Alladi Ramakrishnan Hall

The eikonal approximation and beyond

Prof. Eric Laenen

NIKHEF

The eikonal, or soft, approximation has a long history in physics,
from ray optics to present-day LHC scattering, when low-energy gluons are radiated.
I review its origin, how it works, and show insights that have emerged from it,
some involving all-order summation of the QCD perturbation series. Then
I discuss the next-to-soft approximation and show patterns we recently
discovered that suggest also these corrections can be predicted from
lower orders.