Hadronic decays

Hadronic decays and transitions are a key ingredient of hadronic physics. I discuss how hadronic decays can be explored in lattice gauge theory and review studies undertaken. I also discuss the impact of decays on masses and how lattice studies can explore the nature of a hadronic state: namely whether it is a molecular or quark-antiquark state. A brief discussion of lattice exploration of pentaquark states is presented.Comment: 14 pages, plenary talk at Lattice 2005, Dublin, July 25-3

The eta and eta' mesons from lattice QCD

Lattice QCD allows a first-principles study of QCD with the freedom to vary the number and masses of the quarks. I present results on the flavour singlet correlations (this illuminates OZI violating effects) for mesons. Concentrating on the pseudoscalar mesons, the flavour singlet mass splitting ($\eta$, $\eta'$ mass splitting) appears naturally. I also present results on an investigation of decay constants for the $\eta$ and $\eta'$ ($f_{\eta}$) and discuss which quantities may be accessible in future lattice studies. The Witten-Veneziano approach can also be explored by determining the quenched topological susceptibility on a lattice.Comment: 13 pages, LATEX, 3 ps figures, Proc. WORKSHOP ON ETA PHYSICS, Uppsala, October 22-27, 200

Lattice sum rules for the colour fields

We analyse the sum rules describing the action and energy in the colour fields around glueballs, torelons and static potentials.Comment: 9 pages LATEX, (typos corrected, to appear in Phys Rev D

The omega-rho meson mass splitting and mixing from lattice QCD

We compare flavour singlet and non-singlet vector mesons from first principles using lattice QCD. With N_f=2 flavours of light quark, this addresses the omega-rho mass difference. Using maximally twisted-mass lattice QCD, we are able for the first time to determine this mass difference precisely and we compare with experiment. We also discuss omega-rho mixing effects arising within QCD through the u-d quark mass difference.Comment: 12 pages 4 figure