multiple scatterings to mimic a reaction-diffusion process.

So far, we have considered boost-invariant saturation only. Boost invariance is a basic requirement for the model to be consistent with field theory. We wish however to compare to a non boost-invariant scheme.

Other (non boost-invariant) saturation scheme
---------------------------------------------

We adopt the alternative scheme of saturation which consists in vetoing further particle splittings to a site as soon as the number of particles on this very site has reached the value $1/\alpha^2$ (see Sec. \[sec3B\]). The small-$\alpha$ asymptotics of the statistics of the front position should be insensitive to the exact way how saturation occurs. However, subleading effects at finite $\alpha$ have no reason to be identical.

We see indeed in Fig. \[fig:veto2000\_1\] that the asymptotic velocity is higher for this scheme than for boost-invariant saturation. Moreover, multiple-scattering unitarization leads to a velocity that, at low $y$, is closer to the one obtained from the veto procedure.

However, if one observes the variance of the position of the front (Fig. \[fig:veto2000\_2\]), one sees that the large-$y$ slope is quite different between the veto scheme and the boost-invariant scheme. Around $y\sim 50$, it is clear that the unitarization scheme is much closer to boost-invariant 