Fig. 2.

Calculated invariant energy spectrum $x_{E}d{n}_{pp}^{{\pi }^0}/d{x}_{\text{F}}$, with $x_{\text{E}}=2E/\sqrt{s}$, of neutral pions (red line) in the c.m. frame for pp-collisions at $\sqrt{s}=7$ TeV, compared to the data (black errorbars) of the LHCf experiment [13].