## FLAG review on the cover of EPJ-C

October 31, 2014

The figure shows a collection and a world-average of recent lattice determinations of $$B$$ and $$B_s$$ mesons decay constants, which are the hadronic parameters entering the theoretical expressions of leptonic decay rates. These transitions are experimentally measured at B-factories and LHCb.
We review lattice results related to pion, kaon, $$D$$- and $$B$$-meson physics with the aim of making them easily accessible to the particle physics community. More specifically, we report on the determination of the light-quark masses, the form factor $$f_+(0)$$, arising in semileptonic $$K \rightarrow \pi$$ transition at zero momentum transfer, as well as the decay constant ratio $$f_K/f_\pi$$ of decay constants and its consequences for the CKM matrix elements $$V_{us}$$ and $$V_{ud}$$. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of $$SU(2)_L x SU(2)_R$$ and $$SU(3)_L x SU(3)_R$$ Chiral Perturbation Theory and review the determination of the $$B_K$$ parameter of neutral kaon mixing. The inclusion of heavy-quark quantities significantly expands the FLAG scope with respect to the previous review. Therefore, for this review, we focus on $$D$$- and $$B$$-meson decay constants, form factors, and mixing parameters, since these are most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. In addition we review the status of lattice determinations of the strong coupling constant $$\alpha_s$$.