We discuss the possible applications supersymmetric theories might nd in the eld of elementary particle physics. The supersymmetric generalization of the SU(3) SU(2) U(1) standard model is discussed in detail. Special attention has been devoted to the question of gauge coupling constant uni cation in the framework of supersymmetric grand uni ed models. * Lecture given at the conference "Gauge T...

The differences are discussed between various next-to-leading order prescriptions for the QCD evolution of parton densities and structure functions. Their quantitative impact is understood to an accuracy of 0.02%. The uncertainties due to the freedom to choose the renormalization and factorization scales are studied. The quantitative consequences of the different uncertainties on the extraction...

After operations at the LHC and e+e− Linear Colliders it may be found that a Standard-Model-like scenario is realized. In this scenario no new particle will be discovered, except a single Higgs boson having partial widths or coupling constants squared with fundamental particles close, within anticipated experimental uncertainty, to those of the SM. Experiments at a Photon Collider can resolve w...

The nucleon as a relativistic quark-diquark bound state with an exchange potential *). Abstract Treating the quark and diquark as elementary particles, the Bethe-Salpeter equation for the nucleon is solved numerically. The dependence of the mass on the diquark mass and on the coupling constants is investigated. The resulting relativistic quark-diquark-nucleon vertex is presented and discussed.

A search for evidence that fundamental particles are made of smaller subconstituents is performed. The existence of excited states of fundamental particles would be an unambiguous indication of their composite nature. Experimental signatures compatible with the production of excited states of charged leptons in electron-positron collisions are studied. The data analysed were collected by the OP...

A renormalization group flow equation with a scale-dependent transformation of field variables gives a unified description of fundamental and composite degrees of freedom. In the context of the effective average action, we study the renormalization flow of scalar bound states which are formed out of fundamental fermions. We use the gauged Nambu–Jona-Lasinio model at weak gauge coupling as an ex...

We study two type effects of gravitational field on mechanical gyroscopes (i.e. rotating extended bodies). The first depends on special relativity and equivalence principle. The second is related to the coupling (i.e. a new force) between the spins of mechanical gyroscopes, which would violate the equivalent principle. In order to give a theoretical prediction to the second we suggest a spin-sp...

This article is about the interplay between the Standard Model of elementary particle physics and neutron β-decay. Since the Fermi decay constant is known from muon decay, the Standard Model describes neutron β-decay with only two additional parameters. One parameter is the first entry |Vud| of the CKMmatrix. The other one is λ, the ratio of the vector coupling constant and the axial vector con...

We derive the dimensional non-perturbative part of the QCD e ective action for scalar and pseudoscalar meson elds by means of chiral and conformal bosonization. The related structural coupling constants L5 and L8 of the chiral lagrangian are estimated using general relations which are valid in a variety of chiral bosonization models without explicit reference to model parameters. The asymptotic...

First we argue in an informal, qualitative way that it is natural to enlarge space-time to five dimensions to be able to solve the problem of elementary particle masses. Several criteria are developed for the success of this program. Extending the Poincaré group to the group C of all angle-preserving transformations of space-time is one such scheme which satisfies these criteria. Then we show t...