Pseudo-Dirac Solar Neutrinos

Three of the viable solutions of the solar neutrino problem are consistent with close to maximal leptonic mixing: $\sin^2\theta_{12}={1\over2}(1-\epsilon_{12})$ with $|\epsilon_{12}|\ll1$. Flavor models can naturally explain close to maximal mixing if approximate horizontal symmetries force a pseudo-Dirac structure on the neutrino mass matrix. An experimental determination of $|\epsilon_{12}|$ and sign($\epsilon_{12}$) can constrain the structure of the lepton mass matrices and consequently provide stringent tests of such flavor models. If both $|\epsilon_{12}|$ and $\Delta m^2_{21}$ are known, it may be possible to estimate the mass scale of the pseudo-Dirac neutrinos. Radiative corrections to close to maximal mixing are negligible. Subtleties related to the kinetic terms in Froggatt-Nielsen models are clarified.Comment: 24 pages; v3: significant improvements and modifications, particularly in the three generation analysi

CP violation in meson decays

This is a written version of a series of lectures aimed at graduate students in the field of (theoretical and experimental) high energy physics. The main topics covered are: (i) The flavor sector of the Standard Model and the Kobayashi-Maskawa mechanism of CP violation; (ii) Formalism and theoretical interpretation of CP violation in meson decays; (iii) K decays; (iv) D decays; (v) B decays: b -> c c-bar s, b -> s s-bar s, b -> u u-bar d and b -> c u-bar s, u c-bar s; (vi) CP violation as a probe of new physics and, in particular, of supersymmetry.Comment: 67 pages, 7 figures; Lectures given at the `Third CERN-CLAF School of High Energy Physics', Malargue (Argentina) 3/2005, and at the Les Houches Summer School (Session LXXXIV) on `Particle Physics Beyond the Standard Model,' Les Houches (France) 8/200

The Higgs program and open questions in particle physics and cosmology

The Higgs program is relevant to many of the open fundamental questions in particle physics and in cosmology. Thus, when discussing future collider experiments, one way of comparing them is by assessing their potential contributions to progress on these questions. We discuss in detail the capabilities of the various proposed experiments in searching for singlet scalars, which are relevant to several of the open questions, and in measuring Higgs decays to fermion pairs, which are relevant to the flavor puzzles. On other interesting questions, we list the most relevant observables within the Higgs program.Comment: 17 pages, 1 figur

Relating direct CP violation in D decays and the forward-backward asymmetry in ttˉt\bar t production

The CDF and LHCb experiments have recently provided two intriguing hints for new physics: a large forward-backward asymmetry in $t\bar t$ production, and a direct CP asymmetry in D decays of order a percent. In both cases, flavor non-universal interactions are required in the up sector, raising the possibility that the two effects come from one and the same new physics source. We show that a minimal model, with an extra scalar doublet, previously suggested to explain the top data, gives -- without any modifications or additions -- a contribution to CP violation in charm decays that is of the right size.Comment: 4 pages. v3: A calculation of the contribution to epsilon^prime is presented; Conclusions unchange