Abstract
We report on the status of the determination of properties of flavour-singlet pseudoscalar mesons using Wilson twisted mass lattice QCD at maximal twist. As part of project C7 , a large number of phenomenologically relevant quantities could be extracted from first principle, from η and η′ masses to decay widths of pseudoscalar mesons to two photons.
Highlights
In the early days of the theory of strong interactions, the peculiar mass hierarchy found experimentally for the nine light pseudoscalar mesons led to the formulation of the “U(1) problem” [1]
We report on the status of the determination of properties of flavour-singlet pseudoscalar mesons using Wilson twisted mass lattice QCD at maximal twist
With automatic O(a) improvement being the biggest advantage of twisted mass lattice QCD at maximal twist, the downside is that flavour symmetry is broken at finite values of the lattice spacing
Summary
In the early days of the theory of strong interactions, the peculiar mass hierarchy found experimentally for the nine light pseudoscalar mesons led to the formulation of the “U(1) problem” [1]. If the axial U(1) symmetry was spontaneously broken in the SU(3) chiral limit of QCD, one would expect the ninth pseudoscalar meson to have a mass similar or a bit lighter than the kaons and the η meson. In the DFG funded project within the collaborative research centre CRC16 “Subnuclear Structre of Matter” we could increase the available lattice results in the flavoursinglet pseudoscalar sector significantly. This was possible on the one hand due to the lattice discretisation we are using: the Wilson twisted mass formulation at maximal twist is well suited to study η and η mesons because of a powerful noise reduction method we developed in Ref. The results presented in the remaining sections represent an summary, update and extension of what was published in Refs. [10,11,12,13,14,15]
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