0000000000739560
AUTHOR
Rolf Tarrach
The Electromagnetic Polarizabilities of the Proton and the Scalar-Isoscalar gamma gamma --> pi pi Amplitude
In a dispersive approach to the calculation of the electromagnetic polarizabilities of the proton, the sensitivity to the annihilation channel input is analyzed. It is shown that the isoscalar s wave absorptive part gives the overwhelming contribution. The connection with the poorly known γγ→ππ amplitude is established and some numerical estimates are presented.
Unsubtracted dispersion-relation for longitudinal compton amplitude
Abstract It is shown that there is a simple connection between the slope, at q2 = 0, of the longitudinal Compton amplitude and the electric polarizability of the nucleon. The longitudinal subtraction function is thus known to order q2. The assumption of an unsubtracted dispersion relation for the longitudinal amplitude leads to a sum rule for the electric polarizability. This is a model independent test of the high-energy behaviour of the forward virtual Compton amplitude.