important component of the decay amplitude in all these decays; a more definitive test would involve a direct com- parison of the DP event densities or their two-body pro- jections, as in Fig.3. The χ$_{c}$$_{1}$ case appears to be an exception to this approx- imate agreement, however in view of the large experimen- tal error it is not clear if this is a real discrepancy; theory and experiment only differ by 2 σ . Although the single experimentally unobserved decay η$_{c}$ → p ¯ pπ 0 is predicted by the meson emission model to have a relatively large partial width of 1.7 keV, it is actually considerably suppressed by the presence of an on-diagonal node in the DP event distribution. An experimental study of η$_{c}$ → p ¯ pπ 0 would accordingly be very interesting, since the contributions of other decay mechanisms may be easier to identify in the region of the DP where the meson emission model gives a zero or weak contribution. ψ ′ case has a much larger p ¯ pπ 0 DP area A$_{D}$ than the J/ψ , which is partially compensated by a smaller mean event density 〈 ρ 〉 . (These quantities are given in Ta- ble I.) Using M = 3 . 6861 GeV and the PDG branch- ing fractions B ( ψ ′ → p ¯ pπ $^{0}$) = (1 . 33 ± 0 . 17) · 10 − 4 and B ( ψ ′ → p ¯ p ) = (2 . 75 ± 0 . 12) · 10 − $^{4}$, we find the ψ $^{′}$-based g$_{NNπ}$ estimate This is similar to but somewhat smaller than the estimate obtained above from J/ψ decays (29), and may give an indication of the accuracy of this approach for estimating NNm coupling constants. Of course the other relations for α$_{m}$ analogous to (28) will only be useful if the meson emission decay mech- anism is dominant in those decays as well. Otherwise the contribution of this mechanism to the decay must be identified and quantified, for example through a detailed study of the DP event density. Previously we noted that Ψ → p ¯ pm decays can be used to estimate NNm couplings, provided that the contribu- tion of the meson emission decay mechanism to the de- cay amplitude can be quantified experimentally. In the following we will use the decay J/ψ → p ¯ pπ 0 as an il- lustration of this approach, since the agreement between the experimental and theoretical partial widths suggests that domination of this decay by meson emission is a reasonable first approximation. Since the a priori unknown coupling α$_{J/ψ}$ cancels in the theoretical branching fraction ratio B ( J/ψ → p ¯ pπ $^{0}$) /B ( J/ψ → p ¯ p ), we can use it to estimate g$_{NNπ}$ directly. The meson emission model decay width for Γ( J/ψ → p ¯ pπ $^{0}$) (7) and the two-body decay width (25) imply the following relation between this ratio and the coupling α$_{π}$ ≡ g 2 $_{NNπ}$/ 4 π : Substitution of the experimental PDG numbers B ( J/ψ → p ¯ pπ $^{0}$) = (1 . 09 ± 0 . 09) · 10 − 3 and B ( J/ψ → p ¯ p ) = (2 . 17 ± 0 . 07) · 10 − 3 for these branching fractions leads to the estimate which is consistent with NN meson exchange model val- ues. We expect to find approximately equal g$_{NNπ}$ estimates from other Ψ → p ¯ p and p ¯ pm decay pairs if the me- son emission decay mechanism Ψ → p ¯ p → p ¯ pπ 0 is in- deed dominant. A second state Ψ that can be use to estimate g$_{NNπ}$ is the ψ $^{′}$(3686). Since the ψ ′ has the same quantum numbers as the J/ψ , Eq.(28) is again appropriate for our coupling constant estimate. This The relative theoretical branching fractions (Table II, col.2) suggest that the best channel for identifying a light scalar in Ψ → p ¯ pf$_{0}$ is J/ψ → p ¯ pf$_{0}$ itself (assuming that the meson emission model is a reasonable guide). Given a somewhat larger event sample, ψ ′ → p ¯ pf$_{0}$ should be com- petitive with J/ψ , and has the advantage of more phase Here we will give meson emission model predictions for the branching fractions B (Ψ → p ¯ pf$_{0}$ ), where Ψ = η$_{c}$, J/ψ, χ$_{c}$$_{0}$, χ$_{c}$$_{1}$ and ψ $^{′}$, for a light “sigma” meson with m$_{f}$$_{0}$ = 0 . 5 GeV. To evaluate these partial widths we proceed as in Sec.III.C, and integrate the appropriate decay width formula from the set Eqs.(10-13) over the Dalitz plot. We again use the Ψ p ¯ p coupling constants of Sec.III.C, as given in Table I. The total widths used to convert the calculated partial widths to branching frac- tions are the current PDG values, Γ( η$_{c}$ ) = 27 . 4 MeV, Γ( J/ψ ) = 93 . 2 keV, Γ( χ$_{c}$$_{0}$ ) = 10 . 4 MeV, Γ( χ$_{c}$$_{1}$ ) = 0 . 86 MeV and Γ( ψ $^{′}$) = 309 keV. Our results are given in Table II. Since there is no general agreement re- garding an NNf$_{0}$ (500) coupling constant, in the ta- ble we first give the predicted branching fraction rela- tive to B ( J/ψ → p ¯ pf$_{0}$ (500)) ≡ B$_{0}$ , which is numeri- cally 0 . 338 · 10 − 4 · g 2 $_{NNf$_{0}$}$. (The unknown g$_{NNf}$$_{0}$ can- cels in these ratios.) The next column gives absolute B (Ψ → p ¯ pf$_{0}$ (500)) branching fractions for a rather arbi- trarily chosen g$_{NNf}$$_{0}$ = 10. Finally, the table quotes ex- perimental branching fractions for the related processes Ψ → p ¯ pπ $^{+}$π − for comparison. The long-standing interest in the light scalars makes the possibility of studying them using these decays an attractive prospect. This motivated our inclusion of de- cay formulas for the processes Ψ → p ¯ pf$_{0}$ in our set of theoretical DP event densities. g$_{NNπ}$ ∣ ψ ′ → p ¯ pπ 0 = 9 . 9 ± 0 . 7 . (30) α$_{π}$ = (1 − 4 /R $^{2}$)1 / 2 ( R + 2 /R ) 3 〈 ρ 〉 A$_{D}$/m 4 p · B ( J/ψ → p ¯ pπ $^{0}$) B ( J/ψ → p ¯ p ) . (28) g$_{NNπ}$ ∣ J/ψ → p ¯ pπ 0 = 13 . 3 ± 0 . 6 (29) E. Scalar mesons in Ψ → N ¯ Nm D. g NNπ from B ( J/ψ → p ¯ pπ $^{0}$) /B ( J/ψ → p ¯ p ) 6