Non-perturbative renormalization of tensor currents: strategy and results for Nf=0N_f = 0 and Nf=2N_f = 2 QCD

Tensor currents are the only quark bilinear operators lacking a non-perturbative determination of their renormalisation group (RG) running between hadronic and electroweak scales. We develop the setup to carry out the computation in lattice QCD via standard recursive finite-size scaling techniques, and provide results for the RG running of tensor currents in $N_f = 0$ and $N_f = 2$ QCD in the continuum for various Schr\"odinger Functional schemes. The matching factors between bare and renormalisation group invariant currents are also determined for a range of values of the lattice spacing relevant for large-volume simulations, thus enabling a fully non-perturbative renormalization of physical amplitudes mediated by tensor currents.Comment: 50 pages, 14 Figure

A tmQCD mixed-action approach to flavour physics

We discuss a mixed-action approach in which sea quarks are regularised using non-perturbatively ${\rm O}(a)$ improved Wilson fermions, while a fully-twisted tmQCD action is used for valence quarks. In this setup, automatic ${\rm O}(a)$ improvement is preserved for valence observables, apart from small residual ${\rm O}(a)$ effects from the sea. A strategy for matching sea and valence is set up, and carried out for $N_\mathrm{f}=2+1$ CLS ensembles with open boundary conditions at several simulation points. The scaling of basic light-quark observables such as the pseudoscalar meson decay constant is studied, as well as the isospin splitting of pseudoscalar meson masses.Comment: 11 pages, 5 figures, Proceedings of the 35th International Symposium on Lattice Field Theory (Lattice 2017), 18-24 June 2017, Granada, Spai

Non-perturbative running of quark masses in three-flavour QCD

We present our preliminary results for the computation of the non-perturbative running of renormalized quark masses in $N_f = 3$ QCD, between the electroweak and hadronic scales, using standard finite-size scaling techniques. The computation is carried out to very high precision, using massless $\mathcal{O}(a)$-improved Wilson quarks. Following the strategy adopted by the ALPHA Collaboration for the running coupling, different schemes are used above and below a scale $\mu_0 \sim m_b$, which differ by using either the Schr\"odinger Functional or Gradient Flow renormalized coupling. We discuss our results for the running in both regions, and the procedure to match the two schemes.Comment: 7 pages, 3 figures, 34th annual International Symposium on Lattice Field Theor

Non-perturbative quark mass renormalisation and running in Nf=3N_f=3 QCD

We determine from first principles the quark mass anomalous dimension in Nf=3 QCD between the electroweak and hadronic scales. This allows for a fully non-perturbative connection of the perturbative and non-perturbative regimes of the Standard Model in the hadronic sector. The computation is carried out to high accuracy, employing massless O(a)-improved Wilson quarks and finite-size scaling techniques. We also provide the matching factors required in the renormalisation of light quark masses from lattice computations with O(a)-improved Wilson fermions and a tree-level Symanzik improved gauge action. The total uncertainty due to renormalisation and running in the determination of light quark masses in the SM is thus reduced to about 1%.Comment: 41 pages, 10 tables, 7 figures, published version (minimal text improvements

Strong coupling from non-equilibrium Monte Carlo simulations

We compute the running coupling of non-Abelian gauge theories in the Schr\"odinger-functional scheme, by means of non-equilibrium Monte Carlo simulations on the lattice.Comment: v1: 29 pages, 7 figures; v2: 1+46 pages, 9 figures: added a detailed discussion of the algorithm, computational efficiency analysis, comparison with perturbation theory at loops, new references, corrected typos (version published in the journal

Determination of Fundamental Parameters in the Hadronic Sector of the Standard Model

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 15-09-201