First-principles calculations of Standard Model parameters at the charm scale and beyond

The search for new physics beyond the Standard Model (SM) is a major endeavour in particle physics, and high precision comparisons between experimental results and theoretical predictions can impose stringent constraints on the proposed extensions. Fundamental processes involving heavy quarks in the flavour sector play a crucial role by giving access to many of the underlying parameters of the SM, a successful theory with impressive levels of precision. In this context, Lattice QCD provides a first-principles numerical approach for studying non-perturbative low-energy aspects of the theory of the strong interaction with high accuracy.

In this thesis we present high precision results in the heavy quark sector from Lattice QCD simulations with non-perturbative O(a)-improved Wilson fermions and Nf =2+1 dynamical flavours.

In the charm quark sector we exploit a mixed-action setup with maximally twisted valence fermions. This approach ensures the absence of O(a) affects proportional to heavy valence masses, thus achieving the automatic improvement regime based on symmetry properties of the regularization. We present precise determinations of the charm quark mass and D(s) meson decay constants, which should improve our current knowledge on the values of some SM parameters and serve as sensitive probes for new physics effects.

In the bottom sector we present the first dynamical quarks calculation of the b-quark mass with a novel approach, obtained by combining Heavy Quark Effective Theory (HQET) and relativistic computations together with step scaling in volume techniques to reach by interpolation the b-quark scale and beyond. The results described in this thesis aim to contribute to the ongoing efforts to understand the fundamental nature of particles and their interactions, by helping to further constrain the world average results of fundamental quantities in the heavy quark sector.