B. Strandberg

Measurement of the π0→e+e-γ Dalitz decay at the Mainz Microtron

The Dalitz decay pi(0) -> e(+) e(-) gamma has been measured in the gamma p -> pi(0) p reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the pi(0) electromagnetic transition form factor, a(pi) = 0.030 +/- 0.010(tot), is in agreement with existing measurements of this decay and with recent theoretical calculations. The uncertainty obtained in the value of a(pi) is lower than in previous results based on the pi(0) -> e(+) e(-) gamma decay.

Determination of the scalar polarizabilities of the proton using beam asymmetry

Abstract.The scalar dipole polarizabilities,

\Sigma_{3}

\alpha_{E1}

in Compton scattering

αE1 and

Elastic Compton scattering from 3He and the role of the Delta

\beta_{M1}

Photon asymmetry measurements of

βM1, are fundamental properties related to the internal dynamics of the nucleon. The currently accepted values of the proton polarizabilities were determined by fitting to unpolarized proton Compton scattering cross section data. The measurement of the beam asymmetry

\overrightarrow{\gamma} \mathrm{p} \rightarrow \pi^{0} \mathrm{p}

\Sigma_{3}

for E

Σ3 in a certain kinematical range provides an alternative approach to the extraction of the scalar polarizabilities. At the Mainz Microtron (MAMI) the beam asymmetry was measured for Compton scattering below pion photoproduction threshold for the first time. The results are compared with model calculations and the influence of the experimental data on the extraction of the scalar polarizabilities is determined.

_{\gamma}

Abstract.We report observables for elastic Compton scattering from 3He in Chiral Effective Field Theory with an explicit

=320

\Delta(1232)