Study of psi' and chi_c decays as feed-down sources of J/psi hadro-production

TL;DR

This paper quantifies the contributions of psi' and chi_c decays to J/psi production in proton-proton collisions, providing essential data for interpreting J/psi suppression in nuclear collisions as a QCD phase transition signature.

Contribution

It offers the first detailed estimation of feed-down fractions from psi' and chi_c decays to J/psi in pp collisions based on global nuclear data and absorption assumptions.

Findings

J/psi feed-down from psi' is approximately 8.1%.

J/psi feed-down from chi_c is approximately 25%.

Results are derived from global averages of proton-nucleus measurements.

Abstract

The interpretation of the J/psi suppression patterns observed in nuclear collisions, at CERN and RHIC, as a signature of the formation of a deconfined phase of QCD matter, requires knowing which fractions of the measured J/psi yields, in pp collisions, are due to decays of heavier charmonium states. From a detailed analysis of the available mid-rapidity charmonium hadro-production cross sections, or their ratios, we determine that the J/psi feed-down contributions from psi' and chi_c decays are, respectively, (8.1 +/- 0.3) % and (25 +/- 5) %. These proton-proton values are derived from global averages of the proton-nucleus measurements, assuming that the charmonium states are exponentially absorbed with the length of matter they traverse in the nuclear targets.