BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Csaba Csaki (Cornell University) DTSTART:20210217T170000Z DTEND:20210217T180000Z DTSTAMP:20260423T022808Z UID:CMU-TP/24 DESCRIPTION:Title: Magnetic scattering: pairwise little group and pairwise helicity\nby C saba Csaki (Cornell University) as part of Carnegie Mellon theoretical phy sics\n\n\nAbstract\nI discuss how to construct a Lorentz-invariant S-matri x for the scattering of electrically and magnetically charged particles. A key ingredient is a revision of our fundamental understanding of multi-pa rticle representations of the Poincaré group. Surprisingly\, the asymptot ic states for electric-magnetic scattering transform with an additional li ttle group phase\, associated with pairs of electrically and magnetically charged particles. I will discuss the general construction of such states. The resulting "pairwise helicity" is identified with the quantized "cross product" of charges e1 g2- e2 g1 for every charge-monopole pair\, and re presents the extra angular momentum stored in the asymptotic electromagnet ic field. We define a new kind of pairwise spinor-helicity variable\, whic h serves as an additional building block for electric-magnetic scattering amplitudes. We then construct the most general 3-point S-matrix elements\, as well as the full partial wave decomposition for the 2 -> 2 fermion-mon opole S-matrix. In particular\, we derive the famous helicity flip in the lowest partial wave as a simple consequence of a generalized spin-helicity selection rule\, as well as the full angular dependence for the higher pa rtial waves. Our construction provides a significant new achievement for t he on-shell program\, succeeding where the Lagrangian description has so f ar failed.\n LOCATION:https://researchseminars.org/talk/CMU-TP/24/ END:VEVENT END:VCALENDAR