Variational study of the flux tube recombination in the two quarks and   two quarks system in Lattice QCD
  The color fields in a system composed by two static quarks and two static antiquarks are studied. In particular, we consider the four particles in the corners of a rectangle, and two possible alignment of the particles, one in which the quarks are at the same side of the rectangle, and the other where they are at opposite sides. We use a variational method, to probe not only the ground state but also the first excited state. This results permit us to observe and interpret the flux-tube recombination in the mesons to mesons and the tetraquark to mesons transitions, for both states. The results are compared with previous results for the static potential and the Casimir scaling predictions. 
M. Cardoso, N. Cardoso, P. Bicudo
hep-lat hep-ph