Measurement of Interference between Electromagnetic and Strong Amplitudes in psi(2S) Decays to Two Pseudoscalar Mesons

TL;DR

This study measures branching fractions of psi(2S) decays to pseudoscalar mesons, revealing interference effects between electromagnetic and strong decay amplitudes, and extracting their relative phase and strength ratio.

Contribution

It provides the first precise measurements of these branching fractions and the interference parameters for psi(2S) decays to pseudoscalar pairs.

Findings

Branching fraction for psi(2S) -> pi+pi- is less than 2.1 x 10^{-5}.

Measured branching fractions for psi(2S) -> K+K- and KsKl are approximately 6.3 and 5.8 x 10^{-5}.

Determined the relative phase Delta and strength ratio R of decay amplitudes.

Abstract

Using a sample of 3.08 million psi(2S) decays collected at sqrt{s} = 3.686 GeV with the CLEO detector at the Cornell Electron Storage Ring, we have measured the branching fractions for psi(2S) decays to pseudoscalar pairs pi+pi-, K+K-, and KsKl. We obtain B(psi(2S) -> pi+pi-) < 2.1 x 10^{-5} (90% C.L.), B(psi(2S) -> K+K-) = (6.3 +- 0.6(stat) +- 0.3(syst)) x 10^{-5}, and B(psi(2S) -> KsKl) = (5.8 +- 0.8(stat) +- 0.4(syst)) x 10^{-5}. The branching fractions allow extraction of the relative phase Delta = (95 +- 15) degrees and strength ratio R = (2.5 +- 0.4) of the three-gluon and one-photon amplitudes for these modes.