Lattice QCD study of mixed systems of pions and kaons

The different ground-state energies of N-pion and M-kaon systems for N + M <= 12 are studied in lattice QCD. These energies are then used to extract the various two-and three-body interactions that occur in these systems. Particular attention is paid to additional thermal states present in the spectrum because of the finite temporal extent. These calculations are performed using one ensemble of 2 + 1 flavor anisotropic lattices with a spatial lattice spacing a(s) similar to 0.125 fm, an anisotropy factor xi = a(s)/a(t) = 3.5, and a spatial volume L-3 similar to (2.5 fm)(3). The quark masses used correspond to pion and kaon masses of m(pi) similar to 383 MeV and m(K) similar to 537 MeV, respectively. The isospin and strangeness chemical potentials of these systems are found to be in the region where chiral perturbation theory and hadronic models predict a phase transition between a pion-condensed phase and a kaon-condensed phase.