Magnetic scattering: pairwise little group and pairwise helicity
開始日時 | 2021/01/05 11:00 |
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終了日時 | 2021/01/05 12:00 |
講演者 | Prof. Csaba Csaki ( Cornell University ) |
会場 | Online (Zoom) |
連絡先 | Ryutaro Matsudo / matsudo-AT-post.kek.jp |
言語 | English |
ウェブサイト |
概要
I discuss how to construct a Lorentz-invariant S-matrix for the scattering of electrically and magnetically charged particles. A key ingredient is a revision of our fundamental understanding of multi-particle representations of the Poincare group. Surprisingly, the asymptotic states for electric-magnetic scattering transform with an additional little 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 represents the extra angular momentum stored in the asymptotic electromagnetic field. We define a new kind of pairwise spinor-helicity variable, which 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-monopole 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 partial waves. Our construction provides a significant new achievement for the on-shell program, succeeding where the Lagrangian description has so far failed.