Description
The electric απ and magnetic βπ charged pion Compton polarizabilities provide stringent tests of Chiral Perturbation Theory. The combination (απ-βπ) was measured at CERN COMPASS via radiative pion Primakoff scattering (Bremsstrahlung of 190 GeV/c π-s) in the nuclear Coulomb field: π + Z → π + γ + Z. This reaction is identified experimentally by virtue of the very small momentum transfer to the target nucleus; and is equivalent to γ + π → γ + π Compton scattering for laboratory γ's of order 1 GeV/c incident on a target pion at rest. COMPASS data analysis (assuming απ+βπ=0 based on theory) gives a preliminary value of απ = -βπ = (1.9±0.7stat.±0.8syst.)×10-4 fm3.
Author
Prof.
Murray Moinester
(Tel Aviv University)
