Professor Tony Weidberg

Abstract:

We analyze the energy density distribution in harronic final states as a function of their total transverse energy measured in the segmented central calorimeter of the UA2 detector. The energy dependence of collective shape variables is investigated. The data, collected at the CERN {Mathematical expression}p Collider at {Mathematical expression} GeV, exhibit strong variations in all these variables over the transverse energy range between 15 and 210 GeV, corresponding to substantial modifications in the structure of multihadronic final states. The evolution of the energy density distribution and of the collective shape variables shows a clear transition between two extreme dynamical regimes, respectively dominated by pT-limited phase space and by collimated two-jet configurations. A study of the relative populations of two-and three-jet systems reveals two different sources of configurations having three distinct lobes in the pattern of the energy-flow. A first component, steeply falling with energy, receives substantial contributions from soft parton collisions at lower transverse energies. Above 60 GeV a new hard component emerges, characterized by an approximately constant rate with respect to the dominant two-jet structures. © 1987 Springer-Verlag.

Abstract:

Using the UA2 apparatus, the inclusive cross section has been measured for production of high-pT direct photons in p̄p collisions at s=546 GeV and s=630 GeV. The results are in good agreement with QCD predictions. © 1986.

Abstract:

The UA2 experiment, running at the CERN SPS {Mathematical expression} Collider, has performed a study of events containing three hard jets in the final state. The angular distributions of the three jets show evidence for gluon bremsstrahlung, in good agreement with a QCD model to leading order in the strong coupling constant αs. The yield of three-jet events relative to that of two-jet events provides a measure of the strong coupling constant: ;3K3/K2=0.23±0.01±0.04, where K2 and K3 represent the contributions arising from higher order corrections in α3 to the two- and three-jet exclusive cross-sections. A detailed discussion of the systematic and theoretical uncertainties is given. © 1986 Springer-Verlag.