[en] The present status of theoretical calculations for signal and background processes relevant to the Higgs boson search at the LHC is reviewed, with special emphasis on recent developments. The issue of Higgs properties determination at the LHC is addressed

[en] Recent developments in the field of complete electroweak tree-level calculations for six-fermion final states in e⁺e^- collisions are briefly reviewed. Particular attention is given to top-quark and Higgs boson physics, which are items of primary importance at the Next Linear Collider. The relevance of electroweak backgrounds and finite-width effects is discussed, showing the importance of complete calculations for precision studies at the colliders operating in the TeV energy range

[en] The Lhc potential for a measurement of the Higgs boson coupling to the b-quark in the standard model is not very well established yet. We show that requiring a large-transverse-momentum photon in the light Higgs boson production via vector-boson fusion (with subsequent Η → b b decay) could provide a further handle on the Η b b coupling determination and on the measurement of the HWW coupling as well.

[en] The search for new physics in single- and multi-photon final states with large missing energy at LEP and future e⁺e^- colliders requires precise predictions for the Standard Model irreducible background. While at LEP1 the theoretical situation is under control, going to LEP2 (and beyond) some improvements are necessary. To approach the aimed O(1%) theoretical accuracy, the tree-level matrix elements for the processes e⁺e^- → νν-barnγ, with n=1, 2, 3, are exactly computed in the Standard Model, including the possibility of anomalous couplings for single-photon production. Due to the presence of observed photons in the final state, particular attention is paid to the treatment of higher-order QED corrections. Comparisons with existing calculations are shown and commented on. An improved version of the event generator NUNUGPV is presented

[en] We present a study of the Higgs production at the LHC via weak boson fusion, with the Higgs boson decaying into a bb-bar pair. A detailed partonic LO calculation of all the potential backgrounds is performed. We conclude that this channel for Higgs production can be extracted from the backgrounds, and present our estimates of the accuracy in the determination of the Hbb-bar Yukawa coupling

[en] The processes of six-quark production with one bb-bar pair are studied by means of a complete tree-level electroweak calculation. The top-quark signal is examined: the importance of electroweak backgrounds, of the order of 10% above the tt-bar threshold and of about 30% of the purely electroweak signal at threshold, is further stressed by studying the dependence of the cross section at threshold on the Higgs mass in the range between 100 GeV and 185 GeV, and finding variations of the order of 10%. In the study of some event-shape variables, a strong effect of initial-state radiation is found, in particular for the thrust distribution, which is studied for several centre-of-mass energies at the TeV scale. The effectiveness of cuts on the thrust for isolating QCD backgrounds, as pointed out by some authors, is confirmed also in the presence of electroweak backgrounds and initial-state radiation

[en] In this short report we examine the exclusive three-body B→Λ-barpη^' decay using a simple pole model involving a scalar intermediate resonance state. Our aim is to test the recently formulated hypothesis that charmless baryonic B decays could occur mainly in association with η^' or γ

[en] Starting from the phenomenological evidence of four-quark structures in the scalar meson sector around 1 GeV, we investigate the predictions of a model based on diquark-antidiquark bound states, where the diquarks are assumed to contain also heavy quarks. The predictions are compared with the existing data in the charmonium energy range. A comparison of the tetraquark model with alternative interpretations of the exotic reson-cances is presented

[en] It is shown that a Rarita-Schwinger (spin 3/2) particle in an external electromagnetic field besides exhibiting acausal propagation also violates tree unitarity for semi-classical scattering. This suggests a general connection between acausal propagation and the violation of tree unitarity for high-spin (>=1) fields

[en] This work deals with the computation of electron pair correction to small angle Bhabha scattering, in order to contribute to the improvement of luminometry precision at LEP/SLC below 0.1% theoretical accuracy. The exact QED four-fermion matrix element for e⁺e^- → e⁺e^-e⁺e^-, including all diagrams and mass terms, is computed and different Feynman graph topologies are studied to quantify the error of approximate calculations present in the literature. Several numerical results, obtained by a Monte Carlo program with full matrix element, initial-state radiation via collinear structure functions, and realistic event selections, are shown and critically compared with the existing ones. The present calculation, together with recent progress in the sector of O(α²) purely photonic corrections, contributes to achieve a total theoretical error in luminometry at the 0.05% level, close to the current experimental precision and important in view of the final analysis of the electroweak precision data