Separated Response Function Ratios in Exclusive, Forward pi^{+/-} Electroproduction

Abstract

The study of exclusive ${\pi }^{\pm }$ electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio $R_L={\sigma }_L^{{\pi }^{-}}/{\sigma }_L^{{\pi }^{+}}$ 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 $R_T={\sigma }_T^{{\pi }^{-}}/{\sigma }_T^{{\pi }^{+}}$ 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 ${\pi }^{\pm }$ electroproduction on the deuteron at central $Q^2$ values of 0.6, 1.0, 1.6 GeV${}^2$ at $W$=1.95 GeV, and $Q^2=2.45$ GeV${}^2$ at $W$=2.22 GeV. Here, we present the $L$ and $T$ cross sections, with emphasis on $R_L$ and $R_T$, and compare them with theoretical calculations. Results for the separated ratio $R_L$ indicate dominance of the pion-pole diagram at low $-t$, while results for $R_T$ are consistent with a transition between pion knockout and quark knockout mechanisms.

6 pages, 3 figures

References in corpus (4)

• Determination of the Charged Pion Form Factor at Q2=1.60 and 2.45 (GeV/c)2
• Charged pion form factor between Q^2=0.60 and 2.45 GeV^2. II. Determination of, and results for, the pion form factor
• Charged pion form factor between $Q^2$=0.60 and 2.45 GeV${}^2$. I. Measurements of the cross section for the ${}^1$H($e,e^{\prime }{\pi }^{+}$)$n$ reaction
• Nucleon Tensor Charge from Exclusive ${\pi }^o$ Electroproduction

Cited by in corpus (1)

• Separated Response Functions in Exclusive, Forward ${\pi }^{\pm }$ Electroproduction on Deuterium