arXiv reference

It took almost one year to make this extraction. I am proud that it is finally on arXiv. It is a real achievement to describe so many and so different experiments simultaneously. It requires all parts of the construction to work together and to work properly. There are still issues, but all of the minor issues and should not influence the general picture to much. I am sure; we will fix them eventually.

Abstract: We evaluate the light-cone operator product expansion for the unpolarized transverse momentum dependent (TMD) operator in the background-field technique up twist-3 inclusively. The next-to-leading order (NLO) matching coefficient for the Sivers function is derived. The method, as well as many details of the calculation, are presented.

The abstract is short, but the work is not! In fact, it is the first calculation of such kind in physics of TMDs, and in this article, we look at many aspects of TMD distributions from a different perspective. Due to it I specially made the article as simple and pedagogical as I could. You even can find it boring in some places, but you can also give it to your students (well... master students). Here is arXiv-reference. I have also added working notes on it to supplementary materials (entry 8).

We calculate the matching of the transversity and pretzelosity transverse momentum dependent distributions (TMD) on transversity collinear distribution at the next-to-next-to-leading order (NNLO). We find that the matching coefficient for pretzelosity distribution is zero, despite the matrix element for it is nontrivial. This result suggests that the pretzelosity matches a twist-4 distribution. The matching for transversity TMD distributions is provided for both parton distribution functions and fragmentation functions cases.

arXiv:1805.07243

The files with the result of calculation can be also found here.

We derive the leading order matching of the quark generated polarized transverse momentum dependent (TMD) distributions onto the collinear functions at small values of the transverse distance. Starting from the very definition of the TMD operator and performing the light-cone operator product expansion up to twist-3 order, we evaluate each distribution directly in position space. We primarily consider the cases of Sivers, Boer-Mulders and worm-gear functions. The effects of the TMD process dependence on the matching are explicitly shown. We also discuss the moments of TMD distributions which can be relevant for lattice calculations.

arXiv:1804.08148

In this paper  we look at the consequences of the double-carelessness of the TMD evolution. Strange, but it has been not discussed in the literature at all. In particular, we have shown that due to fact that evolution happens in a 2-dimensional plane, there are infinitely many equivalent solutions. The traditional one, aka "the Sudakov exponent", is not the most convenient. For practical applications we suggest another one that is much much simpler (it is given by an algebraic function).

arXiv: 1803.11089

See also my talk in Pavia.