Exclusive π- Electro-Production From the Neutron in the Resonance Region

Abstract

The study of baryon resonances is crucial to our understanding of nucleon structure. Although the excited states of the proton have been studied in great detail, there are very few data available for the neutron resonances because of the difficulty inherent in obtaining a free neutron target. To overcome this limitation, the spectator tagging technique was used in one of the CEBAF Large Acceptance Spectrometer (CLAS) collaboration experiments, Barely off-shell Nuclear Structure (BoNuS), in Hall-B at Jefferson Lab. We have constructed a radial time projection chamber (RTPC) based on the gaseous electron multiplier (GEM) technology to detect low momentum recoil protons. Electron scattering data were taken in Fall 2005 with beam energies of 2.1, 4.2 and 5.3 GeV using a 7 atmosphere gaseous deuterium target in conjunction with the RTPC and CLAS detectors. We have studied the exclusive reactions D(e, e'π− PCLAS)P and D(e, e'π− PRTPC)P, in which the proton was detected either in CLAS or in the RTPC. Measurements of the absolute differential cross section over a large kinematic range are reported.