Cross sections and beam asymmetries for $$\vev{e}p \to en\pi^+$$ in the nucleon resonance region for $$1.7 \le Q^2 \le 4.5 (GeV)^2$$
The exclusive electroproduction process $$\vec{e}p \to e^\prime n \pi^+$$ was measured in the range of the photon virtuality $$Q^2 = 1.7 - 4.5 \rm{GeV^2}$$, and the invariant mass range for the $$n\pi^+$$ system of $$W = 1.15 - 1.7 \rm{GeV}$$ using the CEBAF Large Acceptance Spectrometer. For the first time, these kinematics are probed in exclusive $$\pi^+$$ production from protons with nearly full coverage in the azimuthal and polar angles of the $$n\pi^+$$ center-of-mass system. The $$n\pi^+$$ channel has particular sensitivity to the isospin 1/2 excited nucleon states, and together with the $$p\pi^0$$ final state will serve to determine the transition form factors of a large number of resonances. The largest discrepancy between these results and present modes was seen in the $$\sigma_{LT'}$$ structure function. In this experiment, 31,295 cross section and 4,184 asymmetry data points were measured. Because of the large volume of data, only a reduced set of structure functions and Legendre polynomial moments can be presented that are obtained in model-independent fits to the differential cross sections.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE - Office of Energy Research (ER)
- DOE Contract Number:
- AC05-06OR23177
- OSTI ID:
- 915083
- Report Number(s):
- JLAB-PHY-07-720; DOE/OR/23177-0143; arXiv:0709.1946; TRN: US0804889
- Journal Information:
- Phys.Rev.C, Vol. 77, Issue 1
- Country of Publication:
- United States
- Language:
- English
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