Proton-antiproton annihilation in the quark model

Abstract

The non-relativistic Quark Model is used to describe the proton-antiproton annihilation and scattering. We investigate which of the diagrams is dominant in the annihilation into three and two mesons. A very sensitive test for the dominance of the different rearrangement and annihilation diagrams is the annihilation into p-wave mesons. Different mechanisms for the annihilation/creation of a quark-antiquark pair are studied. The data clearly prefer the non-perturbative annihilation/ creation into or out of the vacuum ( 3P 0) compared to the annihilation/ creation into a gluon ( 3S 1). For the initial proton-antiproton state, we include the coupling to the delta and antidelta degrees of freedom. For the distortion of the initial state we use one of the one-meson exchange Bonn potentials applying G parity. The imaginary part is calculated from the annihilation into two and three mesons. A comparison with the data shows clearly that the non perturbative annihilation diagrams into two and three mesons are the dominant ones. This is also consistent with the observation that the non-perturbative annihilation of a quark-antiquark pair into the vacuum is stronger than the perturbative annihilation or creation into or out of a gluon. The agreement with the branching ratios of the proton-antiproton decay into mesons and the description of the proton-antiproton scattering and charge exchange cross sections is good.