Abstract
We present our results on the electromagnetic form factor of pion over a wide range of $Q^2$ using lattice QCD simulations with Wilson-clover valence quarks and HISQ sea quarks. We study the form factor at the physical point with a lattice spacing $a=0.076$ fm. To study the lattice spacing and quark mass effects, we also present results for 300 MeV pion at two different lattice spacings $a=0.04$ and 0.06 fm. The lattice calculations at the physical quark mass appear to agree with the experimental results. Through fits to the form factor, we estimate the charge radius of pion for physical pion mass to be $\langle r_{\pi}^2 \rangle=0.42(2)~{\rm fm}^2$.
Highlights
Pion is one of the most prominent strongly interacting particles next to the nucleon since it is a Goldstone boson of QCD
In this paper we studied the pion form factor in 2 þ 1 flavor lattice QCD using three lattices spacings a 1⁄4 0.076, a 1⁄4 0.06 and a 1⁄4 0.04 fm
The calculations on the coarsest lattice have been performed with the physical value of the quark masses, while for the finer two lattices the valence pion mass was 300 MeV
Summary
Lattice QCD calculations allow one to obtain the pion form factor from first principles, i.e., without any model dependence, up to relatively large Q2. They will provide an important cross-check for the experimental determinations. [65] that high-precision determinations of the pion form factor and the charge radius have potential to shed light on the discrepancy of hadronic vacuum polarization derived from eþ þ e− → hadron cross sections and lattice calculations [66]. To study quark-mass effect, we perform calculations at the physical pion mass, though at somewhat larger lattice spacing, a 1⁄4 0.076 fm.
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