The Sivers transverse single spin asymmetry (TSSA) is calculated and compared
at different scales using the TMD evolution equations applied to previously
existing extractions. We apply the Collins-Soper-Sterman (CSS) formalism, using
the version recently developed by Collins. Our calculations rely on the
universality properties of TMD-functions that follow from the TMD-factorization
theorem. Accordingly, the non-perturbative input is fixed by earlier
experimental measurements, including both polarized semi-inclusive deep
inelastic scattering (SIDIS) and unpolarized Drell-Yan (DY) scattering. It is
shown that recent COMPASS measurements are consistent with the suppression
prescribed by TMD evolution.Comment: 4 pages, 2 figures. Version published in Physical Review Letter
