Empirical parametrization of the two-photon-exchange effect contributions to the electron-proton elastic scattering cross section

Journal Article · Sun May 15 00:00:00 EDT 2011 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.83.054307· OSTI ID:21502454

Qattan, I A ^[1]; Alsaad, A ^[2]

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1. Khalifa University of Science, Technology and Research, P.O. Box 573, Sharjah (United Arab Emirates)
2. Jordan University of Science and Technology, Department of Physical Sciences, P.O. Box 3030, Irbid 22110 (Jordan)

The most recent electron-proton elastic scattering data were re-analyzed using an empirical parametrization of the two-photon-exchange (TPE) effect contributions to {sigma}{sub R}. The TPE effect contribution F(Q{sup 2},{epsilon}) was double Taylor series expanded as a polynomial of order n keeping only terms linear in {epsilon} to account for the experimentally observed and verified linearity of the Rosenbluth plots. We fix the ratio R=G{sub Ep}/G{sub Mp} to be that obtained from a fit to the recoil-polarization data and parametrize {sigma}{sub R} first by a three-parameter formula (fit I) and then by a two-parameter formula (fit III). In contrast to previous analyses, the fit parameter G{sub Mp}{sup 2} as obtained from these fits is either smaller or equal to the values obtained from our conventional Rosenbluth fit (fit II) but never larger. The ratio g(Q{sup 2})/G{sub Mp}{sup 2} which represents the ratio of the TPE and one-photon-exchange (OPE) effect contributions to the intercept of {sigma}{sub R} is large and it ranges 3%-88%. The ratio R{sub 1{gamma}x2{gamma}={tau}}f(Q{sup 2})/G{sub Ep}{sup 2} which represents the ratio of the TPE and OPE effect contributions to the slope of {sigma}{sub R} is also large, reaching a value of 12.0-14.4 at Q{sup 2}= 5.25 (GeV/c){sup 2}. The ratio R{sub 1{gamma}x2{gamma}} as obtained from fits I and III is consistent, within error, with those obtained from previous analyses. Our formulas seem to explain the linearity of {sigma}{sub R}. Moreover, our analysis shows that the extracted G{sub Ep}{sup 2} and G{sub Mp}{sup 2} using the conventional Rosenbluth separation method can in fact be broken into the usual OPE and TPE contributions. Therefore, {sigma}{sub R} can in fact be derived under weaker conditions than those imposed by the Born approximation. Our results show that the TPE amplitudes, g(Q{sup 2})/G{sub Mp}{sup 2} and f(Q{sup 2})/G{sub Mp}{sup 2}, are sizable and grow with Q{sup 2} value up to Q{sup 2}{approx}6 (GeV/c){sup 2} in agreement with previous studies. A revision of and comparison to previous analyses are also presented.

• OSTI ID: 21502454
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 83, Issue 5; Other Information: DOI: 10.1103/PhysRevC.83.054307; (c) 2011 American Institute of Physics; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
BORN APPROXIMATION
COMPARATIVE EVALUATIONS
CROSS SECTIONS
ELASTIC SCATTERING
ELECTRON-PROTON INTERACTIONS
ELECTRONS
GEV RANGE
PHOTONS
POLARIZATION
POLYNOMIALS
PROTONS
RECOILS
APPROXIMATIONS
BARYONS
BOSONS
CALCULATION METHODS
ELECTRON-NUCLEON INTERACTIONS
ELEMENTARY PARTICLES
ENERGY RANGE
EVALUATION
FERMIONS
FUNCTIONS
HADRONS
INTERACTIONS
LEPTON-BARYON INTERACTIONS
LEPTON-HADRON INTERACTIONS
LEPTON-NUCLEON INTERACTIONS
LEPTONS
MASSLESS PARTICLES
NUCLEONS
PARTICLE INTERACTIONS
SCATTERING