title: Isoscalar ππ Scattering and the σ Meson Resonance from QCD.
abstract: We present for the first time a determination of the energy dependence of the isoscalar ππ elastic scattering phase shift within a first-principles numerical lattice approach to QCD. Hadronic correlation functions are computed including all required quark propagation diagrams, and from these the discrete spectrum of states in the finite volume defined by the lattice boundary is extracted. From the volume dependence of the spectrum, we obtain the S-wave phase shift up to the KK[over ¯] threshold. Calculations are performed at two values of the u, d quark mass corresponding to m_{π}=236,391  MeV, and the resulting amplitudes are described in terms of a σ meson which evolves from a bound state below the ππ threshold at the heavier quark mass to a broad resonance at the lighter quark mass.
authors.affiliation: Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA.
authors.forename: Raul A
authors.initials: RA
authors.lastname: Briceño
authors.affiliation: Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA.|Department of Physics, College of William and Mary, Williamsburg, Virginia 23187-8795, USA.
authors.forename: Jozef J
authors.initials: JJ
authors.lastname: Dudek
authors.affiliation: Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Edwards
authors.affiliation: Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Wilson