Abstract
The associated production of a J/ψ and a π meson in antiproton–nucleon annihilation is studied in the framework of QCD collinear factorization. In this approach, a hard subprocess responsible for the production of the heavy quark–antiquark pair factorizes from soft hadronic matrix elements, such as the antiproton (nucleon) distribution amplitude and the nucleon-to-pion (antiproton-to-pion) transition distribution amplitude. This reaction mechanism should dominate the forward and backward kinematical regions, where the cross sections are expected to be measurable in the set-up of the P̄ANDA experiment at the GSI-FAIR facility.
Highlights
The factorization of exclusive amplitudes in a short distance dominated part which may be calculated in a perturbative way in the one hand, and universal confinement related hadronic matrix elements in the other hand, is a welcome feature of quantum chromodynamics (QCD) for specific processes in specific kinematics
The validity of such a factorization requires at least the existence of a large scale Q, which has been taken as the spacelike, respectively timelike, virtuality of the photon quantifying the electromagnetic probe in the case of electroproduction, respectively lepton pair emission in antinucleon-nucleon annihilation
In this Letter we address the reaction p + N → J/ψ + π which will be studied in the PANDA experiment at GSI-FAIR to look for exotic charmonium states production [27]
Summary
The factorization of exclusive amplitudes in a short distance dominated part which may be calculated in a perturbative way in the one hand, and universal confinement related hadronic matrix elements in the other hand, is a welcome feature of quantum chromodynamics (QCD) for specific processes in specific kinematics. The extension of this description to other processes such as backward virtual Compton scattering and backward meson electroproduction, has been advocated [1, 2, 3] - not proven In the latter process, new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes (TDAs), appear which shed a new light on the nucleon structure, and enable to quantify nucleon’s mesonic cloud. New hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes (TDAs), appear which shed a new light on the nucleon structure, and enable to quantify nucleon’s mesonic cloud The validity of such a factorization requires at least the existence of a large scale Q, which has been taken as the spacelike, respectively timelike, virtuality of the photon quantifying the electromagnetic probe in the case of electroproduction, respectively lepton pair emission in antinucleon-nucleon annihilation. Our aim is to single out with the help of factorization techniques the perturbative part of the process and to relate the remaining non-perturbative part to universal fundamental quantities with interpretation within QCD as the light-cone matrix elements of correlators of the fundamental fields
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