Polarized χ c 2 -charmonium production in antiproton-nucleus interactions

Starting from the Feynman diagram representation of multiple scattering we consider the polarized χc(1P)-charmonia production in antiproton-nucleus reactions close to the threshold (plab=5-7 GeV/c). The rescattering and absorption of the incoming antiproton and outgoing charmonium on nucleons are taken into account, including the possibility of the elastic and nondiagonal (flavor-conserving) scattering χcJN→χcJ′N, J,J′=0,1,2. The elementary amplitudes of the latter processes are evaluated by expanding the physical χc states in the Clebsch-Gordan series of the cc̄ states with fixed values of internal orbital angular momentum (Lz) and spin projections on the χc momentum axis. The total interaction cross sections of these cc̄ states with nucleons have been calculated in previous works using the QCD factorization theorem and the nonrelativistic quarkonium model, and turned out to be strongly Lz dependent due to the transverse size difference. This directly leads to finite values of the χc-nucleon nondiagonal scattering amplitudes. We show that the χc0N→χc2N transitions significantly influence the χc2 production with helicity zero at small transverse momenta. This can serve as a signal in future experimental tests of the quark structure of χc states by the PANDA Collaboration at the Facility for Antiproton and Ion Research (FAIR).