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The system represents an ideal framework for a phenomenological study of the CKM matrix, the validation of its unitarity and independent tests of the CP violation description in the Standard Model (SM). In particular rare decays are among the cleanest probes of the flavour sector of the SM available to present experiments and can reveal the existence of new physics (NP).

A discrete symmetry easily explains all neutrino data. However it is not obvious the embedding of in GUT where all fermions live in the same representation. We show that embedding in it is possible to make distinction between neutrinos and the rest of matter fermions.

The potential of the ATLAS experiment to discover and study the signals expected from the production of Supersymmetric particles with the first few fb of data delivered by the LHC is illustrated.

Almost all the extensions of the Standard Model predict the existence of new charged particles; these particles should be very heavy since they have excaped detection so far. In general, such heavy particles decay as soon as they are produced, but under certain circumstances they can be long-lived or even stable. There are two classes of models which predicts the existence of long-lived particles []: models with a weakly broken symmetry, where the particle would be stable if the symmetry were exact; and models with an exact symmetry which forbids the decay of heavy exotics into ordinary particles, where the decay of the charged particle into a neutral particle is suppressed either by small couplings or by phase space. Examples of the second kind are supersymmetric models with exact -parity, where the lightest supersymmetric particle is the gravitino. In this talk we will focus on GMSB (Gauge Mediated Supersymmetry Breaking) which belongs to this kind of models. In GMSB supersymmetry is broken in a so called hidden sector at a scale and transmitted to SM particles via a messenger sector. The transmission of the supersymmetry breaking is mediated by gauge fields, in particular by singlet representations of (5).

Composite Higgs models [] represent an attractive variation of the Technicolor paradigm []. In these theories the Standard Model (SM) Higgs doublet is the bound state of a strongly interacting sector with flavor symmetry . It forms at a scale , the analog of the QCD pion decay constant, as the Goldstone boson associated with the dynamical breaking of the global symmetry . The couplings of the SM matter and gauge fields to the strong sector break explicitly, and induce a one-loop Higgs potential that triggers the electroweak symmetry breaking (EWSB) at the scale − . In the limit of a large separation = ≪ 1, all the massive bound states of the strong sector decouple, and one is left with the low-energy spectrum of the Standard Model. This means that all corrections to the electroweak precision observables constrained by LEP and SLD experiments will be suppressed by powers of .

It is widely believed now that new physics beyond the Standard Model (SM) will appear at the electroweak scale. In almost all models of electroweak symmetry breaking, top either couples strongly to new particles or its properties are modified in some way, and can be therefore considered as a powerful tool for new discoveries findings. The top quark, discovered about 10 years ago [], is currently being studied in detail by the CDF and D0 experiments at the Tevatron. Its production cross section has been measured in a variety of channels; its mass has been determined to better than 2%, and can be used to constrain the mass of the Higgs. Top quark decays have been tested and nonstandard production mechanisms searched for. So far, all of the top quark’s properties are consistent with the SM, but these studies have to deal with a quite low statistics. LHC instead will be a top factory, with a NLO ( ) equal to about 830 pb for a luminosity of 2 × 10 cm s: this implies the production of two events per second. This enormous sample available will allow to increase the precision of the previously mentioned measurements and will also open up new possibilities such as observation of spin correlations, FCNC in top production and decay, and perhaps even CP violation in the top sector. Many different studies are being actively pursued by tha ATLAS and CMS experiments.

An exciting feature of brane-world models with large extra dimensions [] is that the fundamental scale of gravity could be as low as the electroweak scale ( ≃ 1TeV). Since the mass of a black hole must be larger than , otherwise the classical concept of event horizon would be lost, micro black holes of a few TeV’s may therefore be produced at the LHC in this scenario (for some recent reviews, see []).

The impact of rare decays and Lepton-Flavor Violating processes in shedding light on physics beyond the Standard Model is reviewed. Moreover, we show that tests of Lepton Universality in decays can represent an interesting handle to obtain relevant information on New Physics scenarios.

KLOE data taking at DANE (the Frascati collider) has been terminated on March 2006, after collecting more than 2 fm. The results presented in this article are based on the 450 pb of data taken in 2001 and 2002. The KLOE detector consists of a large cylindrical drift chamber (DC), surrounded by a lead scintillating-fiber electromagnetic calorimeter (EMC) with 4880 PMT’s. A superconducting coil around the calorimeter provides a 0.52T field. The drift chamber [] is 4m in diameter and 3.3m long, filled with a 90%He+10%IsoB gas. The momentum resolution is /⊥ 0.4%. The vertex resolution is ∼ 2mm. The calorimeter [] is divided into a barrel and two endcaps. It covers 98% of the solid angle. Cells close in time and space are grouped into calorimeter clusters. The energy and time resolutions are rispectively . The two-level KLOE trigger [] uses calorimeter and chamber informations. Recognition and rejection of cosmic-ray events is also performed at the trigger level. The KLOE Monte Carlo (MC) program, GEANFI [], includes a full description of the KLOE detector. Machine background is extracted for each run and overlaid with the event generator. Radiative contributions are implemented in the kaon decay generators []. An example of Data-Monte Carlo agreement is shown in Fig. 1, for the main charged decays.

At the Frascati phi-factory Dafne and beams collide in the center of mass energy of the the -meson which decays into anti-collinear pairs. In the laboratory this remains approximately true because of the small crossing angle of the beams. Therefore the detection of a ( ) tags the presence of a () of given momentum and direction. The decay products of the pair define two spatially well separated regions called the tag and the signal hemispheres. Identified decays tag a beam and provide an absolute count, using the total number of tags as normalization. This procedure is a unique feature of a -factory and provides the means for measuring absolute branching ratios. Charged kaons are tagged using the two body decays → μ and → . Since the two body decays correspond to about 85% of the charged kaon decays [] and since BR( → ) ≃ 49% [], there are about 1.5 × 10 events/pb. The two body decays are identified as peaks in the momentum spectrum of the secondary tracks in the kaon rest frame and in the pion mass hypothesis *() In order to minimize the impact of the trigger efficiency, the tagging kaon by itself must provide the event trigger (self-trigger).