Multi-Pion Systems in Lattice QCD and the Three-Pion Interaction

Abstract

The ground-state energies of 2, 3, 4 and 5 π^+'s in a spatial volume V (2.5 fm)^3 are computed with lattice QCD. By eliminating the leading contribution from three-π^+ interactions, particular combinations of these n-π^+ ground-state energies provide precise extractions of the π^+π^+ scattering length in agreement with that obtained from calculations involving only two π^+'s. The three-π^+ interaction can be isolated by forming other combinations of the n-π^+ ground-state energies. We find a result that is consistent with a repulsive three-π^+ interaction for m_π< 352 MeV.

4 pages, 5 figures