Measurement of the polarized structure function σLT′ for pion electroproduction in the Roper-resonance region -: art. no. 058202

The polarized longitudinal-transverse structure function sigma(')(LT) measures the interference between real and imaginary amplitudes in pion electroproduction and can be used to probe the coupling between resonant and nonresonant processes. We report new measurements of sigma(')(LT) in the N(1440)1/2(+) (Roper) resonance region at Q(2)=0.40 and 0.65GeV(2) for both the pi(0)p and pi(+)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 sigma(')(LT)(pi(+)n) channel shows a large sensitivity to the Roper-resonance multipoles M1- and S1- and provides new constraints on models of resonance formation.