Separated Response Function Ratios in Exclusive, Forward π[superscript ±] Electroproduction
Name
PhysRevLett.112.182501.pdf
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286.29 KB
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Author(s)
Huber, G. M.
Blok, H. P.
Butuceanu, C.
Gaskell, D.
Horn, T.
Mack, D. J.
Abbott, D.
Aniol, K.
Anklin, H.
Armstrong, C.
Date Issued
May 2014
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Huber, G. M., et al. "Separated Response Function Ratios in Exclusive, Forward π[superscript ±] Electroproduction." Phys. Rev. Lett. 112 (May 2014), 182501. © 2014 American Physical Society
Version
Final published version
Abstract
The study of exclusive π[superscript ±] electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio R[subscript L] = σ[π− over L]/σ[π+ over L] is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of R[subscript T] = σ[π− over L]/σ[π+ over L] from unity at small −t, to 1/4 at large −t, would suggest a transition from coupling to a (virtual) pion to coupling to individual quarks. Furthermore, the mentioned ratios may show an earlier approach to perturbative QCD than the individual cross sections. We have performed the first complete separation of the four unpolarized electromagnetic structure functions above the dominant resonances in forward, exclusive π[superscript ±] electroproduction on the deuteron at central Q[superscript 2] values of 0.6, 1.0, 1.6 GeV[ superscript 2] at W = 1.95 GeV, and Q[superscript 2] = 2.45 GeV[superscript 2] at W=2.22 GeV. Here, we present the L and T cross sections, with emphasis on R[subscript L] and R[subscript T], and compare them with theoretical calculations. Results for the separated ratio R[subscript L] indicate dominance of the pion-pole diagram at low −t, while results for R[subscript T] are consistent with a transition between pion knockout and quark knockout mechanisms.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1103/PhysRevLett.112.182501
