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SUMMARY:Magnetic scattering: pairwise little group and pairwise helicity
DTSTART:20201130T140000
DTEND:20201130T153000
DTSTAMP:20260929T064115Z
UID:4f4b89cbe68ac89c8fc3f2dd871c47c6df4455b243d0202d42e45f1e
CATEGORIES:Conferences - Seminars
DESCRIPTION:Csaba Csaki (Cornell U.)\nI 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 under
 standing of multi-particle representations of the Poincaré group. Surpri
 singly\, the asymptotic states for electric-magnetic scattering transfor
 m with an additional little group phase\, associated with pairs of elec
 trically and magnetically charged particles. I will discuss the general co
 nstruction of such states. The resulting "pairwise helicity" is identifie
 d 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 f
 or electric-magnetic scattering amplitudes. We then construct the most g
 eneral 3-point S-matrix elements\, as well as the full partial wave decomp
 osition for the 2 -> 2 fermion-monopole S-matrix. In particular\, we deriv
 e the famous helicity flip in the lowest partial wave as a simple conseq
 uence of a generalized spin-helicity selection rule\, as well as the full
  angular dependence for the higher partial waves. Our construction provide
 s a significant new achievement for the on-shell program\, succeeding wher
 e the Lagrangian description has so far failed. \n\nRecordings will be av
 ailable at: https://mediaspace.epfl.ch/channel/High+Energy+Theory+Seminar
 s/32518
LOCATION:Zoom https://epfl.zoom.us/j/86370587147
STATUS:CONFIRMED
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