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Title: Measurements of the proton elastic-form-factor ratio {mu}{sup p}G{sup p}{sub E}/G{sup p}{sub M} at low momentum transfer.

Abstract

High-precision measurements of the proton elastic form-factor ratio, {mu}{sub p}G{sup p}E/G{sup p}M, have been made at four-momentum transfer, Q{sup 2}, values between 0.2 and 0.5 GeV{sup 2}. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q{sup 2} range the deviation from unity is primarily due to G{sup p}E being smaller than expected.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); National Science Foundation (NSF); Israel Science Foundation; Korea Research Foundation; US-Israeli Bi-National Science Foundation
OSTI Identifier:
958533
Report Number(s):
ANL/PHY/JA-59493
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US1000207
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. Lett.; Journal Volume: 99; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; MOMENTUM TRANSFER; PROTONS; PHYSICS

Citation Formats

Ron, G., Glister, J., Lee, B., Allada, K., Armstrong, W., Arrington, J., Physics, Tel Aviv Univ., St. Mary's Univ., Dalhousie Univ., Seoul National Univ., Univ. of Kentucky, Temple Univ., and The Jefferson Lab Hall A Collaboration. Measurements of the proton elastic-form-factor ratio {mu}{sup p}G{sup p}{sub E}/G{sup p}{sub M} at low momentum transfer.. United States: N. p., 2007. Web. doi:10.1103/PhysRevLett.99.202002.
Ron, G., Glister, J., Lee, B., Allada, K., Armstrong, W., Arrington, J., Physics, Tel Aviv Univ., St. Mary's Univ., Dalhousie Univ., Seoul National Univ., Univ. of Kentucky, Temple Univ., & The Jefferson Lab Hall A Collaboration. Measurements of the proton elastic-form-factor ratio {mu}{sup p}G{sup p}{sub E}/G{sup p}{sub M} at low momentum transfer.. United States. doi:10.1103/PhysRevLett.99.202002.
Ron, G., Glister, J., Lee, B., Allada, K., Armstrong, W., Arrington, J., Physics, Tel Aviv Univ., St. Mary's Univ., Dalhousie Univ., Seoul National Univ., Univ. of Kentucky, Temple Univ., and The Jefferson Lab Hall A Collaboration. Mon . "Measurements of the proton elastic-form-factor ratio {mu}{sup p}G{sup p}{sub E}/G{sup p}{sub M} at low momentum transfer.". United States. doi:10.1103/PhysRevLett.99.202002.
@article{osti_958533,
title = {Measurements of the proton elastic-form-factor ratio {mu}{sup p}G{sup p}{sub E}/G{sup p}{sub M} at low momentum transfer.},
author = {Ron, G. and Glister, J. and Lee, B. and Allada, K. and Armstrong, W. and Arrington, J. and Physics and Tel Aviv Univ. and St. Mary's Univ. and Dalhousie Univ. and Seoul National Univ. and Univ. of Kentucky and Temple Univ. and The Jefferson Lab Hall A Collaboration},
abstractNote = {High-precision measurements of the proton elastic form-factor ratio, {mu}{sub p}G{sup p}E/G{sup p}M, have been made at four-momentum transfer, Q{sup 2}, values between 0.2 and 0.5 GeV{sup 2}. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q{sup 2} range the deviation from unity is primarily due to G{sup p}E being smaller than expected.},
doi = {10.1103/PhysRevLett.99.202002},
journal = {Phys. Rev. Lett.},
number = 2007,
volume = 99,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • High-precision measurements of the proton elastic form-factor ratio, {mu}{sub p}G{sub E}{sup p}/G{sub M}{sup p}, have been made at four-momentum transfer, Q{sup 2}, values between 0.2 and 0.5 GeV{sup 2}. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q{sup 2} range the deviation from unity is primarily due to G{sub E}{sup p} being smaller than expected.
  • High precision measurements of the proton elastic form factor ratio have been made at four-momentum transfers, Q^2, between 0.2 and 0.5 GeV^2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q^2 range the deviation from unity is primarily due to GEp being smaller than the dipole parameterization.
  • Here, we report a new high precision measurement of the proton elastic form factor ratio μpGE/GM for the four-momentum transfer squared Q 2 = 0.3-0.7 (GeV/c) 2. The measurement was performed at Jefferson Lab (JLab) in Hall A using recoil polarimetry. With the achieved ~1% total uncertainty, the new data clearly show that the deviation of the ratio μpGE/GM from unity observed in previous polarization measurements at high Q 2 continues down to the lowest Q 2 value of this measurement. The updated global fit that includes the new results yields in this Q 2 range an electric (magnetic) formmore » factor ~2% smaller (~1% larger) than the previous global fit. We obtain new extractions of the proton electric and magnetic radii, which are (r E 2) 1/2 = 0.875 ± 0.010 fm and (r M 2) 1/2 = 0.867 ± 0.020 fm. Moreover, the charge radius is consistent with other recent extractions based on the electron-proton interaction, including the atomic hydrogen Lamb shift measruements, which suggests a missing correction in the comparison of measurements of the proton charge radius using electron probes and the recent extraction from the muonic hydrogen Lamb shift.« less
  • We present measurements of the ratio of the proton elastic electromagnetic form factors, {mu}{sub p}G{sub Ep}/G{sub Mp}. The Jefferson Lab Hall A Focal Plane Polarimeter was used to determine the longitudinal and transverse components of the recoil proton polarization in ep elastic scattering; the ratio of these polarization components is proportional to the ratio of the two form factors. These data reproduce the observation of Jones [Phys. Rev. Lett. 84, 1398 (2000)], that the form factor ratio decreases significantly from unity above Q{sup 2}=1 GeV{sup 2}.