Relative width of Δφ between the track-based missing transverse momentum (Track ETmiss) and two event-based quantities in events with W bosons, as a function of the number of primary vertices for collision data and for simulation. The plot serves to illustrate the pileup dependence of the quantity Δφ(Track ETmiss, ETmiss) (red circles), where the event missing transverse momentum (ETmiss) used here is represented by the missing ET calculated from the calorimeter objects and the muon transverse momentum. The stability of the Track ETmiss quantity is illustrated by the Δφ(Track ETmiss, pTlep) distribution (blue triangles), where the φ coordinate of the isolated lepton from the decay of the W is used because of its very precise reconstruction. The Δφ width is shown relative to the width at Npv = 2.