N ->Delta transition and proton polarizabilities from measurements of p((gamma)over-right-arrow,gamma), p((gamma)over-right-arrow,pi(0)), and p((gamma)over-right-arrow,pi(+)) - art. no. 025203

We report new high-precision measurements of p(<(<gamma>)over right arrow>, gamma), p(<(<gamma>)over right arrow>,pi (o)) and p(<(<gamma>)over right ar row>,pi (+)) cross section and beam asymmetry angular distributions for pho ton beam energies in the range from 213 MeV to 333 MeV. The cross sections for all three channels are locked together with a small common systematic s cale uncertainty of 2%. A large overdetermination of kinematic parameters w as used to achieve the first complete separation of the Compton scattering and pi (o)-production channels. This has also allowed all detector efficien cies for the p(<(<gamma>)over right arrow>,gamma) and p(<(<gamma>)over righ t arrow>,pi (o)) channels to be measured directly from the data itself with out resorting to simulations. The new Compton results are approximately 30% higher than previous Bonn data near the peak of the Delta resonance, resol ving a long-standing unitarity puzzle. However, our p(<(<gamma>)over right arrow>,pi (o)) and p(<(<gamma>)over right arrow>,pi (+)) cross sections are also about 10% higher than both earlier Bonn data and recent Mainz measure ments, while our p(<(<gamma>)over right arrow>,pi (+)) cross sections are i n good agreement with results from Tokyo. Our polarization asymmetry data a re of the highest precision yet available and have considerable impact upon multipole analyses. These new data have been combined with other polarizat ion ratios in a simultaneous analysis of both Compton scattering and pi pro duction, with Compton scattering providing two new constraints on the photo pion amplitude, This analysis has improved the accuracy in the E2/M1 mixing ratio for the N-->Delta transition, EMR = -[3.07+/-0.26(stat+syst)+/-0.24( model)](%), and the corresponding N-->Delta transverse helicity amplitudes, A(1/2)= -[135.7+/-1.3(stat+syst) +/- 3.7(model)](10(-3) GeV-1/2) and A(3/2 )=-[266.9+/-1.6(stat+syst) +/-7.8(model)](10(-3) GeV-1/2). From these we de duce an oblate spectroscopic deformation for the Delta (+). The same simult aneous analysis has been used to extract the proton dipole polarizabilities , <(<alpha>)over bar>-<(<beta>)over bar>= +[10.39 +/- 1.77( stat + syst) (1.02)(-1.87)(model)](10(-4) fm(3)) in agreement with previous low energy me asurements, and <(<alpha>)over bar>+<(<beta>)over bar>=+[13.25+/-0.86(statsyst) (+0.23)(-0.58)(model)](10(-4) fm(3)) in agreement with recent evaluat ions of the Baldin sum rule. Our simultaneous analysis has also provided th e first determination of the proton spin polarizabilities, gamma (pi)=-[27. 23+/-2.27(stat+syst) (+2,24)(-2.10) (model)](10(-4) fm(4)), gamma (o)=-[1.5 5 +/-0.15(stat+syst) (+0.03)(-0.03)(model)](10(-4) fm(4)) gamma (13) = + [3 .94 +/- 0.53(stat + syst) (+0.20)(-0.18)(model)](10(-4) fm(4)), and gamma ( 14) = -[2.20 +/- 0.27(stat + syst) (+0.05)(-0.09)(model)](10(-4) fm(4)). Th e extracted value of the backward spin polarizability, gamma (pi) is consid erably different from other analyses and this has been instrumental in brin ging the value of <(<alpha>)over bar> - <(<beta>)over bar> extracted from h igh energy data into agreement with low energy experiments.