Angular distribution of leptons from the decay of massive vector bosons

We examine the transverse momentum Q⊥ dependence of the helicity structure functions for massive vector bosons of mass Q in hadron reactions. We demonstrate that large logarithmic terms of the form ln(Q/Q⊥) in the helicity structure functions have the same origin as the logarithmic terms in the angular-integrated cross section and that they can be resummed to all orders in the strong coupling αs, in the same way as the angular-integrated cross section. As a consequence of current conservation, the resummed part of the helicity structure functions preserves the Lam-Tung relation as a function of Q⊥ to all orders in αs.