PT Journal
AU Fischer, M
   Kostrzewa, B
   Liu, LM
   Romero-Lopez, F
   Ueding, M
   Urbach, C
TI Scattering of two and three physical pions at maximal isospin from lattice QCD Extended Twisted Mass Collaboration
SO European Physical Journal C
JI Eur. Phys. J. C
PY 2021
BP 436 - 19pp
VL 81
IS 5
DI 10.1140/epjc/s10052-021-09206-5
LA English
AB We present the first direct N-f = 2 lattice QCD computation of two- and three-pi(+) scattering quantities that includes an ensemble at the physical point. We study the quark mass dependence of the two-pion phase shift, and the three-particle interaction parameters. We also compare to phenomenology and chiral perturbation theory (ChPT). In the two-particle sector, we observe good agreement to the phenomenological fits in s- and d-wave, and obtain M(pi)a(0) = -0.0481(86) at the physical point from a direct computation. In the three-particle sector, we observe reasonable agreement at threshold to the leading order chiral expansion, i.e. a mildly attractive three-particle contact term. In contrast, we observe that the energy-dependent part of the three-particle quasilocal scattering quantity is not well described by leading order ChPT.
ER