Theory seminar (11am): Alessandro Gavardi: Subleading power corrections to the color-singlet transverse momentum spectra

Thursday 5 Jun 2025, 11:00 → 12:00 Europe/Amsterdam

Veltman Centre (Nikhef)

One of the computational bottlenecks in state-of-the-art QCD NNLO calculations matched to resummation is the computation of the non-singular contributions to the spectrum of the given resolution variable (for example, the transverse momentum qT of the color singlet). The analytic knowledge of the spectrum beyond leading power would allow us to approximate such contributions, thus eliminating the need for a numeric subtraction in the small limit of the resolution variable.

In this talk, I will discuss a systematic way to calculate the qT NNLO power corrections within the SCET formalism. I will explicitly show that the naive expectation that soft and collinear regions are sufficient to reproduce their infrared pole structure does not hold beyond leading power. A new class of regions arises, where the partons can have hard momenta if the sum of their transverse momenta is small.

Despite not being plagued by rapidity divergences, these contributions carry infrared poles in the dimensional regulator and thus contribute to the qT logarithmic structure. I will show how to systematically compute them and combine them with the soft and collinear ones to reproduce the power expansion of the qT spectrum.

Gavardi_2025_Nikhef.pdf