素粒子論セミナーのお知らせ

For over 40 years, scattering of charged fermions off of a magnetic monopole has puzzled us. For some initial states, the final state seems to possess fractional particle numbers (aka "semitons"), but there are no such states in the Fock space of a 4d QFT (hence "unitarity" problem). By a concrete calculation in Polchinski's "fermion-rotor system," an accurate effective theory of monopolefermion scattering, I will show how this puzzle is resolved. The calculation reveals that the processes traditionally thought of as involving semitons do not undergo any scattering at all, while the traditional results without semitons are correct as they are. This finding can impact the experimental bounds on monopole abundance as the most stringent bounds have been based on the traditional analyses.