Evidence for a small component of circular polarization in relativistic electron bremsstrahlung
Using a transmission type polarimeter, an asymmetry has been found that can be ascribed to a circularly polarized component in the bremsstrahlung beam of unpolarized relativistic electrons from the Mainz electron linac, in the region of electron energiesEel between 140 and 400 MeV. The experiment is described in detail. Systematical errors are discussed. For a comparison with electroweak theory, an exact calculation for small photon emission angles (of the order ofm c2/Eel) is needed.
We give a brief introduction to the study of the algebraic structures -- and their geometrical interpretations -- which arise in the BRST construction of a conformal string background. Starting from the chiral algebra $\cA$ of a string background, we consider a number of elementary but universal operations on the chiral algebra. From these operations we deduce a certain fundamental odd Poisson structure, known as a Gerstenhaber algebra, on the BRST cohomology of $\cA$. For the 2D string background, the correponding G-algebra can be partially described in term of a geometrical G-algebra of the affine plane $\bC^2$. This paper will appear in the proceedings of {\it Strings 95}.