Open charm effects in the explanation of the long-standing "$\rho\pi$ puzzle"

TL;DR

This paper investigates how open charm effects and interference phenomena explain the violations of the 12% rule and helicity selection rule in certain J/psi decay channels, providing a detailed analysis of these non-perturbative contributions.

Contribution

It introduces a comprehensive analysis of open charm threshold effects and their interference with short-distance amplitudes to explain longstanding puzzles in J/psi decays.

Findings

Open charm effects significantly influence decay amplitudes.

Interference between different contributions can violate pQCD rules.

Destructive interference explains deviations from the 12% rule.

Abstract

A detailed analysis of the open charm effects on the decays of $J/\psi(\psi^\prime)\to VP$ is presented, where $V$ stands for light vector meson and $P$ for light pseudoscalar meson. These are the channels that the so-called "12% rule" of perturbative QCD (pQCD) is obviously violated. Nevertheless, they are also the channels that violate the pQCD helicity selection rule (HSR) at leading order. In this work, we put constraints on the electromagnetic (EM) contribution, short-distance contribution from the $c\bar{c}$ annihilation at the wavefunction origin, and long-distance contribution from the open charm threshold effects on these two decays. We show that interferences among these amplitudes, in particular, the destructive interferences between the short-distance and long-distance strong amplitudes play a key role to evade the HSR and cause the significant deviations from the pQCD expected "12% rule".