Quark disconnected diagrams in chiral perturbation theory
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We show how quark-disconnected and quark-connected contributions to hadronic n-point functions can be written as independent correlators for which one can derive expressions in partially quenched chiral effective theory. As an example we apply the idea to the case of the hadronic vacuum polarisation. In particular, we consider the cases of the Nf = 2 theory without and with a partially quenched strange quark and also the Nf= 2+ 1 theory. In the latter two cases a parameter-free prediction for the disconnected contribution at NLO in the effective theory is given. Finally we show how twisted boundary conditions can then be used in lattice QCD to improve the q2 resolution in the connected contributions even when flavour singlet operators are considered.
KeywordsLattice QCD Nonperturbative Effects Electromagnetic Processes and Properties Chiral Lagrangians
- M. Della Morte, B. Jäger, A. Jüttner and H. Wittig, in preparation.Google Scholar
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