skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Flavor decomposition of the nucleon electromagnetic form factors at low Q 2

Journal Article · · Physical Review. C, Nuclear Physics

Background: The spatial distribution of charge and magnetization within the proton is encoded in the elastic form factors. These have been precisely measured in elastic electron scattering, and the combination of proton and neutron form factors allows for the separation of the up- and down-quark contributions. Purpose: In this work, we extract the proton and neutron form factors from worldwide data with an emphasis on precise new data covering the low-momentum region, which is sensitive to the large-scale structure of the nucleon. From these, we separate the up- and down-quark contributions to the proton form factors. Method: We combine cross section and polarization measurements of elastic electron-proton scattering to separate the proton form factors and two-photon exchange (TPE) contributions. We combine the proton form factors with parametrization of the neutron form factor data and uncertainties to separate the up- and down-quark contributions to the proton's charge and magnetic form factors. Results: The extracted TPE corrections are compared to previous phenomenological extractions, TPE calculations, and direct measurements from the comparison of electron and positron scattering. The flavor-separated form factors are extracted and compared to models of the nucleon structure. Conclusions: With the inclusion of the precise new data, the extracted TPE contributions show a clear change of sign at low Q(2), which is necessary to explain the high-Q(2) form factor discrepancy while being consistent with the known Q(2) -> 0 limit. We find that the new Mainz data yield a significantly different result for the proton magnetic form factor and its flavor-separated contributions. We also observe that the rms radius of both the up- and down-quark distributions are smaller than the rms charge radius of the proton.

Research Organization:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Office of Science - Office of Nuclear Physics
DOE Contract Number:
AC02-06CH11357
OSTI ID:
1392107
Journal Information:
Physical Review. C, Nuclear Physics, Vol. 91, Issue 6; ISSN 0556-2813
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English

References (98)

Two-Photon Exchange and Elastic Electron-Proton Scattering journal October 2003
Two-photon exchange at low Q 2 journal March 2007
Strange-Quark Contributions to Parity-Violating Asymmetries in the Forward G0 Electron-Proton Scattering Experiment journal August 2005
Explanation and prediction of observables using continuum strong QCD journal July 2014
Determination of two-photon exchange amplitudes from elastic electron-proton scattering data journal June 2011
Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to Q 2 = 8.5 GeV 2 journal June 2010
The spin and flavor dependence of parton distribution functions journal September 1988
Empirical parametrization of the two-photon-exchange effect contributions to the electron-proton elastic scattering cross section journal May 2011
Scattering of positrons and electrons from protons journal August 1967
Electromagnetic form factors of the proton at squared four-momentum transfers between 10 and 50 fm−2 journal April 1971
P ARITY -V IOLATING E LECTRON S CATTERING AND N UCLEON S TRUCTURE journal December 2001
New Precision Limit on the Strange Vector Form Factors of the Proton journal March 2012
Backward scattering of positrons and electrons on protons journal January 1968
Publisher's Note: Proton elastic form factor ratios to Q 2 = 3.5 GeV 2 by polarization transfer [Phys. Rev. C 71, 055202 (2005)] journal June 2005
Proton G E / G M from beam-target asymmetry journal September 2006
Comparison of Elastic Positron-Proton and Electron-Proton Scattering Cross Sections journal November 1967
Interpretation of the flavor dependence of nucleon form factors in a generalized parton distribution model journal December 2013
Erratum: Empirical parametrization of the two-photon-exchange effect contributions to the electron-proton elastic scattering cross section [Phys. Rev. C 83 , 054307 (2011)] journal August 2011
How to Reconcile the Rosenbluth and the Polarization Transfer Methods in the Measurement of the Proton Form Factors journal October 2003
Precision Rosenbluth Measurement of the Proton Elastic Form Factors journal April 2005
The ratio of proton electromagnetic form factors via recoil polarimetry at journal January 2006
Search for Effects Beyond the Born Approximation in Polarization Transfer Observables in e p Elastic Scattering journal March 2011
Reexamination of phenomenological two-photon exchange corrections to the proton form factors and e ± p scattering journal November 2011
Two-Photon Exchange in Elastic Electron-Proton Scattering: A QCD Factorization Approach journal August 2009
Measurements of electron-proton elastic cross sections for 0.4 < Q 2 < 5.5 ( GeV c ) 2 journal July 2004
Measurement of the ratio of the proton form factors, GE/GM, at high momentum transfers and the question of scaling journal January 1970
How well do we know the electromagnetic form factors of the proton? journal September 2003
Proton elastic form factor ratios to Q 2 = 3.5 GeV 2 by polarization transfer journal May 2005
Measurements of the proton elastic form factors for 1 Q 2 3 ( G e V / c ) 2 at SLAC journal June 1994
Evidence for two-photon exchange contributions in electron-proton and positron-proton elastic scattering journal March 2004
Comparison of Electron-Proton and Positron-Proton Elastic Scattering at Four-Momentum Transfers up to 5.0 ( G e V / c ) 2 journal August 1968
Polarization Transfer in the He 4 ( e , e p ) H 3 Reaction at Q 2 = 0.8 and 1.3 ( GeV / c ) 2 journal August 2010
Δ Resonance Contribution to Two-Photon Exchange in Electron-Proton Scattering journal October 2005
Measurements of the electric and magnetic form factors of the proton from Q 2 =1.75 to 8.83 (GeV/ c ) 2 journal November 1994
Proton Structure from the Measurement of 2S-2P Transition Frequencies of Muonic Hydrogen journal January 2013
Two-photon exchange in elastic electron-nucleon scattering journal September 2005
Polarization transfer in elastic electron scattering from nucleons and deuterons journal January 1981
Coulomb corrections in the extraction of the proton radius journal October 2013
Partonic Calculation of the Two-Photon Exchange Contribution to Elastic Electron-Proton Scattering at Large Momentum Transfer journal September 2004
Proton Form Factors from Elastic Electron-Proton Scattering journal February 1966
Review of two-photon exchange in electron scattering journal October 2011
Role of diquark correlations and the pion cloud in nucleon elastic form factors journal October 2014
Measurement of G E p / G M p in e p e p to Q 2 = 5.6 GeV 2 journal February 2002
Polarization Transfer in the H e 4 ( e , e p ) H 3 Reaction up to Q 2 = 2.6     ( G e V / c ) 2 journal July 2003
Survey of Nucleon Electromagnetic Form Factors journal March 2009
Measurement of the Two-Photon Exchange Contribution to the Elastic e ± p Scattering Cross Sections at the VEPP-3 Storage Ring journal February 2015
Experimental constraints on nonlinearities induced by two-photon effects in elastic and inelastic Rosenbluth separations journal February 2006
Strange Quark Contributions to Parity-Violating Asymmetries in the Backward Angle G0 Electron Scattering Experiment journal January 2010
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data journal February 2015
Nucleon electromagnetic form factors journal May 2007
Electric and magnetic form factors of the proton journal July 2014
Is there model-independent evidence of the two-photon-exchange effect in the electron–proton elastic scattering cross section? journal September 2007
Strange Vector Form Factors from Parity-Violating Electron Scattering journal May 2011
Two-photon exchange in a dispersion approach journal August 2008
Nucleon electromagnetic form factors journal October 2007
Measurement of the Proton’s Electric to Magnetic Form Factor Ratio from H 1 ( e , e p ) journal January 2007
Positron-Proton Elastic Scattering at 800 and 1200 MeV journal February 1968
High-precision measurement of the proton elastic form factor ratio <mml:math altimg="si1.gif" overflow="scroll" xmlns:xocs="http://www.elsevier.com/xml/xocs/dtd" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.elsevier.com/xml/ja/dtd" xmlns:ja="http://www.elsevier.com/xml/ja/dtd" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:tb="http://www.elsevier.com/xml/common/table/dtd" xmlns:sb="http://www.elsevier.com/xml/common/struct-bib/dtd" xmlns:ce="http://www.elsevier.com/xml/common/dtd" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:cals="http://www.elsevier.com/xml/common/cals/dtd"><mml:msub><mml:mi>μ</mml:mi><mml:mi>p</mml:mi></mml:msub><mml:msub><mml:mi>G</mml:mi><mml:mi>E</mml:mi></mml:msub><mml:mo stretchy="false">/</mml:mo><mml:msub><mml:mi>G</mml:mi><mml:mi>M</mml:mi></mml:msub></mml:math> at low <mml:math altimg="si2.gif" overflow="scroll" xmlns:xocs="http://www.elsevier.com/xml/xocs/dtd" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.elsevier.com/xml/ja/dtd" xmlns:ja="http://www.elsevier.com/xml/ja/dtd" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:tb="http://www.elsevier.com/xml/common/table/dtd" xmlns:sb="http://www.elsevier.com/xml/common/struct-bib/dtd" xmlns:ce="http://www.elsevier.com/xml/common/dtd" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:cals="http://www.elsevier.com/xml/common/cals/dtd"><mml:msup><mml:mi>Q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> journal November 2011
Nucleon quark distributions in a covariant quark–diquark model journal August 2005
Erratum: Comparison of Polarization Observables in Electron Scattering from the Proton and Deuteron [Phys. Rev. Lett. 80, 452 (1998)] journal March 1999
Positron-Proton Scattering journal August 1965
Comparison of Polarization Observables in Electron Scattering from the Proton and Deuteron journal January 1998
Charge symmetry, quarks and mesons journal October 1990
Simple parametrization of nucleon form factors journal December 2004
Two-photon exchange amplitudes for elastic e p scattering at Q 2 = 2.5 GeV 2 from experimental data journal March 2011
Implications of the discrepancy between proton form factor measurements journal February 2004
Low- Q 2 measurements of the proton form factor ratio μ p G E / G M journal November 2011
Scattering of Positrons and Electrons from Protons journal August 1966
Phenomenological analysis of two-photon exchange effects in proton form factor measurements journal August 2007
Measurements of the elastic electromagnetic form factor ratio μ p G Ep / G Mp via polarization transfer journal August 2001
Demonstration of a novel technique to measure two-photon exchange effects in elastic e ± p scattering journal August 2013
Two-Photon Physics in Hadronic Processes journal November 2007
Nucleon form factors and spin content in a quark-diquark model with a pion cloud journal July 2012
Precise Determination of the Strangeness Magnetic Moment of the Nucleon journal June 2005
Box diagram in the elastic electron-proton scattering journal December 2006
High Energy Elastic Scattering of Electrons on Protons journal August 1950
Scattering of High-Energy Positrons from Protons journal November 1962
Electromagnetic form factors of the nucleon: New fit and analysis of uncertainties journal June 2009
Realistic transverse images of the proton charge and magnetization densities journal January 2011
Parity-violating electroweak asymmetry in e p scattering journal June 2004
Extended Gari-Krümpelmann model fits to nucleon electromagnetic form factors journal August 2001
The size of the proton journal July 2010
The Coulomb Scattering of Relativistic Electrons by Nuclei journal December 1948
Nucleon and Roper electromagnetic elastic and transition form factors journal February 2012
Pion Distribution Amplitude from Lattice QCD journal August 2013
Scattering of Polarized Leptons at High Energy journal January 1969
Flavor Decomposition of the Elastic Nucleon Electromagnetic Form Factors journal June 2011
Coulomb distortion in high- Q 2 elastic e p scattering journal August 2004
Global analysis of proton elastic form factor data with two-photon exchange corrections journal September 2007
Flavor decomposition of the nucleon electromagnetic form factors journal December 2012
Aspects of hadron physics journal January 2007
Measurement of proton and neutron electromagnetic form factors at squared four-momentum transfers up to 3 (GeV/c)2 journal July 1973
Revealing Dressed Quarks via the Proton’s Charge Distribution journal September 2013
Extraction of two-photon contributions to the proton form factors journal January 2005
Final analysis of proton form factor ratio data at Q 2 = 4.0 , 4.8, and 5.6 GeV 2 journal April 2012
Measurement of GEp/GMp via polarization transfer at Q2 = 0.4 GeV /c2 journal September 2001
Model-independent properties of two-photon exchange in elastic electron-proton scattering journal November 2004
Parity-Violating Electron Scattering and the Electric and Magnetic Strange Form Factors of the Nucleon journal November 2012

Similar Records

Related Subjects