Measurement of the Polarized Structure Function $\ddot{I}{ƒ}_{L{T}^{\prime }}$ for Pion Electroproduction in the Roper Resonance Region

Abstract

The polarized longitudinal-transverse structure function $\ddot{I}{ƒ}_{L{T}^{\prime }}$ measures the interference between real and imaginary amplitudes in pion electroproduction and can be used to probe the coupling between resonant and non-resonant processes. We report new measurements of $\ddot{I}{ƒ}_{L{T}^{\prime }}$ in the $N(1440){1/2}^{+}$ (Roper) resonance region at $Q^2=0.40$ and 0.65 GeV${}^2$ for both the $\ddot{I}{€}^{0}p$ and $\ddot{I}{€}^{+}n$ channels. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at a beam energy of 1.515 GeV. Complete angular distributions were obtained and are compared to recent phenomenological models. The $\ddot{I}{ƒ}_{L{T}^{\prime }}(\ddot{I}{€}^{+}n)$ channel shows a large sensitivity to the Roper resonance multipoles $M_{1-}$ and $S_{1-}$ and provides new constraints on models of resonance formation.

5 pages, 3 figures. Revised manuscript accepted by Physical Review C (Brief Report)