Results 1 
2 of
2
Soft theorems from effective field theory
, 2015
"... The singular limits of massless gauge theory amplitudes are described by an effective theory, called softcollinear effective theory (SCET), which has been applied most successfully to make allorders predictions for observables in collider physics and weak decays. At treelevel, the emission of a ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
The singular limits of massless gauge theory amplitudes are described by an effective theory, called softcollinear effective theory (SCET), which has been applied most successfully to make allorders predictions for observables in collider physics and weak decays. At treelevel, the emission of a soft gauge boson at subleading order in its energy is given by the LowBurnettKroll theorem, with the angular momentum operator acting on a lowerpoint amplitude. For well separated particles at treelevel, we prove the LowBurnettKroll theorem using matrix elements of subleading SCET Lagrangian and operator insertions which are individually gauge invariant. These contributions are uniquely determined by gauge invariance and the reparametrization invariance (RPI) symmetry of SCET. RPI in SCET is connected to the infinitedimensional asymptotic symmetries of the Smatrix. The LowBurnettKroll theorem is generically spoiled by onshell corrections, including collinear loops and collinear emissions. We demonstrate this explicitly both at treelevel and at oneloop. The effective theory correctly describes these configurations, and we generalize the LowBurnettKroll theorem into a new oneloop subleading soft theorem for amplitudes. Our analysis is presented in a manner that illustrates the wider utility of using effective theory techniques to understand the perturbative Smatrix.