HET Journal club: Andrea Marzolla

(Note unusual location: Bk2 in basement of NBIA)

Speaker: Andrea Marzolla (ULB Brussels)

Title: Poincaré symmetry shapes the massive 3-point amplitude

Abstract: 

Poincaré invariance imposes strong non-perturbative constraints on the dependence of scattering amplitudes on the kinematical variables in 4-dimensional Minkowski spacetime. For massless external states, Benincasa and Cachazo have shown that the 3-point amplitude is fully determined up to a constant (the coupling). We extend their approach, based on the spinor-helicity formalism, to time-like momenta, and we find that the functional form of the 3-point amplitude, also when it involves massive external states, is fully determined, up to (several) constants.

In this talk I review the derivation in the massless case, enlightening the role of the little group covariance of the amplitude in constraining its functional form, and the particularly simple form that these constraints get in the spinor-helicity language. Then I will show how to extend these procedure to the massive case, deriving the constraining equations for the massive little group, and eventually showing the expressions for 3-point amplitudes involving one, two, or three massive particles.