Fig. 2.

Proton–antiproton invariant mass spectrum for candidates originating from a primary vertex (upper panel in each plot), and distribution of differences between data and the background distribution resulting from the fit (lower panel in each plot), in data at a $\sqrt{s}=7\mathrm{TeV}$ and b $\sqrt{s}=8\mathrm{TeV}$ centre-of-mass energies. Distributions on the upper panels are zero-suppressed