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Title: The I=2 ππ S-wave Scattering Phase Shift from Lattice QCD

The π+π+ s-wave scattering phase-shift is determined below the inelastic threshold using Lattice QCD. Calculations were performed at a pion mass of mπ ≈ 390 MeV with an anisotropic nf = 2+1 clover fermion discretization in four lattice volumes, with spatial extent L ≈ 2.0, 2.5, 3.0 and 3.9 fm, and with a lattice spacing of bs ≈ 0.123 fm in the spatial direction and bt bs/3.5 in the time direction. The phase-shift is determined from the energy-eigenvalues of π+π+ systems with both zero and non-zero total momentum in the lattice volume using Luscher's method. Our calculations are precise enough to allow for a determination of the threshold scattering parameters, the scattering length a, the effective range r, and the shape-parameter P, in this channel and to examine the prediction of two-flavor chiral perturbation theory: mπ2 a r = 3+O(mπ2χ2). Chiral perturbation theory is used, with the Lattice QCD results as input, to predict the scattering phase-shift (and threshold parameters) at the physical pion mass. Our results are consistent with determinations from the Roy equations and with the existing experimental phase shift data.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [3] ;  [2] ;  [4] ;  [6] ;  [7]
  1. Albert Einstein Zentrum fur Fundamentale Physik, Sidlerstrasse (Switzerland); Univ. of New Hampshire, Durham (New Hampshire)
  2. Univ. of Barcelona (Spain)
  3. Jefferson Lab., Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States)
  4. Univ. of Washington, Seattle, WA (United States)
  5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  6. Indiana Univ., Bloomington, IN (United States)
  7. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
OSTI Identifier:
1035545
Report Number(s):
JLAB-THY--11-1381; DOE/OR/23177--1643; arXiv:1107.5023
Journal ID: ISSN 1550-7998; TRN: US1201148
Grant/Contract Number:
AC05-06OR23177; AC02-05CH11231; FC02- 07ER41457; AC52-07NA27344; FC02-06ER41443; FG02-07ER41527; FG02-04ER41302; FG03- 97ER4014; AC02- 06CH11357)
Type:
Accepted Manuscript
Journal Name:
Physical Review. D, Particles, Fields, Gravitation and Cosmology
Additional Journal Information:
Journal Volume: 85; Journal Issue: 3; Journal ID: ISSN 1550-7998
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Contributing Orgs:
NPLQCD Collaboration
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CLOVER; FERMIONS; FORECASTING; PERTURBATION THEORY; PHASE SHIFT; PIONS; QUANTUM CHROMODYNAMICS; SCATTERING; SCATTERING LENGTHS