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arXiv · 1808.05007

The $I=1$ pion-pion scattering amplitude and timelike pion form factor from $N_{\rm f} = 2+1$ lattice QCD

Christian Andersen·John Bulava·Ben Hörz·Colin Morningstar
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Abstract

The elastic $I=1$ $p$-wave $ππ$ scattering amplitude is calculated together with the isovector timelike pion form factor using lattice QCD with $N_{\rm f}=2+1$ dynamical quark flavors. Wilson clover ensembles generated by the Coordinated Lattice Simulations (CLS) initiative are employed at four lattice spacings down to $a = 0.05\,\mathrm{fm}$, several pion masses down to $m_π = 200\,\mathrm{MeV}$, and spatial volumes of extent $L = 3.1-5.5\,\mathrm{fm}$. The set of measurements on these ensembles, which is publicly available, enables an investigation of systematic errors due to the finite lattice spacing and spatial volume. The $ππ$ scattering amplitude is fit on each ensemble by a Breit-Wigner resonance lineshape, while the form factor is described better by a thrice-subtracted dispersion relation than the Gounaris-Sakurai parametrization.

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Christian Andersen, John Bulava, Ben Hörz, Colin Morningstar. 2018-12-17. The $I=1$ pion-pion scattering amplitude and timelike pion form factor from $N_{\rm f} = 2+1$ lattice QCD. https://doi.org/10.1016/j.nuclphysb.2018.12.018

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