Investigation of the conjectured nucleon deformation at low momentum transfer

Authors :: Sparveris, NF Alarcon, R Bernstein, AM Bertozzi, W and Botto, T Bourgeois, P Calarco, J Casagrande, F Distler, MO Dow, K Farkondeh, M Georgakopoulos, S Gilad, S and Hicks, R Holtrop, M Hotta, A Jiang, X Karabarbounis, A and Kirkpatrick, J Kowalski, S Milner, R Miskimen, R and Nakagawa, I Papanicolas, CN Sarty, AJ Sato, Y Sirca, S and Shaw, J Six, E Stave, S Stiliaris, E Tamae, T and Tsentalovich, G Tschalaer, C Turchinetz, W Zhou, ZL and Zwart, T
Publication Year :: 2005
Abstract: We report new precise H(e,e(’)p)pi(0) measurements at the Delta(1232) resonance at Q(2)=0.127 (GeV/c)(2) obtained at the MIT-Bates out-of-plane scattering facility which are particularly sensitive to the transverse electric amplitude (E2) of the gamma(*)N–>Delta transition. The new data have been analyzed together with those of earlier measurements to yield precise quadrupole to dipole amplitude ratios: Re(E-1+(3/2)/M-1+(3/2))=(-2.3+/-0.3(stat+syst)+/-0.6(model))% and Re(S-1+(3/2)/M-1+(3/2))=(-6.1+/-0.2(stat+syst)+/-0.5(model))% for M-1+(3/2)=(41.4+/-0.3(stat+syst)+/-0.4(model))(10(-3)/m(pi)(+)). The derived amplitudes give credence to the conjecture of deformation in hadrons favoring, at low Q(2), the dominance of mesonic effects.