Studies of exotic hadrons by high-energy exclusive reactions

We investigate the possibility of clarifying internal structure of exotic hadrons by high-energy exclusive reactions. In particular, the constituent-counting rule could be used for determining the internal configuration in large-angle exclusive scattering. As an example, we show the cross section pi^- + p -> K^0 + Lambda(1405) in comparison with the one for the ground-state Lambda production pi^- + p -> K^0 + Lambda. The counting rule indicates that the cross section scales as s^8 dsigma /dt=constant if Lambda(1405) is an ordinary three-quark baryon, whereas it is s^{10} dsigma /dt=constant if Lambda(1405) is a five-quark baryon. Here, s and t are Mandelstam variables. Such experiments could be possible at J-PARC, LEP, JLab, CERN-COMPASS, and other high-energy facilities.