J. Tonnison, A. M. Sandorfi, S. Hoblit, A. M. Nathan
Published 1998-01-06, updated 1998-03-16Version 3
A proton spin-polarizability characterizing backward Compton scattering has been extracted from a dispersion analysis of data between 33 and 309 MeV. This backward spin-polarizability, "delta" = 27.1 +/-2.2(stat+sys) +2.8/-2.4(model) in units of 10^-4 fm^4, differs significantly from theoretical estimates which are dominated by pi0 t-channel exchange, and indicates a new contribution from the non-perturbative spin-structure of the proton. This new value for "delta" removes an apparent inconsistency in the difference of charge polarizabilities extracted from data above pi-threshold. Our global result, alpha-beta = 10.11 +/-1.74(stat+sys) +1.22/-0.86 (model) in units of 10^-4 fm^3, is consistent with the previous world average of data below 155 MeV. Our value for alpha+beta = 13.23 +/-0.86(stat+sys) +0.20/-0.49(model) is consistent with a recent re-evaluation of the Baldin sum rule.
Comments: Small corrections to LEGS data incorporated; fits recalculated; Tables and Figures updated
Journal: Phys.Rev.Lett. 80 (1998) 4382-4385
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A new evaluation of the Baldin sum rule
First extraction of proton mass radius and scattering length $\left|α_{ρ^0 p}\right|$ from $ρ^0$ photoproduction
