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\documentstyle[11pt,apsab]{article}
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\MeetingID{DNP04}
%\DateSubmitted{20040621}
\SubmittingMemberSurname{Zheng}
\SubmittingMemberGivenName{Xiaochao}
%\SubmittingMemberID{60057843}
\SubmittingMemberEmail{xiaochao@jlab.org}
\SubmittingMemberAffil{Argonne National Lab}
\PresentationType{oral}
\SortCategory{13b.}{}{}{}
\begin{document}
\Title{Measurements of $G_E^p/G_M^p$ Using a Polarized Target}
\AuthorSurname{Zheng}
\AuthorGivenName{Xiaochao}
\thanks{mailing address: 12000 Jefferson Avenue, Newport News, VA 23606}
%\AuthorEmail{xiaochao@jlab.org}
\AuthorAffil{Argonne National Lab}
E
\begin{abstract}
The nucleon elastic form factors are important inputs to our
understanding of the nucleon structure and hadronic physics.
However, in the region $Q^2>2$~(GeV/c)$^2$ there is a large
discrepancy between data on the proton $G_E^p/G_M^p$ ratio
obtained using two different techniques - Rosenbluth
separation and polarization transfer. Although recently it
has been shown that the two-photon exchange (TPE) might be
the solution, a full understanding of TPE has not been
achieved. Whether it fully explains the discrepancy in the
large $Q^2$ region and whether there are other mechanisms
that may cause the discrepancy are still unknown. We present
here a different approach aimed at understanding the
$G_E^p/G_M^p$ data. We plan to measure the asymmetry of
elastic ep scattering using a polarized beam and a polarized
proton target, from which $G_E^p/G_M^p$ up to
$Q^2=5.6$~(GeV/c)$^2$ will be extracted using the formalism
of double polarization asymmetries. A proposal has been
submitted to JLab PAC-26. The experimental setup and the
expected uncertainties will be presented. This work is
supported by the U.S. Department of Energy, Office of
Nuclear Physics, under contract No. W-31-109-ENG-38.
\end{abstract}
\end{document}