Recoil Polarization for Delta Excitation in Pion Electroproduction

Abstract : We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W=1.23 GeV at Q$^2=1.0 (GeV/c)^2$, obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for $Re(S_1+/M_{1+})=-(6.84\pm 0.15)\%$ and $Re(E_{1+}/M_{1+})=-(2.91\pm0.19)\%$ that are distinctly different from those from the traditional Legendre analysis based upon M$_{1+}$ dominance and $\ell_{\pi} \leq 1$ truncation
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Submitted on : Friday, September 2, 2005 - 3:31:06 PM
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J.J. Kelly, R. E. Roche, Z. Chai, M. K. Jones, O. Gayou, et al.. Recoil Polarization for Delta Excitation in Pion Electroproduction. Physical Review Letters, American Physical Society, 2005, 95, pp.102001(1)-102001(6). ⟨10.1103/PhysRevLett.95.102001⟩. ⟨in2p3-00024528⟩

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