The Quantum Gauge Principle

We consider the evolution of quantum fields on a classical background space-time, formulated in the language of differential geometry. Time evolution along the worldlines of observers is described by parallel transport operators in an infinite-dimensional vector bundle over the space-time manifold. The time evolution equation and the dynamical equations for the matter fields are invariant under an arbitrary local change of frames along the restriction of the bundle to the worldline of an observer, thus implementing a ``quantum gauge principle''. We derive dynamical equations for the connection and a complex scalar quantum field based on a gauge field action. In the limit of vanishing curvature of the vector bundle, we recover the standard equation of motion of a scalar field in a curved background space-time.Comment: 10 pages (Latex); AMS fonts, dina4p.sty and citesort.sty are neede

On the Space-Time Geometry of Quantum Systems

We describe the time evolution of quantum systems in a classical background space-time by means of a covariant derivative in an infinite dimensional vector bundle. The corresponding parallel transport operator along a timelike curve \cC is interpreted as the time evolution operator of an observer moving along \cC. The holonomy group of the connection, which can be interpreted as a group of local symmetry transformations, and the set of observables have to satisfy certain consistency conditions. Two examples related to local \mbox{SO}(3) and \mbox{U}(1)-symmetries, respectively, are discussed in detail. The theory developed in this paper may also be useful to analyze situations where the underlying space-time manifold has closed timelike curves.Comment: 15 pages (LaTeX); figures are included via epsfig; the corresponding postscript files are uuencoded; AMS-fonts are neede

Prospects for a Measurement of αs\alpha_s via Scaling Violations of Fragmentation Functions in Deeply Inelastic Scattering

The prospects for a determination of the strong coupling constant $\alpha_s$ via scaling violations of fragmentation functions in deeply inelastic scattering are studied. The statistical error in the case of an integrated luminosity of $250 pb^{-1}$, and the theoretical errors due to the various parton density parametrizations and to the factorization scale dependence are estimated.Comment: 6 pages (Latex); figures are included via epsfig. The AMSTEX fonts are required. Based on a contribution to the workshop ``Future Physics at HERA'' at DESY, Hamburg, 1995/96; compressed postscript version also available at http://wwwcn.cern.ch/~graudenz/publications.htm

Projet: Jet Cross Sections in Deeply Inelastic Electron Proton Scattering (VERSION 4.1)

PROJET is a parton level Monte Carlo program for the calculation of jet cross sections in deeply inelastic electron proton scattering. In its present version it contains the Born level diagrams for the production of (1+1), (2+1) and (3+1) jets and the next-to-leading order corrections for the production cross sections of (1+1) and (2+1) jets for all polarisations of the exchanged virtual photon. In particular, the full angular correlations between the lepton and jet momenta are implemented. The program permits the application of acceptance cuts on all external momenta. For this purpose, the program creates an event record accessible to the user program with all momenta in the laboratory frame and in the center of momentum frame of the proton and the virtual photon. This option is indispensable for phenomenological studies because of the strong dependence of cross sections on phase space restrictions and the large uncertainty of fragmentation corrections in the proton direction. Since PROJET uses the Monte Carlo integration method for the evaluation of phase space integrals, the weights of the generated events can be used to produce distributions of observables related to jet momenta.Comment: 28 pages (LaTeX), CERN-TH.7420/9

JET PHYSICS IN DEEPLY INELASTIC SCATTERING AT HERA

We give an overview of jet physics in deeply inelastic scattering at HERA. The problem of jet definitions, the scale dependence of jet cross sections and some applications are discussed. (Talk presented at the Workshop on Deeply Inelastic Scattering and QCD, Paris, April 1995. To appear in the proceedings.)Comment: 5 pages (LaTeX); figures are included via epsfig; the corresponding postscript files are uuencoded. This document needs the qcdparis.sty style file, which is appended between the LaTaX document and the uuencoded figure

Charged-meson production and scaling violations of fragmentation functions in deeply inelastic scattering at HERA

We compare recent experimental results for one-particle-inclusive processes in deeply inelastic scattering at HERA with theoretical predictions in next-to-leading-order QCD perturbation theory, and study the factorization scale dependence of cross sections and charged multiplicities. In the future, for the HERA machine running at design luminosity, scaling violations of fragmentation functions permit the measurement of the strong coupling constant. We estimate the size of the statistical error of \alpha_s that can be achieved, and study the theoretical error due to the various parton density parametrizations and due to the factorization scale dependence

THE PHYSICS OF THE STANDARD MODEL HIGGS BOSON AT THE LHC

Some topics related to Standard Model Higgs boson physics at the Large Hadron Collider are reviewed. Emphasis is put on an overview of QCD corrections to Higgs boson decay and production processes. (Invited talk presented at the XXXth Rencontres de Moriond, Les Arcs 1800, March 19-26, 1995; to appear in the proceedings of the conference.)Comment: 6 pages (LaTeX); figures are included via epsfig; the corresponding postscript files are uuencode

Jets and High-Et Phenomena

The working group on jets and high-Et phenomena of the Future physics at HERA Workshop studied subjects ranging from next-to-leading order (NLO) corrections in deeply inelastic scattering (DIS) and photoproduction with the corresponding determinations of physical quantities, to the physics of instanton-induced processes, where a novel non-perturbative manifestation of QCD could be observed. Other centres of interest were the physics of the forward direction, the tuning of event generators and the development of a new generator which includes a consistent treatment of the small- and large-$x$ QCD evolution. The recommendations of the working group concerning detector upgrades and machine luminosity are summarized