The I  = 1 pion–pion scattering amplitude and timelike pion form factor from N f  = 2 + 1 lattice QCD

Andersen, Christian (CP3-Origins, University of Southern Denmark, Campusvej 55, Odense M, 5230, Denmark) ; Bulava, John  (CP3-Origins, University of Southern Denmark, Campusvej 55, Odense M, 5230, Denmark) ; Hörz, Ben (PRISMA Cluster of Excellence, Institut für Kernphysik, University of Mainz, Johann-Joachim-Becher-Weg 45, Mainz, 55099, Germany) ; Morningstar, Colin (Department of Physics, Carnegie Mellon University, Pittsburgh, PA, 15213, USA)

19 December 2018

Abstract: The elastic I=1 p -wave ππ scattering amplitude is calculated together with the isovector timelike pion form factor using lattice QCD with Nf=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=0.05fm , several pion masses down to mπ=200MeV , and spatial volumes of extent L=3.1–5.5fm . 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.

Published in: Nuclear Physics B 939 (2019) 145-173
Published by: Elsevier
DOI: 10.1016/j.nuclphysb.2018.12.018
License: CC-BY-3.0

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