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

The I = 2 vvelastic s- wave scattering phase shift is measured by lattice quantum chromodynamics with N f = 3 flavors of the Asqtad-improved staggered fermions. The lattice-calculated energy-eigenvalues of vv systems at one center of mass frame and some moving frames using the moving wall source technique are utilized to secure phase shifts by L & uuml;scher'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 a approximate to 0.12 fm, L3T 3 T = 32364), 3 64), two fine (a a approximate to 0.09 fm, L3T 3 T = 40396) 3 96) and a superfine (a a approximate to 0.06 fm, L3T 3 T = 483144) 3 144) lattice ensembles at four pion masses of m v similar to 247 MeV, 249 MeV, 275 MeV, and 384 MeV, respectively.