Missing final state puzzle in monopole-fermion scattering

by Ryutaro Matsudo (KEK)


It has been known that when a charged fermion scatters off a monopole, the fermion in the s-wave component must flip its helicity. Because of this  feature, if there are two or more Dirac flavors of massless fermions, any superposition of the fermion states cannot be the final state of the s-wave scattering as it is forbidden by conservation of the electric and flavor charges. The unitary evolution of the state vector, on the other hand, requires some interpretation of the final states. We solve this puzzle by finding new particle excitations in the monopole background, where multi-fermion operators exhibit condensation. The particles are described as excitations of closed-string configurations of the condensates.