First Lattice Calculation of the QED Corrections to Leptonic Decay Rates.

The leading-order electromagnetic and strong isospin-breaking corrections to the ratio of K_{µ2} and π_{µ2} decay rates are evaluated for the first time on the lattice, following a method recently proposed. The lattice results are obtained using the gauge ensembles produced by the European Twisted Mass Collaboration with N_{f}=2+1+1 dynamical quarks. Systematic effects are evaluated and the impact of the quenched QED approximation is estimated. Our result for the correction to the tree-level K_{µ2}/π_{µ2} decay ratio is -1.22(16)%, to be compared to the estimate of -1.12(21)% based on chiral perturbation theory and adopted by the Particle Data Group.

Review of lattice results concerning low-energy particle physics: Flavour Lattice Averaging Group (FLAG).

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 [Formula: see text], arising in the semileptonic [Formula: see text] transition at zero momentum transfer, as well as the decay constant ratio [Formula: see text] and its consequences for the CKM matrix elements [Formula: see text] and [Formula: see text]. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of [Formula: see text] and [Formula: see text] Chiral Perturbation Theory. We review the determination of the [Formula: see text] parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. The latter quantities are an addition compared to the previous review. For the heavy-quark sector, we provide results for [Formula: see text] and [Formula: see text] (also new compared to the previous review), as well as those for D- and B-meson-decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. Finally, we review the status of lattice determinations of the strong coupling constant [Formula: see text].

Review of lattice results concerning low-energy particle physics.

We review lattice results related to pion, kaon, [Formula: see text]- and [Formula: see text]-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 [Formula: see text], arising in semileptonic [Formula: see text] transition at zero momentum transfer, as well as the decay-constant ratio [Formula: see text] of decay constants and its consequences for the CKM matrix elements [Formula: see text] and [Formula: see text]. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of [Formula: see text] and [Formula: see text] Chiral Perturbation Theory and review the determination of the [Formula: see text] parameter of neutral kaon mixing. The inclusion of heavy-quark quantities significantly expands the FLAG scope with respect to the previous review. Therefore, we focus here on [Formula: see text]- and [Formula: see text]-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 [Formula: see text].

Constraints on new physics from the quark mixing unitarity triangle.

The status of the unitary triangle beyond the standard model including the most recent results on Deltam[s] on dilepton asymmetries and on width differences is presented. Even allowing for general new physics loop contributions the unitarity triangle must be very close to the standard model result. With the new measurements from the Fermilab Tevatron, we obtain for the first time a significant constraint on new physics in the Bs sector. We present the allowed ranges of new physics contributions to DeltaF=2 processes and of the time-dependent CP asymmetry in Bs-->J/psivarphi decays.