Study of psi(2S) Decays to gamma p bar{p}, pi^0 p bar{p} and eta p bar{p} and Search for p bar{p} Threshold Enhancements

TL;DR

This study investigates psi(2S) decays into various baryon-antibaryon and meson states, measuring branching fractions and searching for p p̄ threshold enhancements, confirming previous findings in J/psi decays but not in psi(2S).

Contribution

First detailed analysis of psi(2S) decays into gamma, pi^0, and eta p p̄ channels with evidence for N* and f_2 resonances, and a comparison to J/psi decay results.

Findings

Measured branching fractions for psi(2S) decays.

Evidence for N* and f_2 resonances.

No p p̄ threshold enhancement in psi(2S) decays.

Abstract

The decays of psi(2S) into gamma p bar{p}, pi^0 p bar{p} and eta p bar{p} have been studied with the CLEO-c detector using a sample of 24.5 million psi(2S) events obtained from e^+e^- annihilations at sqrt{s} = 3686 MeV. The data show evidence for the excitation of several N^* resonances in p pi^0 and p eta channels in pi^0 p bar{p} and eta p bar{p} decays, and f_2 states in gamma p bar{p} decay. Branching fractions for decays of psi(2S) to gamma p bar{p}, pi^0 p bar{p} and eta p bar{p} have been determined. No evidence for p bar{p} threshold enhancements was found in the reactions psi(2S)-> X p bar{p}, where X = gamma, pi^0, eta. We do, however, find confirming evidence for a p bar{p} threshold enhancement in J/psi-> gamma p bar{p} as previously reported by BES.