SCATTERING OFF AN SO(10) COSMIC-STRING

The scattering of fermions from the Abelian string arising during the phase transition SO(10) --> SU(5) x Z(2) induced by the Higgs field in the 126 representation is studied. Elastic cross sections and baryon-number-violating cross sections due to the coupling to gauge fields in the core of the string are computed by both a first-quantized method and a perturbative second-quantized method. The elastic cross sections are found to be Aharonov-Bohm-type. However, there is a marked asymmetry between the scattering cross sections for left- and right-handed fields. The catalysis cross sections are small, depending on the grand unified scale. If cosmic strings were observed our results could help tie down the underlying gauge group.