I=2 ππ s -wave scattering length from lattice QCD

Abstract

The I=2 ππ elastic s-wave scattering phase shift is measured by lattice quantum chromodynamics with Nf=3 flavors of the Asqtad-improved staggered fermions. The lattice-calculated energy-eigenvalues of ππ systems at one center of mass frame and some moving frames using the moving wall source technique are utilized to secure phase shifts by Lüscher’s formula. Our computations are fine enough to obtain threshold parameters: scattering length a, effective range r, and shape parameter P, which can be extrapolated at the physical point by next-to-leading order in chiral perturbation theory, and our relevant next-to-next-to-leading order predictions from expanding nuclear physics with lattice quantum chromo dynamics collaboration’s works are novelly considered as the systematic uncertainties. Our outcomes are consistent with Roy equation determinations, newer experimental data, and lattice estimations. Numerical computations are performed with a coarse (a≈0.12 fm, L3T=32364), two fine (a≈0.09 fm, L3T=40396) and a superfine (a≈0.06 fm, L3T=483144) lattice ensembles at four pion masses of mπ∼247 MeV, 249 MeV, 275 MeV, and 384 MeV, respectively. Published by the American Physical Society 2024