[en] The prospects for the measurement of the strong coupling constant α_MS(M_Z) to a relative uncertainty of 1 % are discussed. Particular emphasis is placed on the implications relating to future High Energy Physics facilities

No abstract available

[en] The authors calculate nonperturbative O (Λ _QCD² / m_c²) corrections to the dilepton invariant mass spectrum and the forward-backward charge asymmetry in B → X_s e⁺e^- decay using a heavy quark expansion approach. The method has recently been used to estimate long-distance effects in B → X_s γ. They generalize this analysis to the case of non-vanishing photon invariant mass, q² ≠ 0, relevant for the rare decay mode B → X_s e⁺e^-. In the phenomena-logically interesting q² region away from the cc-bar resonances, the heavy quark expansion approach should provide a reasonable description of possible non-perturbative corrections. In particular this picture is preferable to the model-dependent approach relying on the tails of Breit-Wigner resonances, which has been employed so far in the literature to account for these effects. They find that the O (Λ _QCD² / m_c²) corrections to the dilepton invariant mass spectrum and to the forward-backward asymmetry in B → X_s e⁺e^-amount to several percent at most for q² / m_b² ≤ 0.3 and q² / m_b² ≤ 0.6 respectively. The O (Λ _QCD² / m_c²) correction to the B → X_s γ decay rate is also computed and found to be +3 % which agrees in magnitude with previous calculations. Finally, they comment on long-distance effects in B → X_s v v-bar, which in this case are extremely suppressed due to the absence of virtual photon contributions

[en] The authors argue that deep-inelastic diffractive scaling provides fundamental insight into the QCD Pomeron. The logarithmic scaling violations seen experimentally are in conflict with the scale-invariance of the BFKL Pomeron and with phenomenological two-gluon models. Instead the Pomeron appears as a single gluon at short-distances, indicating the appearance of a Super-Critical phase of Reggeon Field Theory. That the color compensation takes place at a longer distance is consistent with the Pomeron carrying odd color charge parity

[en] In these lectures the author introduces and explores a range of topics of contemporary interest in hadronic physics: from what drives the formation of a nonzero quark condensate to the effect that mechanism has on light and heavy meson form factors and the properties of the quark-gluon plasma. The trail leads naturally through a discussion of confinement, dynamical chiral symmetry breaking and bound state structure: phenomena that require nonperturbative methods for their explanation. In all of this, the necessary and necessarily momentum-dependent modification of the quark and gluon propagators plays a significant role

[en] A review of strange particle production in heavy ion collisions from AGS to SPS energies is presented. Implications of the newest developments in understanding the collision dynamics and the role of strange particle production in the search for a new phase of matter, in both experimental and theoretical sectors, are discussed

[en] This contribution to the XXVII Symposium on Multiparticle Dynamics held in Frascati, Italy, September, 1997 consists of the following subject matter: (1) introductory generalities; (2) brief mention of some of the contributions to the meeting; (3) more extended discussion of a few specialized topics; (4) discussion of the FELIX initiative for a QCD detector at the LHC

[en] Commensurate scale relations are perturbative QCD predictions which relate observable to observable at fixed relative scales, independent of the choice of intermediate renormalization scheme or other theoretical conventions. A prominent example is the generalized Crewther relation which connects the Bjorken and Gross-Llewellyn Smith deep inelastic scattering sum rules to measurements of the e⁺e^- annihilation cross section. Commensurate scale relations also provide an extension of the standard minimal subtraction scheme which is analytic in the quark masses, has non-ambiguous scale-setting properties, and inherits the physical properties of the effective charge α_V (Q²) defined from the heavy quark potential. The author also discusses a property of perturbation theory, the Abelian correspondence principle, which provides an analytic constraint on non-Abelian gauge theory for N_C → 0

[en] We study the equilibrium thermodynamics of a simple, confining Dyson-Schwinger- equation-model of 2-flavour QCD at finite temperature and chemical potential. The phase boundary between the confined and deconfined phases is defined by the zero of the vacuum-pressure difference. Chiral symmetry restoration and deconfinement are coincident with the transition being of first order, except for μ = 0, where it is second order. Nonperturbative modifications of the dressed-quark propagator persist into the deconfined domain. This entails that the Stefan-Boltzmann limit for the bulk thermodynamic quantities is attained only for large values of temperature and chemical potential. We apply our model to the calculation of the quark condensate and hadronic properties, such as the m_π, ∫_π, π⁰ → γγ and m_p and their dependence on temperature and density. Where a comparison is possible, our results confirm those obtained in numerical simulations of lattice-QCD. We note a tendency for quantities that increase with T to decrease with μ

[en] The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken