This is a measurement of the initial state gluon radiation (ISR) in proton-antiproton collisions at √s = 1.96 TeV. This analysis uses Drell-Yan (Z/γ* → ee,μμ) events in the CDF data sample, corresponding to an integrated luminosity of 9.4 fb-1. We find that the mean value of the transverse momentum distribution of the dilepton system is a good observable to measure the effect of the ISR. This observable has a good logarithmic dependence on the mass square of the dileptons, which is parameterized as a linear function of -7.61+2.15log(M2). The measurement of this observable provides a good way to estimate the effect of the ISR at very high mass region, and it can be used to control the size of the ISR effect in other physics processes.
This is dimuon <pT> distribution at each mass bin and combined mass bin after background subtraction. Overall, dimuon <pT> distribution show good agreement.
This is dielectron <pT> distribution at each mass bin and combined mass bin after background subtraction. Overall, dielectron <pT> distribution show good agreement.
The black line is data at reconstruction level and red line is data corrected to generator level. Left plot is muon channel and right plot is electron channel.