abstract

An elementary survey is given of the application of the parton model to large \(p_{\rm T}\) processes. Topics dealt with are: multiple scattering processes, logarithmic scale breaking, the Drell–Yan process, hard scattering mechanisms, parton \(k_{\rm T}\)’s, critical phenomenological questions, downstream calorimetric triggers. The emphasis throughout is on basic ideas and techniques.

abstract

Among the important questions one would like to answer are the following: Why are fractionally charged quarks not observed? Why does the color group SU(3) play such a special role? Indeed, in the standard model, it is, together with the electric charge, the only exact symmetry. Why have leptons integer and quarks fractional charge?

abstract

Two-dimensional QCD is studied as a model for the possible effects of confinement on the predictions of the naive parton model which is based on the free propagation of quark–partons. We find that in processes involving large momentum transfers the naive parton model scaling laws are generally true even though quarks cannot be treated as propagating freely. The universality of quark fragmentation does not extend, however, to hadron–hadron scattering at small momentum transfers. Confinement strongly influences the probability of finding a “wee” quark in a hadron and this leads to a number of interesting consequences.

abstract

Multiparticle production from an experiment designed to search for charmed particles is described and analyzed. A nuclear emulsion stack was bombarded with the Fermilab 150 GeV \(\mu ^+\) beam and a system of counters, proportional chambers and drift chambers, and a magnetic spectrometer were used to detect and momentum analyze the scattered muons. Multiplicity distributions are given and compared with results of proton- and \(\pi ^-\)-emulsion interactions at equivalent energies. A comparison of the pseudo-rapidity distributions is also made. Although there is an over-all similarity between muon and hadron induced multiparticle production on nuclei there are also some clearly marked differences: e.g., muons are, on the average, less efficient than hadrons in producing particles on nuclei. Knowing the angles and energies of the scattered muons we are able to select the processes in which particle multiplication must occur through intra-nuclear cascading. Our data indicate that cascading does exist as one of the effective mechanisms of particle multiplication in \(\mu \)-nucleus collisions. Further experiments investigating the mechanism of this cascading are of considerable interest.

abstract

A simple model for multi-particle production is presented with exact conservation of isospin, assuming that the pions in the final state come from the decay of isospin-one clusters, which consist either of single pions or \(\varrho \)-mesons. The model is shown to reproduce the experimental charged-neutral correlation.