Polarized parton distributions in perturbative QCD

We review the main results of next-to-leading order QCD analyses of polarized deep-inelastic scattering data, with special attention to the assessment of theoretical uncertainties.Comment: 4 pages Latex, 1 ps figure. Talk given at NUCLEON '99, Frascati(Italy), June 7-9 199

Status of the Standard Model at the LHC Start

I present a concise review of where we stand in particle physics today. First, I will discuss QCD, then the electroweak sector and finally the motivations and the avenues for new physics beyond the Standard Model.Comment: Plenary Talk at the 5th Italian Workshop on p-p Physics at the LHC. 13 pages, no figure

Concluding talk: fundamental lessons and challenges from neutrinos

We present a concise review of the experimental developments on neutrino mixing and their theoretical implications as presented and discussed at this Conference. The recent data disfavour many models but the surviving ones still span a wide range going from Anarchy (no structure, no symmetry in the neutrino sector) to a maximum of symmetry, as for the models based on discrete non-abelian flavour groups which can be improved following the indications from the recent data.Comment: 20 pages, no figures. Talk given at the Pontecorvo 100 Symposium in honour of Bruno Pontecorvo for the centennial of the birth, Pisa, 18-20 September 2013. arXiv admin note: text overlap with arXiv:1304.5047, arXiv:1111.6421, arXiv:1210.346

An Overview of Neutrino Mixing

We present a concise review of the recent important experimental developments on neutrino mixing (hints for sterile neutrinos, large $\theta_{13}$, possible non maximal $\theta_{23}$, approaching sensitivity on $\delta_{CP}$) and their implications on models of neutrino mixing. The new data disfavour many models but the surviving ones still span a wide range going from Anarchy (no structure, no symmetry in the lepton sector) to a maximum of symmetry, as for the models based on discrete non-abelian flavour groups.Comment: 6 pages, no figures. Talk given at the Fourth Workshop on Theory, Phenomenology and Experiments in Flavour Physics, June 2012, Capri, Ital

The Standard Electroweak Theory and Beyond

1. Introduction, 2. Gauge Theories, 3. The Standard Model of Electroweak Interactions, 4. The Higgs Mechanism, 5. The CKM Matrix, 6. Renormalisation and Higher Order Corrections, 7. Why we do Believe in the Standard Model: Precision Tests, 7.1.Precision Electroweak Data and the Standard Model, 7.2.A More General Analysis of Electroweak Data, 8. Why we do not Believe in the Standard Model, 8.1.Conceptual Problems, 8.2.Hints from Experiment, -8.2.1 Unification of Couplings, -8.2.2 Dark Matter, -8.2.3 Neutrino Masses, -8.2.4 Baryogenesis, 9. Status of the Search for the Higgs and for New Physics, 10.ConclusionComment: 59 pages, 9 figures, Lectures given at the Nathiagali Summer School, Pakistan and the PSI Zuoz Summer School, July - August 200

The crucial problem: the electroweak symmetry breaking

1. Why we do Believe in the Standard Model 2. Why we do not Believe in the Standard Model 2.1 Conceptual Problems 2.2 Hints from Experiment 2.2.1 Unification of Couplings 2.2.2 Dark Matter 2.2.3 Neutrino Masses 2.2.4 Baryogenesis 3. Status of the Search for the Higgs and for New Physics 4. ConclusionComment: 16 pages, Talk, XI Rencontres de Blois, Frontiers of Matter, 27 June-3 July 199

Neutrino Tribimaximal Mixing from A_4 Alone

Neutrino tribimaximal mixing is obtained from the breaking of A_4 to Z_3 in the charged-lepton sector and to Z_2 in the neutrino sector. To enforce this conflicting pattern, extra particles and symmetries are usually invoked, often accompanied by nonrenormalizable interactions and even extra dimensions. It is shown here in a specific renormalizable model how A_4 alone will accomplish this, with only the help of lepton number.Comment: 8 pages, no figure, reference correcte

One light composite Higgs boson facing electroweak precision tests

We study analytically and numerically the bounds imposed by the electroweak precision tests on a minimal composite Higgs model. The model is based on spontaneous SO(5)/SO(4) breaking, so that an approximate custodial symmetry is preserved. The Higgs arises as a pseudo-Goldstone boson at a scale below the electroweak symmetry breaking scale. We show that one can satisfy the electroweak precision constraints without much fine-tuning. This is the case if the left-handed top quark is fully composite, which gives a mass spectrum within the reach of the LHC. However a composite top quark is strongly disfavoured by flavour physics. The alternative is to have a singlet top partner at a scale much lighter than the rest of the composite fermions. In this case the top partner would be light enough to be produced significantly at the LHC.Comment: 15 pages, 4 figures; v2: figures and discussion improved, references added; v3: minor changes, final version to appear in PR