High precision flavour physics

Flavour Physics is a very powerful tool to test the Standard Model and quantify the effects of New Physics by exploring possible departures from the model. It is necessary, however, to increase the level of precision of the experimental measurements and of the theoretical predictions in order to be sensitive to possible deviations. In this thesis we address this issue by providing theoretical improvements for both non-perturbative and perturbative calculations of some relevant flavour observables. On the one hand, we present a new strategy to renormalize lattice operators in QCD+QED in the RI-MOM scheme, fully including the non perturbative dynamics of QCD, and QED at O(αem). We show how to keep systematically into account all contributions not separable between the two interactions, thus overcoming the factorization approximation in which the mixed effects are neglected. A numerical analysis in the electro-quenched approximation is carried out for quark bilinear operators and for the case of the matrix elements relevant for Kl2 and πl2 processes and for semileptonic decays like Kl3. A detailed discussion of the calculation of the leading isospin breaking corrections to the leptonic decay rates Γ(Kμ2) and Γ(πμ2) is presented. On the other hand, we compute for the first time the anomalous dimension matrices of quark bilinear and weak four-fermions semileptonic operators at O(αs αem), thus improving the evolution and matching of the matrix elements related to such operators in Effective Field Theories

First examples of pyran based colorants as sensitizing agents of p-Type Dye-Sensitized solar cells

Three different pyran based dyes were synthesized and tested for the first time as photosensitizers of NiO based p-type dye-sensitized solar cells (p-DSSC). The molecules feature a similar molecular structure and are based on a pyran core that is functionalized with electron acceptor groups of different strength and is symmetrically coupled to phenothiazine donor branches. Optical properties of the dyes are deeply influenced by the nature of the electron-acceptor group, so that the overall absorption of the three dyes covers the most of the visible spectrum. The properties of devices based on the NiO electrodes sensitized with the investigated dyes were evaluated under simulated solar radiation: the larger short circuit current density exceeded 1mA/cm2 and power conversion efficiency as high as 0.04% could be recorded. The performances of the fabricated p-DSSC have been compared to a reference cell sensitized with P1, a high level benchmark, which afforded a photoelectrochemical activity similar to the best example of our pyran sensitized devices (1.19 mA/cm2 and 0.049%)

Critical behaviour of the O(3) nonlinear sigma model with topological term at theta=pi from numerical simulations

We investigate the critical behaviour at theta=pi of the two-dimensional O(3) nonlinear sigma model with topological term on the lattice. Our method is based on numerical simulations at imaginary values of theta, and on scaling transformations that allow a controlled analytic continuation to real values of theta. Our results are compatible with a second order phase transition, with the critical exponent of the SU(2)_1 Wess-Zumino-Novikov-Witten model, for sufficiently small values of the coupling.Comment: Revised version. 24 pages, 7 figure

Anisotropic Effects of Oxygen Vacancies on Electrochromic Properties and Conductivity of γ\gamma-Monoclinic WO3_3

Tungsten trioxide (WO$_3$) is a paradigmatic electrochromic material, whose peculiar optical properties in the presence of oxygen vacancies or intercalated alkali atoms have been observed and investigated for a long time. In this paper we propose a rationalization of experiments based on first-principles calculations of optical and electrical properties of oxygen deficient (reduced) WO$_3$. Our approach is based on a parameter-free dielectric-dependent hybrid density functional methodology, used in combination with the charge transition levels formalism, for studying excitation mechanisms in the presence of defects. Our results indicate that oxygen vacancies lead to a different physics in $\gamma$-monoclinic WO$_3$, depending on the orientation of the W-O-W chain where the vacancy is created, thus evidencing strong anisotropic effects rooted in the peculiar structural properties of the original nondefective monoclinic cell. Different types of oxygen vacancies can hence be classified on the basis of the calculated ground state properties, electronic structure, and excitation/emission energies, giving a satisfactory explanation to a range of experimental observations made on oxygen deficient WO$_3$.Comment: Accepted for publication in J. Phys. Chem.

Autoimmune diseases and their manifestations on oral cavity: diagnosis and clinical management

Oral signs are frequently the first manifestation of autoimmune diseases. For this reason, dentists play an important role in the detection of emerging autoimmune pathologies. Indeed, an early diagnosis can play a decisive role in improving the quality of treatment strategies as well as quality of life. This can be obtained thanks to specific knowledge of oral manifestations of autoimmune diseases. This review is aimed at describing oral presentations, diagnosis, and treatment strategies for systemic lupus erythematosus, Sjögren syndrome, pemphigus vulgaris, mucous membrane pemphigoid, and Behcet disease

Defect calculations in semiconductors through a dielectric-dependent hybrid DFT functional: the case of oxygen vacancies in metal oxides

We investigate the behavior of oxygen vacancies in three different metal-oxide semiconductors (rutile and anatase TiO2, monoclinic WO3, and tetragonal ZrO2) using a recently proposed hybrid density-functional method in which the fraction of exact exchange is material-dependent but obtained ab initio in a self-consistent scheme. In particular, we calculate charge-transition levels relative to the oxygen-vacancy defect and compare computed optical and thermal excitation/emission energies with the available experimental results, shedding light on the underlying excitation mechanisms and related materials properties. We find that this novel approach is able to reproduce not only ground-state properties and band structures of perfect bulk oxide materials, but also provides results consistent with the optical and electrical behavior observed in the corresponding substoichiometric defective systems.Comment: Accepted for publication in J. Chem. Phy

Electronic structure and phase stability of oxide semiconductors: Performance of dielectric-dependent hybrid functional DFT, benchmarked against GWGW band structure calculations and experiments

We investigate band gaps, equilibrium structures, and phase stabilities of several bulk polymorphs of wide-gap oxide semiconductors ZnO, TiO2,ZrO2, and WO3. We are particularly concerned with assessing the performance of hybrid functionals built with the fraction of Hartree-Fock exact exchange obtained from the computed electronic dielectric constant of the material. We provide comparison with more standard density-functional theory and GW methods. We finally analyze the chemical reduction of TiO2 into Ti2O3, involving a change in oxide stoichiometry. We show that the dielectric-dependent hybrid functional is generally good at reproducing both ground-state (lattice constants, phase stability sequences, and reaction energies) and excited-state (photoemission gaps) properties within a single, fully ab initio framework.Comment: Minor changes in the final published versio