Fig. 4.

Observed $\mathit{\beta }$ distributions for the data, corrected for detector effects, and for the MC generators (pythia  6, pythia  8, herwig++, and MadGraph  + pythia  6) in the central ($|{\mathit{\eta }}_2|\le 0.8$) and forward ($0.8<|{\mathit{\eta }}_2|\le 2.5$) regions. The error bars show the statistical uncertainties, while the yellow shaded bands correspond to the combined systematic uncertainty