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Title: High-precision measurement of the proton elastic form factor ratio μpGE/GM at low Q2

Here, we report a new high precision measurement of the proton elastic form factor ratio μpGE/GM for the four-momentum transfer squared Q2 = 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 Q2 continues down to the lowest Q2 value of this measurement. The updated global fit that includes the new results yields in this Q2 range an electric (magnetic) form factor ~2% smaller (~1% larger) than the previous global fit. We obtain new extractions of the proton electric and magnetic radii, which are (rE2)1/2 = 0.875 ± 0.010 fm and (rM2)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.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [7] ;  [10] ;  [11] ;  [2] ;  [12] ;  [13] ;  [12] ;  [5] ;  [14] ;  [15] ;  [4] more »;  [3] ;  [7] ;  [7] ;  [16] ;  [4] ;  [5] ;  [17] ;  [13] ;  [7] ;  [18] ;  [19] ;  [3] ;  [20] ;  [7] ;  [8] ;  [19] ;  [21] ;  [22] ;  [7] ;  [7] ;  [23] ;  [8] ;  [24] ;  [25] ;  [25] ;  [26] ;  [27] ;  [28] ;  [29] ;  [18] ;  [4] ;  [6] ;  [8] ;  [30] ;  [7] ;  [15] ;  [31] ;  [18] ;  [8] ;  [32] ;  [25] ;  [33] ;  [34] ;  [35] ;  [36] ;  [8] ;  [23] ;  [20] ;  [37] ;  [7] ;  [38] ;  [39] « less
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  2. Univ. of Kentucky, Lexington, KY (United States)
  3. College of William and Mary, Williamsburg, VA (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
  5. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  6. Florida Intl Univ., Miami, FL (United States)
  7. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  8. Univ. of Virginia, Charlottesville, VA (United States)
  9. Seoul National Univ. (Korea, Republic of)
  10. INFN, Rome (Italy); National Institute of Health, Rome (Italy)
  11. Smith College, Northampton, MA (United States)
  12. INFN, Rome (Italy)
  13. Blaise Pascal Univ., Aubiere (France)
  14. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Rutgers Univ., Piscataway, NJ (United States)
  15. Saint Mary's Univ., Halifax, NS (Canada)
  16. Longwood Univ., Farmville, VA (United States)
  17. Univ. of Regina (Canada)
  18. Rutgers Univ., Piscataway, NJ (United States)
  19. Kent State Univ., Kent, OH (United States)
  20. INFN, Bari (Italy)
  21. California State Univ. (CalState), Long Beach, CA (United States)
  22. NRCN, Beer-Sheva (Israel)
  23. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  24. Saint Norbert College, De Pere, WI (United States)
  25. Tel Aviv Univ., Ramat Aviv (Israel)
  26. Univ. of Glasgow, Scotland (United Kingdom)
  27. Duke Univ., Durham, NC (United States)
  28. Duke Univ., Durham, NC (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  29. Syracuse Univ., NY (United States)
  30. Tel Aviv Univ., Ramat Aviv (Israel); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  31. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Temple Univ., Philadelphia, PA (United States)
  32. Yerevan Physics Inst. (YerPhI) (Armenia)
  33. Inst. Jazef Stefan, Ljubljana (Slovenia); Univ. of Ljubljana (Slovenia)
  34. Argonne National Lab. (ANL), Argonne, IL (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  35. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Temple Univ., Philadelphia, PA (United States)
  36. Univ. of South Carolina, Columbia, SC (United States)
  37. Univ. of Illinois, Urbana-Champaign, IL (United States)
  38. Hampton Univ., Hampton, VA (United States)
  39. Lanzhou Univ. (China)
Publication Date:
OSTI Identifier:
1028726
Report Number(s):
JLAB-PHY--11-1311; DOE/OR/23177--1470; arXiv:1102.0318
Journal ID: ISSN 0370-2693; TRN: US1105609
Grant/Contract Number:
AC05-06OR23177
Type:
Accepted Manuscript
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 705; Journal Issue: 1-2; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ACCURACY; CORRECTIONS; ELECTRON PROBES; ELECTROMAGNETIC FORM FACTORS; ELECTRON-PROTON INTERACTIONS; EXTRACTION; FORM FACTORS; FOUR MOMENTUM TRANSFER; HYDROGEN; LAMB SHIFT; POLARIMETRY; POLARIZATION; PROTONS; RANGE; RECOILS; YIELDS