pp annihilation into mesons in flight and at rest are analysed in the constituent quark model with the 3P0 and the 3S1 model for the qq pair creation/annihilation vertex. In the 3P0 model, one assumes that the created/annihilated qq pair has the quantum number of the vacuum, while in the 3S1 model, it has the quantum number of a gluon. As the meson channels we consider combinations of s-wave mesons and p-wave mesons, and in the annihilation into two mesons we compare the annihilation model (A2), the rearrangement model with a 3P0 vertex (R2) and the rearrangement with a 3S1 vertex (S2). The initial state interaction is taken into account by solving the coupled Lippmann-Schwinger equation including virtual NΔ ± NΔ and ΔΔ channels. The combination of R3 and A2 in the 3P0 model roughly reproduces the branching ratios of pp annihilation into mesons, while the combination of R3 and R2 and the combination of R3 and S2 show worse agreement with the experimental branching ratios. The total pp annihilation cross section turned out to be about 60% of the experimental value for R3 + A2 and R3 + R2 and about 70% for R3 + S2, which means that we need other mechanisms of pp annihilation into mesons. The channel of virtual Δ's modifies the branching ratios of certain partial waves, but in the total annihilation cross section, the effect of Δ's is not large.
ASJC Scopus subject areas
- Nuclear and High Energy Physics