Measurement of electric and magnetic polarizabilities with Primakoff reaction at COMPASS

The COMPASS spectrometer is well suited to perform precise measurements of the pion polarizabilities via the Primakoff reaction $\pi(Z,A)\rightarrow\pi+(Z,A)+\psi$. The electric ($\bar{\alpha}_{\pi}$) and magnetic ($\bar{\beta}_{\pi}$) polarizabilities characterize the response of the response of the pion quark substructure to the electromagnetic field of the $\psi$ during the $\pi\psi$ scattering. The results of a simulation for the foreseen 2004 setup are presented. The measurement of the pion polarizabilities allows for a test of the chiral perturbation theory ($_{X}PT$) predictions.