Heavy quarks (bottom and charm) are ideal to study the hadronization process because they serve as a static color source coupling to the light degrees of freedom. In this talk, I will discuss transverse momentum-dependent (TMD) fragmentation functions (FFs) for heavy quarks and their factorization in terms of novel nonperturbative matrix elements in heavy-quark effective theory (HQET). In this context, I will discuss new TMD sum rules that arise from heavy-quark spin symmetry. Moreover, I will present next-to-leading-order results for the partonic unpolarized heavy-quark TMD FF, a Wilson coefficient that we also expect to appear in other contexts, such as energy-energy correlators measured on heavy quarks or the extension of fixed-order subtraction methods to quasi-collinear limits. Additionally, I will discuss TMD parton distribution functions (PDFs) for the production of heavy quarks from polarized gluons within the nucleon. These new results allow for phenomenological studies of heavy-quark TMD FFs and PDFs at B factories, within jets at the LHC, and in semi-inclusive DIS at the future EIC.
Ankita Budhraja, Juraj Klaric, Johannes Michel, Tanjona R. Rabemananjara