Φπ production in anti pp annihilation from S and P states and in J/ψ decays

Recent experiments at LEAR have found surprisingly large branching ratios for reactions anti NN → φπ from S-wave initial states while no φπ production is observed from P states of the pp system. Also, no φπ is seen in radiative J/ψ decays even though the rate for ωπ is substantial. We calculate the φπ production rates for these three cases via K K* intermediate states and K K rescattering using the dispersion relation technique; we find that the large φπ rate in pp annihilations from S states can be reproduced with a reasonable cut-off for the dispersion integral; for J/ψ decays the calculated φπ rate is compatible with the observed upper limit. We would, however, expect φπ to be seen from pp P-states, in contrast to experimental findings. Yet the branching ratio for anti pp → K* anti K via isospin I = 1 of pp, 1P1 state is not known; and therefore no definite conclusion can be drawn. We also compare the Dalitz plots we obtain for direct φ production and for φ production via rescattering. Clear differences between the two theoretical distributions are observed; yet very high precision data would be required to establish the origin - direct production or rescattering - of the φ mesons. This observation supports the use of the isobar model in data analyses. (orig.)