Phase Difference Between the Electromagnetic and Strong Amplitudes for psi(2S) and J/psi Decays into Pairs of Pseudoscalar Mesons

TL;DR

This study measures decay branching fractions and phase differences between electromagnetic and strong decay amplitudes for psi(2S) and J/psi into pseudoscalar meson pairs, using large datasets from the CLEO-c detector.

Contribution

It provides the first precise measurements of phase differences between electromagnetic and strong decay amplitudes for psi(2S) and J/psi into pseudoscalar mesons.

Findings

Measured branching fractions for psi(2S) and J/psi decays to pseudoscalar pairs.

Determined phase differences between electromagnetic and strong decay amplitudes.

Found a significant phase difference of about 37 degrees between psi(2S) and J/psi decays.

Abstract

Using the data for 24.5x10^6 psi(2S) produced in e^+e^- annihilations at sqrt{s}=3686 MeV at the CESR-c e^+e^- collider and 8.6x10^6 J/psi produced in the decay psi(2S)->pi^+pi^-J/psi, the branching fractions for psi(2S) and J/psi decays to pairs of pseudoscalar mesons, pi^+pi^-, K^+K^-, and K_S K_L, have been measured using the CLEO-c detector. We obtain branching fractions Br(psi(2S)->pi^+pi^-)=(7.6+-2.5+-0.6)x10^-6, Br(psi(2S)->K^+K^-)=(74.8+-2.3+-3.9)x10^-6, Br(psi(2S)->K_S K_L)=(52.8+-2.5+-3.4)x10^-6, and Br(J/psi->pi^+pi^-)=(1.47+-0.13+-0.13)x10^-4, Br(J/psi->K^+K^-)=(2.86+-0.09+-0.19)x10^-4, Br(J/psi+-K_S K_L)=(2.62+-0.15+-0.14)x10^-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 psi(2S) and J/psi to 0^{-+} pseudoscalar pairs are determined by a Monte Carlo method to be \delta(psi(2S)_{PP}=(110.5^{+16.0}_{-9.5})^o and \delta(J/psi)_{PP}=(73.5^{+5.0}_{-4.5})^o. The difference between the two is \Delta\delta = \delta(psi(2S))_{PP}-\delta(J/psi)_{PP} =(37.0^{+16.5}_{-10.5})^o.