paper

Scattering of two and three physical pions at maximal isospin from lattice QCD

arXiv:2008.03035 · doi:10.1140/epjc/s10052-021-09206-5

Abstract

We present the first direct lattice QCD computation of two- and three- scattering quantities that includes an ensemble at the physical point. We study the quark mass dependence of the two-pion phase shift, and the three-particle interaction parameters. We also compare to phenomenology and chiral perturbation theory (ChPT). In the two-particle sector, we observe good agreement to the phenomenological fits in - and -wave, and obtain at the physical point from a direct computation. In the three-particle sector, we observe reasonable agreement at threshold to the leading order chiral expansion, i.e.\@ a mildly attractive three-particle contact term. In contrast, we observe that the energy-dependent part of the three-particle quasilocal scattering quantity is not well described by leading order ChPT.

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