#### Effective field theory approach to soft theorems

- Event time: 1:00pm
- Event date: 11th March 2015
- Speaker: Duff Neill (MIT, Boston)
- Location: Higgs Centre Seminar Room, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

I outline an effective theory approach to the expansion of a gauge theory scattering amplitude in the limit that a participating gluon goes soft. The leading order term in the expansion has a well known universal characterization as simple multiplicative eikonal factor of a lower point scattering amplitude. At subleading orders in the soft expansion, one can find an extended version of the universality at tree level in the loop expansion, known as the Low-Burnett-Kroll theorem, where the multiplicative factor acts as a differential operator on the lower point amplitude. However, at loop level, collinear physics spoils this universality at subleading orders, due to a correlated soft and collinear limit of loop integration. Still, using the tools of effective theory, much of the universality found at leading order can be extended to subleading orders, and a complete characterization of new terms in the factorization can be had. The guiding principles will be the reparametrization invariance of the effective theory, and its construction out of manifestly gauge invariant objects.

The Particle Physics Theory seminar is a weekly series of talks reflecting the diverse interests of the group. Topics include analytic and numerical calculations based on the Standard Model of elementary particle physics, theories exploring new physics, as well as more formal developments in gauge theories and gravity..