Multiplicity Growth and Leading Particle Energy Loss

The relation between the multiplicity growth and the energy loss spectrum of an incident particle, as implied by Poisson emission with a classical spectrum, appears to be obeyed experimentally in PP collisions. (Submitted to Phys. Rev. Letters) * Work supported by the U. S. Atomic Energy Commission. The Brookhaven experiments’ on the behavior of the final proton in highly inelastic PP collisions at GeV revealed a spectrum of puzzling simplicity: to a first approximation the emerging proton can have any value of longitudinal momentum with equal probability, as long as that momentum is large, That is, the cross section do/dPL in P +P 4 P + (anything) for fast final protons is, aside from the narrow elastic and quasi-elastic structures at the maximum momentum, approximately independent of PL. (It is worth noting that this statement, or that of any power law behavior do/dPL I Pa, holds in all frames reached by Lorentz transformations leaving the proton moving relativistically in the same direction.) Subsequent experiments2 have confirmed these results. In Fig. 1 we show the CERN results at 19 GeV/c. Since that time, some preliminary understanding of the situation at very high energy, beyond the region where resonances and quasi-two body reactions dominate the scattering channels, has been achieved. The average multiplicity3 appears to increase logarithmically at very large energy so that, ignoring a constant term, N=CQns . (1) The constant C is approximately one if we multiply the experimental charged 01 multiplicity of (0.7 k 0.1) by 3/2 to attempt to account for undetected r s. The multiparticle production spectra may be dominated by “soft pions, I1 4 whose probability distribution peaks for very low energy. These features are reminiscent of a simple “bremsstrahlung picture, ” an idea entertained, with just these points in mind, at least as far back as 1942,’ and elaborated recently in the context of llscalingfl by Feynman. In “bremsstrahlung’! the abrupt acceleration of