First observation of psi(2S)-->K_S K_L

TL;DR

This paper reports the first observation of the decay psi(2S) to K_S K_L, measuring its branching ratio and analyzing its implications for quantum chromodynamics and decay amplitude phases.

Contribution

It presents the first measurement of the psi(2S) to K_S K_L decay and explores its impact on understanding decay mechanisms in charmonium states.

Findings

Branching ratio B(psi(2S)-->K_S K_L) = (5.24±0.47±0.48)×10^{-5}

Enhanced decay rate compared to J/psi-->K_S K_L

Insights into the phase between three-gluon and one-photon decay amplitudes

Abstract

The decay psi(2S)-->K_S K_L is observed for the first time using psi(2S) data collected with the Beijing Spectrometer (BESII) at the Beijing Electron Positron Collider (BEPC); the branching ratio is determined to be B(psi(2S)-->K_S K_L) = (5.24\pm 0.47 \pm 0.48)\times 10^{-5}. Compared with J/psi-->K_S K_L, the psi(2S) branching ratio is enhanced relative to the prediction of the perturbative QCD ``12%'' rule. The result, together with the branching ratios of psi(2S) decays to other pseudoscalar meson pairs (\pi^+\pi^- and K^+K^-), is used to investigate the relative phase between the three-gluon and the one-photon annihilation amplitudes of psi(2S) decays.