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Title: Separated Response Function Ratios in Exclusive, Forward π± Electroproduction

The study of exclusive π{sup ±} electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio R{sub L}=σ{sup π{sup -}}{sub L}/σ{sup π{sup +}}{sub 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{sub T}=σ{sup π{sup -}}{sub T}/σ{sup π{sup +}}{sub T} 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 pQCD 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± electroproduction on the deuteron at central Q{sup 2} values of 0.6, 1.0, 1.6 GeV{sup 2} at W=1.95 GeV, and Q{sup 2}=2.45 GeV{sup 2} at W=2.22 GeV. Here, we present the L and T cross sections, with emphasis on R{sub L} and R{sub T}, and compare them with theoretical calculations. Results for the separated ratio RL indicate dominance of the pion-polemore » diagram at low -t, while results for R{sub T} are consistent with a transition between pion knockout and quark knockout mechanisms.« less
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Publication Date:
OSTI Identifier:
1130751
Report Number(s):
JLAB-PHY-14-1868; DOE/OR/23177-3057; arXiv:1404.3985
Journal ID: ISSN 0031-9007; PRLTAO
DOE Contract Number:
AC05-84ER40150; AC05-06OR23177
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 112; Journal Issue: 18
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Energy Research (ER)
Contributing Orgs:
Jefferson Lab F_{π} Collaboration
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS