Ratio of Hadronic Decay Rates of J\psi and \psi(2S) and the \rho\pi Puzzle

TL;DR

This paper investigates the ho extpi puzzle in J extpsi and extpsi(2S) decays, analyzing experimental data and theoretical models, revealing discrepancies with perturbative QCD predictions and highlighting the need for further exploration of decay mechanisms.

Contribution

It provides a detailed analysis of decay rate ratios, compares experimental data with theoretical predictions, and emphasizes the importance of new BES results in understanding the puzzle.

Findings

The ratio of hadronic decay rates differs from naive QCD predictions.

Exclusive decay modes account for a small fraction of total extpsi(2S) decays.

Recent BES data offer crucial tests for theoretical models.

Abstract

The so-called \rho\pi puzzle of J\psi and \psi(2S) decays is examined using the experimental data available to date. Two different approaches were taken to estimate the ratio of J\psi and \psi(2S) hadronic decay rates. While one of the estimates could not yield the exact ratio of \psi(2S) to J\psi inclusive hadronic decay rates, the other, based on a computation of the inclusive ggg decay rate for \psi(2S) (J\psi) by subtracting other decay rates from the total decay rate, differs by two standard deviations from the naive prediction of perturbative QCD, even though its central value is nearly twice as large as what was naively expected. A comparison between this ratio, upon making corrections for specific exclusive two-body decay modes, and the corresponding experimental data confirms the puzzles in J\psi and \psi(2S) decays. We find from our analysis that the exclusively reconstructed hadronic decays of the \psi(2S) account for only a small fraction of its total decays, and a ratio exceeding the above estimate should be expected to occur for a considerable number of the remaining decay channels. We also show that the recent new results from the BES experiment provide crucial tests of various theoretical models proposed to explain the puzzle.