PHENOMENOLOGY OF FUNDAMENTAL INTERACTIONS

We study various aspects of the phenomenology of the standard model and some of its possible extensions, with special regard to the physics of relevance for the present and future high-energy facilities, as B-factories, Tevatron, LHC, neutrino oscillation experiments and e+e- linear colliders.

Special emphasis has been devoted to the following topics:

--Flavour physics and CP violation within and beyond the
standard model:
CKM matrix elements and analysis of the unitarity
triangle;
Rare decays of the b-quark;
Non-leptonic B-decays;
--Neutrino masses in GUT models;
--Higgs and supersymmetry;
--Quark masses and weak matrix elements with lattice QCD;
--Heavy quark production and decays: NLO QCD radiative
corrections, with analysis of exclusive decay modes and
production cross sections;
--All order resummation of kinematically enhanced
contributions in the perturbative expansion;
--Polarized and unpolarized structure functions:
determination of parton distributions and precision tests
of QCD;
--Structure functions at small x: high-energy behaviour and
factorization theorems;
--Electroweak amplitudes for very high-energy e+e-
colliders;
--QCD-based MonteCarlo studies for LHC experiments.


The future activity will be centered along the research lines indicated above and represents their natural development.

In the field of flavour physics, the increasing precision of the data requires a further improvement of the theoretical interpretations. We intend pursuing this activity with the following purposes:
- a higher accuracy in the determination of the CKM matrix elements and in the analysis of the unitarity triangle and of CP violation in the Standard Model will be achieved by including in the analysis the new experimental results as
well as by improving the determination of the theoretical input parameters, particularly the hadronic matrix elements computed with lattice QCD simulations;
- The study of quark mixing and of CP symmetry violation will be extended in the framework of new physics models, in particular supersymmetry and "minimal flavour violation" models;
- The analytic calculations of the two-loop SUSY corrections to flavour processes, in particular Delta F=2, will be completed;
- For non-leptonic B decays, phenomenological models will be further developed, also on the basis of the new experimental results expected from the B-factories;
- The new experimental results on neutrino masses and mixing angles will be further analyzed within GUTs and theories with extra dimensions.

In the field of electroweak physics, the research program will include:
- improving the theoretical prediction of the Higgs boson mass in the Standard Model and beyond for a better comparison between theory and experiments. More specifically, we intend to obtain the complete theoretical prediction, at the two-loop level, of the electroweak effective mixing angle. In the electroweak sector, we also intend to continue the study of very high energy interactions, applied in particular to the calculation of production processes at LHC and electron-positron linear colliders.

In the context of strong interactions physics, the studies of partonic structure functions in the small (and intermediate) x region will be further developed, and the phenomenological comparison of the results with the experimental data will be extended,in particular by developing the phenomenology of the joint GLAP-BFKL resummation which has been developed in recent years. The resummation of the perturbative series in the soft-gluon emission region (large-x) will also be pursued, with the purpose of putting previous results on a firmer theoretical footing, thereby allowing their extension to other cases of physical interest.
The present results obtained in the Regge region for the polarized singlet and non-singlet structure functions will be extended to the unpolarized cases.
The study of power corrections, already performed in the case of the nucleon structure functions, will be extended to the data of deep inelastic scattering on nuclei. Finally, quark model calculations of the generalized parton distributions will be performed and the connection between this model and the QCD sum rules will be investigated.
The use of neural networks as unbiased interpolants, already developed for a precision description of structure functions, will be applied to a quantitative determination of parton distributions and the associate errors.

The development of QCD-MonteCarlos for LHC is quickly rising as the start of the experiments is approaching. The plan is improving the matching of fixed-order calculations with parton-shower approaches to fully simulate multi-jet final states which are the main backgrounds for the discovery of Higgs and SUSY particles. In addition, single-top production will be studied which could be also useful for the measurement of Vtb.

As far as the studies of non-perturbative QCD are concerned, we will continue the research activity based on numerical simulations of lattice QCD. The proposed goals include the first lattice calculation of the SU(3) breaking effects in semileptonic kaon and hyperon decays; a higher precision study of B physics, in particular of the semileptonic and radiative decays and of the mixing processes of neutral B mesons; the study of weak decays of K mesons into two pions; the calculation of the neutron electric dipole moment. A significantly increased accuracy in lattice determinations will be achieved by removing in the numerical simulations the "quenched approximation" which is the main source of systematic error in the results obtained on the lattice, estimated to be typically between 10 and 20%.