At high gluon or string densities, gluon saturation or the strong interaction among strings, either forming color ropes or giving rise to string percolation, induces a strong suppression in the particle multiplicities produced at high energy. This suppression implies important modifications on cosmic ray shower development. In particular, it is shown that it affects the depth of maximum, the elongation rate, and the behavior of the number of muons at energies about ${10}^{17}–{10}^{18}\mathrm{eV}$. The existing cosmic ray data point out in the same direction.

• Received 31 May 2000

DOI:https://doi.org/10.1103/PhysRevLett.86.1674