Gluonic Structures of Tetraquarks
  We formulate quantitative flux-tube overlap functions to account for the nonperturbative gluonic behaviors. In order to deduce systematic functional form, we introduce connection amplitude which can be defined between two boundary points occupied by quark or antiquark. With the deduced flux-tube overlap function, we can figure out long range gluonic structures of various quark combinations. In this paper, we report our calculated results for tetraquarks, $q^2 \bar{q}^2$, by considering two different configurations of boundary points for possible explanations of X(3872). 
Jin Dong Kim, Su Kyoung Lee, Jong B. Choi