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arXiv · 1701.04250

The pseudoscalar meson electromagnetic form factor at high $Q^2$ from full lattice QCD

J. Koponen·A. C. Zimermmane-Santos·C. T. H. Davies·G. P. Lepage·A. T. Lytle
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Abstract

We give an accurate determination of the vector (electromagnetic) form factor, $F(Q^2)$, for a light pseudoscalar meson up to squared momentum transfer $Q^2$ values of 6 $\mathrm{GeV}^2$ for the first time from full lattice QCD, including $u$, $d$, $s$ and $c$ quarks in the sea at multiple values of the lattice spacing. Our results show good control of lattice discretisation and sea quark mass effects. We study a pseudoscalar meson made of valence $s$ quarks but the qualitative picture obtained applies also to the $\pi$ meson, relevant to upcoming experiments at Jefferson Lab. We find that $Q^2F(Q^2)$ becomes flat in the region between $Q^2$ of 2 $\mathrm{GeV}^2$ and 6 $\mathrm{GeV}^2$, with a value well above that of the asymptotic perturbative QCD expectation, but well below that of the vector-meson dominance pole form appropriate to low $Q^2$ values. Our calculations show that we can reach higher $Q^2$ values in future to shed further light on where the perturbative QCD result emerges.

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J. Koponen, A. C. Zimermmane-Santos, C. T. H. Davies, G. P. Lepage, A. T. Lytle. 2017-01-16. The pseudoscalar meson electromagnetic form factor at high $Q^2$ from full lattice QCD. https://doi.org/10.1103/physrevd.96.054501

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