Flavor dependent $b$-profiles from Drell-Yan spectra at low transverse momenta

We discuss our recent study of the impact of collinear PDFs and their uncertainties on the determination of transverse momentum dependent (TMD) distributions and the description of Drell-Yan (DY) production measurements at low transverse momenta. Using QCD factorization and evolution in transverse coordinate $b$ space, this study takes into account for the first time flavor-dependent non-perturbative $b$-profiles. It illustrates that collinear PDF uncertainties and non-perturbative TMD flavor dependence are both essential to obtain reliable TMD determinations.