Induced proton polarization for pi^0 electroproduction at Q^2 = 0.126 (GeV/c)^2 around the Delta(1232) resonance
nucl-ex
/ Authors
/ Abstract
We present the first measurement of the induced proton polarization P_n in pi^0 electroproduction on the proton around the Delta resonance. The measurement was made at a central invariant mass and a squared four-momentum transfer of W=1231 MeV and Q^2 = 0.126 (GeV/c)^2, respectively. We measured a large induced polarization, P_n = -0.397 +/- 0.055 +/- 0.009. The data suggest that the scalar background is larger than expected from a recent effective Hamiltonian model.