Prof. Dr. Ulrich Nierste

Flavour physics studies transitions between quarks of different generations, which are suppressed in the Standard Model by small elements of the Cabibbo-Kobayashi-Maskawa matrix. This feature makes flavour observables highly sensitive to virtual effects of hypothetical heavy new particles. Precision measurements of neutral transitions like b to s or s to d probe new-physics mass scales up to several hundreds of TeV. I discuss the methodology of flavour physics beyond the Standard Model (BSM) and popular explanations of persistent deviations between measurements and SM predictions in certain observables ("flavour anomalies"). I show how one of these, employing scalar leptoquarks, improves the unification of Yuakwa couplings in a grand unified theory with gauge group SO(10). Finally I discuss another research line, addressing searches for light, feebly coupled particles in meson decays, namely axion-like particles in the final states of B meson decays.