Jefferson Lab Experiment E01-001
New Measurement of (G_E/G_M) for the proton
Experiment Overview:
- Spokespersons: John Arrington, Argonne National Lab, and Ralph Segel, Northwestern University
- 52 Collaborators from 19 institutions
- Thesis student: Issam Qattan (Northwestern University, expected 2005)
- Data taken in Hall A of Jefferson Lab (May 2002)
- Experiment E01-001 provided new Rosenbluth separation measurements of the
proton electromagnetic form factors at Q^2=2.64, 3.20 and 4.10 GeV^2. Cross
sections were determined by detecting the recoiling proton, in contrast to
previous measurements which detected the scattered electron, which allowed the
relative cross sections to be determined to better than 1%. The ratio G_E/G_M
was determined to 4-8% and was consistent with, but much more precise than,
previous Rosenbluth extractions. They are inconsistent with recent polarization
transfer measurements of similar precision, implying a systematic difference
between the techniques. At the moment, two-photon exchange corrections appear
to be the most likely explanation of the discrepancy.
Contents
- Theses
- Issam A. Qattan, Northwestern University, expected 2005.
- Related experiments
- JLab E05-017 - A measurement of two-photon exchange in unpolarized
elastic electron-proton scattering
- JLab E04-116 - Beyond the Born approximation: A Precise Comparison of positron-proton
and electron-proton Scattering in CLAS
- J. Arrington, A. Afanasev, W. Brooks, K. Joo, B. Raue and L. Weinstein spokespersons:
Full Proposal
- VEPP-III Proposal: Two-photon exchange and elastic scattering of electrons/positron
on the proton
- JLab E04-110: ResR
- Related publications: Two-photon exchange -- (Links are to arXiv abstracts)
- Phenomonology/Theory
- Extraction of two-photon
contributions to the proton form factors - J. Arrington, Phys.
Rev. C71, 015202 (2005)
- Search for evidence of two
photon contributions in elastic electron proton data - E. Tomasi-Gustafsson
and G. I. Gakh, Phys. Rev. C72, 015209 (2005)
- Evidence for two-photon exchange contributions
in electron proton and positron proton elastic scattering - J. Arrington, Phys.
Rev. C69, 032201(R) (2004)
- Implications of the discrepancy
between proton form-factor measurements - J. Arrington, Phys.
Rev. C69, 022201 (2004)
- How well do we know the
electromagnetic form-factors of the proton - J. Arrington, Phys.
Rev. C68, 034325 (2003)
- Theory/Calculations
- How to reconcile the Rosenbluth
and the Polarization transfer method in the measurement of the proton form factors
- P. A. M. Guichon and M. Vanderhaeghen, Phys. Rev. Lett. 91, 142303 (2003)
- Two photon exchange and elastic
electron proton scattering - P. G. Blunden, W. Melnitchouk, and J. A. Tjon, Phys.
Rev. Lett. 91, 142304 (2003)
- Coulomb distortion in high-Q^2
elastic e-p scattering - John Arrington and Ingo Sick, Phys.
Rev. C70, 028203 (2004)
- Delta resonance contribution to two-photon
exchange in electron-proton scattering - S. Kondratyuk, P. G. Blunden, W. Melnitchouk,
and J. A. Tjon, nucl-th/0506026 (2005)
- Two-photon exchange in elastic
electron-nucleon scattering - P. G. Blunden, W. Melnitchouk, and J. A. Tjon,
nucl-th/0506039 (2005)
- Partonic calculation of the two photon
exchange contribution to elastic electron proton scattering at larget momentum transfer
Y. C. Chen, et al., Phys. Rev. Lett 93, 122301 (2004)
- The two-photon exchange contribution
to elastic electron-nucleon scattering at large momentum transfer- A. Afanasev,
et al., Phys. Rev. D72, 0502013 (2005)
- Model independent properties
of two photon exchange in elastic electron proton scattering - M. Rekalo and
E. Tomasi-Gustafsson, Eur. Phys. J. A22, 331 (2004)
This page is maintained by David Potterveld (potterveld 'at' anl.gov
It was last updated May 18, 2001