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\MeetingID{DNP04}

%\DateSubmitted{20040621}

\SubmittingMemberSurname{Zheng}

\SubmittingMemberGivenName{Xiaochao}

%\SubmittingMemberID{60057843}

\SubmittingMemberEmail{xiaochao@jlab.org}

\SubmittingMemberAffil{Argonne National Lab}

\PresentationType{oral}

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\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}