Precise study of the $Z/\gamma^*$ boson transverse momentum distribution in $p\bar{p}$ collisions using a novel technique
Phys.Rev.Lett. 106 (2011) 122001, 2011.
The collaboration

Abstract (data abstract)
Fermilab-Tevatron. Measurement of the production of Z0/GAMMA* bosons through dilepton production in PBAR P collisions using 7.3 fb-1 of data collected at a centre-of-mass energy of 1.96 TeV. The experiment measures the variable PHI* which probes the same physical effects as the transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. PHI* is defined as tan(phi(acop)/2)*sin(theta*) where acop is the acoplanarity angle, namely, PI-the difference in azimuthal angle of the two lepton candidates, Theta* is defined through cos(theta*)=tanh((etarap(-)-etarap(+))/2), with etarap(-) and etarap(+) the pseudorapidities of the negatively and positively charged leptons.