the event-by-event fluctuations that are observed in the scattering of the objects.

As was recalled in Sec. \[sec3C\], the linear growth of the variance of the front position is characteristic of reaction-diffusion processes, and is very well seen in the model with saturation, already for moderately small rapidities. The fact that this linear behavior is reproduced by multiple scatterings in the center-of-mass frame (see especially Fig. \[fig:v2000\_2\]) over some finite range of validity may be some evidence in favor of the reaction-diffusion interpretation of high energy scattering. But admittedly, this linear behavior is seen in a very small range for small $1/\alpha^2$. On the other hand, for large $1/\alpha^2$, $y_R>y_F$ and thus the front has not properly relaxed before genuine saturation effects should be taken taken into account, for $y\sim 2y_F$. As a matter of fact, we see that in the range in which the models agree in the case $1/\alpha^2=2\times 10^5$, the asymptotic slope of the variance has not been reached yet. So except for a model in which $y_R\ll y_F$ and $y_F\gg 1$, which are two conditions that are difficult to realize in actual models, it is very difficult to make convincing statements on the ability of bare 