extraction of low-energy spectra.
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\newpage
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