It is shown that the choice of a Planck distribution for the cluster-decay function in the diffractive excitation model gives good agreement with the inclusive transverse-momentum spectrum of pions in $\mathrm{pp}$ collisions. Since this kind of distribution is associated with the thermodynamic model, the relationship between the two models is examined.

• Received 18 December 1972

DOI:https://doi.org/10.1103/PhysRevD.8.971