Isospin0 $\pi\pi$ scattering from twisted mass lattice QCD
Abstract
We present results for the isospin0 $\pi\pi$ swave scattering length calculated in twisted mass lattice QCD. We use three $N_f = 2$ ensembles with unitary pion mass at its physical value, 240~MeV and 330~MeV respectively. We also use a large set of $N_f = 2 + 1 +1$ ensembles with unitary pion masses varying in the range of 230~MeV  510~MeV at three different values of the lattice spacing. A mixed action approach with the OsterwalderSeiler action in the valence sector is adopted to circumvent the complications arising from isospin symmetry breaking of the twisted mass quark action. Due to the relatively large lattice artefacts in the $N_f = 2 + 1 +1$ ensembles, we do not present the scattering lengths for these ensembles. Instead, taking the advantage of the many different pion masses of these ensembles, we qualitatively discuss the pion mass dependence of the scattering properties of this channel based on the results from the $N_f = 2 + 1 +1$ ensembles. The scattering length is computed for the $N_f = 2$ ensembles and the chiral extrapolation is performed. At the physical pion mass, our result $M_\pi a^\mathrm{I=0}_0 = 0.198(9)(6)$ agrees reasonably well with various experimental measurements and theoretical predictions.
 Publication:

arXiv eprints
 Pub Date:
 January 2017
 arXiv:
 arXiv:1701.08961
 Bibcode:
 2017arXiv170108961L
 Keywords:

 High Energy Physics  Lattice
 EPrint:
 7 pages, 2 figures, talk presented at the 34th annual International Symposium on Lattice Field Theory (Lattice2016), 2430 July 2016, University of Southampton, UK