Speaker
Description
The transverse momentum dependent and collinear factorization theorems are independent approaches to the description of scattering cross-sections at high energy. They operate with different set of universal distributions, namely, the transverse momentum distributions (TMDs) and collinear distributions. However, these distributions are not entire independent. In the regime of large transverse momentum or small-$b$ (where $b$ is a Fourier conjugated parameter to the transverse momentum), TMDs can be factorized in the terms of collinear distributions. This relation is often refereed as ``matching relation'', and is a consequence of operator product expansion. In this talk, I will present the small-b expansion for the Sivers, Boer-Mulders, worm-gear-T and worm-gear-L functions, up to next-to-leading order (NLO).
The majority of TMDs match the collinear distributions at higher twists. For that reason their consideration is cumbersome.
The usage of the matching relation is very important for the phenomenology. It allows to incorporate the already known functions into TMDs, and in this way, reduces the parametric freedom of TMD.
| speaker affiliation | University of Regensburg |
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