Gerald H. Thomas

Introductory lectures on fibre bundles and topology for physicists

These lectures may provide useful background material for understanding gauge theories, particularly the nonperturbative effects such as instantons and monopoles. The mathematical language of topology and fibre bundles is introduced.

Evidence for multiple scattering of high energy partons in nuclei

Abstract New experimental information is presented about the effect of a nucleus on partons which have undergone a hard scatter. We have observed clear dijet events from 400 GeV / c p-nucleus interactions and compared them to dijets from pp interactions. Our results show that the angular width of the individual jets is only slightly affected by the presence of the nucleus, but the acoplanarity of the jet pairs is sharply increased.

Evidence that hadronic interiors have a denser matter than charge distribution

Abstract An analysis of high-energy elastic and inelastic diffraction scattering provides strong evidence that the charge and matter densities of hadrons are different. When hadrons are treated as composite objects, then a correct Glauber analysis leads to an optical model with important corrections due to the hadronic wave function: One expects inelastic diffraction due to the fluctuations in the matter density of hadrons. Conversely, the experimental existence of dissociation processes gives phenomenological information about the hadronic wave function. We find the distribution of matter in nucleons to be denser than the observed charge distribution. This result has a natural interpretation from a constituent description of hadrons made from spin 1 2 quarks and colored vector gluons, which is a generalization of the Chou-Yang picture of diffraction scattering.

Evidence for critical point effects in high energy particle multiplicities

Abstract Starting from the gas-liquid analog, a theory for charged particle multiplicities is proposed which allows for both short and long range interactions. Based on the assumptions that at infinite energy, 1) the elementary particle fluid is at a critical point, 2) the basic exchange for the inelastic two prong cross section is dominated by α(0) = 1 2 , and 3) the total inelastic cross section is constant up to factors of 1ns, a no-parameter phenomenological theory is obtained and compared to recent very high energy data. Strong support is found for an approach to the predicted limit.

Equivalence between the Mueller Regge model and the multiperipheral model

Abstract It is proven that a large class of pionization Mueller Regge models are equivalent to the multiperipheral model. An orthogonal similarity transformation is found which allows one to transform in either direction between equivalent multiperipheral and Mueller models. Models with charge are discussed and the problem of constructing charge conserving Mueller models is solved.

Remarks on average pion multiplicities at high energies

Abstract The ISR data on pp → γ imply a Π° transverse momentum spectrum which is consistent with the average of the Π + and Π − spectra, at the same energy, both in shape and in normalization. We are, therefore, able to compare the average numbers of produced pions per inelastic pp collision at the ISR with data at lower energies, and with cosmic ray results.

Longitudinal energy flow in hard proton-nucleus collisions at 400 GeV/c

Using the E609 calorimeter system, we have measured longitudinal energy flow in hard pA collisions which yield dijet final states. The mean laboratory energy flow into the nuclear target (backward) region, nlab < 2.83, minus the value for pp collisions is found to vary as A0.33 ± 0.12, and reaches a value of 50±8 GeV for Pb. The observed probability distribution of energy flow indicates that the energy transfer to a heavy nucleus seldom fluctuates to small values. We also find that the A dependence of the dijet production cross section depends sensitively upon the energy flow to the target region.

Jet production from nuclei at 400 GeV/c

Abstract Results are presented from a calorimeter study on the production of jets in large- E T proton-nucleus collisions at 400 GeV/c. Jet-like large- p T events from eight nuclear targets are seen with a special jet trigger. As previously observed, the cross section for such events increases slightly faster than the atomic number, much like in the production of large- p T single hadrons. Data on energy flows and multiplicities suggest that a heavy nucleus does not significantly widen the angular distribution of the beam remmants. In the central region the particle flow in hard nuclear collisions is similar to that in soft nuclear collisions.

BARYON EXCHANGE AND SHAPES OF INCLUSIVE SPECTRA.

Abstract Contributions of baryon exchanges to inclusive single-pion production processes are investigated. We show that shapes of distributions in p T 2 are reproduced remarkably well by t dependence of simple baryon exchange, but absence of structure at WSNZ positions is noted. Simple Regge models cannot reproduce x (or missing mass) dependence of spectra; to achieve agreement with dat, we introduce and discuss additional modulating functions of x . Spin and absolute normalization are treated.

Towards an understanding of the shapes of inclusive spectra

Abstract Shapes of inclusive distributions as a function of longitudinal momentum are investigated using Regge phenomenology. A dual six-point function is used as a guide to guess the general structure of the single Regge limit. It is found that the shapes are governed by (i) the kinematic relationships between the Mandelstam variables t and M2 and the usual c.m. momentum variables x and P⊥2; (ii) the dynamics due to the intercept of the leading trajectory exchange in the t- (or u -) channel; and (iii) the presence of an exponential damping factor in x which exists in the dual model, and is required to describe the experimental data.