Semi-leptonic four-fermion final states in polarised γγreactions: Exact results vs an improved narrow width approximation
Abstract
We calculate the process
γγ→
e
−
ν
¯
e
u
d
¯
with the full set of Feynman diagrams. We consider different implementations of the
W
width and different combinations of the photon polarisations. The results of an improved narrow width approximation based on
γγ→
W
+
W
−
with full spin-correlations that takes into account different angular cuts as well as cuts on the invariant masses are compared to those of the complete calculation.