abstract

The screening theorem is discussed, and its consequences for the Higgs system are exhibited. Next the present situation with respect to possibilities for the Higgs system is discussed.

abstract

I review a few issues on first order transitions. The motivation arises from unexpected peculiarities encountered in numerical simulations of rather common classical spin systems, and relative to the finite size behaviour of thermodynamical quantities such as the specific heat or higher order energy cumulants. The \(q\)-states 2-d Potts model is discussed in some details, in order to state the problems met as well as to propose explanations and to remedy to their consequences in numerical simulation analysis. Emphasis is put on the relationship between the finite size behaviour of the partition function and that of the internal energy distributions.

abstract

The evidence for flux tubes from lattice QCD simulations is briefly reviewed. Then I present results of a detailed study of topological properties of QCD vacuum configurations below and above the deconfinement phase transition, both without and with dynamical quarks. The topological properties were probed by two local operators of topological-charge density and the cooling method. Results obtained using both definitions are compared and lessons from cooling experiments are briefly summarized. The flux-tube formation is seen to be reflected in topological-charge distributions.

abstract

After a pedagogical introduction to the calculation of weak matrix elements on the lattice, I review some of the lattice’s most recent predictions concerning the weak decays of \(B\)-mesons. Amongst the topics covered are the determinations of the leptonic decay constant \(f_B\), of the form factors relevant for semi-leptonic \(B \to D(D^*)\ell \bar \nu \) decays and of the hadronic matrix element which describes the rare decay \(B \to K^* \gamma \). Emphasis is placed on the results of the UKQCD Collaboration. Corrections to the heavy-quark limit are discussed extensively.

abstract

The quenched approximation for QCD is, at present and in the foreseeable future, unavoidable in lattice calculations with realistic choices of the lattice spacing, volume and quark masses. In these lectures, I review the analytic study of the effects of quenching based on chiral perturbation theory. Quenched chiral perturbation theory leads to quantitative insight into the difference between quenched and unquenched QCD, and reveals clearly diseases which plague quenched QCD. A short review of the ideas underlying chiral perturbation theory is included.

abstract

The pion multipoles of static Skyrmions with arbitrary baryon number are discussed. It is shown that a monopole moment cannot occur. The forces between separated Skyrmions are dominated by the dipole–dipole interaction, in general, and this gives some understanding of the structure of Skyrmions with baryon number up to four.

abstract

We summarize the experimental results on integrals over the spin-dependent structure function of nucleons \(g_1(x, Q^2)\). We comment on what data tell us about the origin of the spin of the proton, and compare results with a calculation from a chiral bag model.

abstract

A critical survey of recent developments in the description of exclusive reactions is given. An approach to nucleon distribution amplitudes and related properties is discussed, which makes use of QCD sum rules and the renormalization group. The behavior of helicity-conserving nucleon form factors in the spacelike region has been studied in detail, emphasizing the importance of a self-consistent treatment of endpoint contributions via a modified QCD factorization which takes into account Sudakov suppression of soft-gluon radiation. None of the considered observables is inconsistent with the data, although the leading perturbative contribution to the pion and nucleon form factors is small, calling for rather large K-factors and/or sizeable higher-twist contributions.

abstract

Selected results concerning the spectroscopy of \(b\bar b\) quarkonia and the semileptonic and leptonic decays of hadrons containing \(b\)-quarks are reviewed. Problems concerning the inclusion of relativistic corrections and the interpretation of wave functions are pointed out.

abstract

We review the recent developments of studies on \(e^+e^- \to t\bar t\) in the threshold region. It has been shown that the top threshold cross sections will be able to provide many important and interesting physics. Due to the large mass and the large decay width of top quark, there will appear a number of unique features at top threshold. First, theoretical background is summarized. Then we present observables that are typical to the top threshold region, and discuss the physics that can be extracted. Also, we list the results of the recent parameter determination study taking a sample case of \(m_t = 170\) GeV.

abstract

Recent results obtained at LEP on the production and decays of these “new” B states are presented.

abstract

Recent experimental results in deep inelastic \(ep\) scattering from the H1 and ZEUS experiment at HERA are presented. These include the latest measurements on the structure function \(F_2\), a measurement of \(\alpha _S(M^2_Z)\) with jets, charged particle spectra in the Breit frame and studies with events exhibiting large rapidity gaps.

abstract

Results from photoproduction at HERA are presented, including cross section measurements for \(\rho ^0\), \(\phi \), and \(J/\psi \) production. We have found jets which are a signature for hard scattering processes. An analysis of two-jet events allows us to probe the structure of both the photon and the proton. Comparisons are made of di-jet production to predictions from LO QCD, using different structure functions of the proton and photon. We have searched for hard scattering in diffractive events and compared our results to models where the exchanged pomeron is composed of partons.

abstract

Missing energy and momentum experiments in high energy particle physics are reviewed. The techniques, problems and successes of such experiments are discussed using the historical example of the \(\beta \) decay, as well as the discoveries of the \(\tau \) lepton and of the \(W\) boson. Recent missing energy experiments at the \(Z^0\) peak, demonstrate the feasibility of the indirect neutrino detection method in large multi purpose detectors. The importance of missing energy detection capabilities for future experiments is emphasized with several search studies for new exotic phenomena at LEP2, the LHC and at a linear \(e^+e^-\) collider.