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arXiv · 1309.2104

The scalar pion form factor in two-flavor lattice QCD

Vera Gülpers·Georg von Hippel·Hartmut Wittig
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Abstract

We calculate the scalar form factor of the pion using two dynamical flavors of non-perturbatively $\mathcal{O}(a)$-improved Wilson fermions, including both the connected and the disconnected contribution to the relevant correlation functions. We employ the calculation of all-to-all propagators using stochastic sources and a generalized hopping parameter expansion. From the form factor data at vanishing momentum transfer, $Q^2=0$, and two non-vanishing $Q^2$ we obtain an estimate for the scalar radius $\left ^π_{_{\rm S}}$ of the pion at one value of the lattice spacing and for five different pion masses. Using Chiral Perturbation Theory at next-to-leading order, we find $\left ^π_{_{\rm S}}=0.635\pm0.016$ fm$^2$ at the physical pion mass (statistical error only). This is in good agreement with the phenomenological estimate from $ππ$-scattering. The inclusion of the disconnected contribution is essential for achieving this level of agreement.

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Vera Gülpers, Georg von Hippel, Hartmut Wittig. 2014-04-11. The scalar pion form factor in two-flavor lattice QCD. https://doi.org/10.1103/physrevd.89.094503

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