Guido Martinelli - The golden ratio: from quenched spectroscopy to unquenched radiative decays

30th March 2023
Phenomenology with lattice QCD was born in 1981 with the Hamber-Parisi paper ”Numerical Estimates of Hadronic Masses in Pure SU(3) Gauge Theories”. Since then numerical simulations of Lattice QCD with Fermions (LQCD) allowed an unpreceded progress in understanding the non-perturbative dynamics of strong interactions. Precise calculations of the hadron spectrum and accurate predictions of hadronic matrix elements are now a reality and more and more quantities relevant to the phenomenology of the Standard Model (SM) and for searches of signals of new physics beyond the SM (BSM) will soon become available. This progress has been possible thanks to the development of very sophisticated theoretical tools coupled to an extraordinary increase of the computer power and memory. In this talk a brief description of the methods of LQCD and of the main achievements obtained in recent years will be presented. Besides the hadron spectrum, lattice calculations are used to study the dynamics of QCD at large temperature or chemical potential, the anomalous magnetic moment of the muon, g − 2, the nucleon structure functions, the meson scattering amplitudes at low and intermediate energies and, last but not least, the weak matrix elements relevant in flavour physics and CP violation. In this presentation only some examples particularly illustrative of the present sophistication and accuracy of lattice QCD calculations will be discussed in some detail.