Phase difference between the electromagnetic and strong amplitudes for ψ(2S) and J/ψ decays into pairs of pseudoscalar mesons

Using the data for 24.5×106 ψ(2S) produced in e ⁺e ^- annihilations at √s=3686MeV at the CESR-c e ⁺e ^- collider and 8.6×106J/ψ produced in the decay ψ(2S)→π ⁺π ^-J/ψ, the branching fractions for ψ(2S) and J/ψ decays to pairs of pseudoscalar mesons, π ⁺π ^-, K ⁺K ^-, and K _SK _L, have been measured using the CLEO-c detector. We obtain branching fractions B(ψ(2S)→π ⁺π ^-)= (7.6±2.5±0.6)×10 ^-6, B(ψ(2S)→K ⁺K ^-)=(74.8±2.3±3.9)×10 ^-6, B(ψ(2S)→K _SK _L)=(52.8±2.5±3.4) ×10 ^-6, and B(J/ψ→π ⁺π ^-)=(1. 47±0.13±0.13)×10 ^-4, B(J/ψ→K ⁺K ^-)=(2.86±0.09±0.19)×10 ^-4, B(J/ψ→K _SK _L)=(2.62±0.15±0.14) ×10 ^-4, where the first errors are statistical and the second errors are systematic. The phase differences between the amplitudes for electromagnetic and strong decays of ψ(2S) and J/ψ to 0 ^-+ pseudoscalar pairs are determined by a Monte Carlo method to be δ(ψ(2S) _PP=(110.5-9.5+16.0)° and δ(J/ψ) _PP=(73.5-4.5+5.0)°. The difference between the two is Δδδ(ψ(2S)) _PP-δ(J/ψ) _PP=(37.0-10.5+16.5)°.