Improved Measurement of the Branching Fraction and Engery Spectrum of eta' from Upsilon(1S) Decays

TL;DR

This paper provides an improved measurement of the eta' meson energy spectrum in Upsilon(1S) decays, challenging existing QCD models and suggesting Standard Model dynamics may not explain high-energy eta' production in B decays.

Contribution

The study offers a more precise eta' energy spectrum measurement in Upsilon(1S) decays and tests gluonic form factor models against the data.

Findings

Perturbative QCD models do not fit the high-energy eta' data.

Standard Model strong interactions likely do not explain large eta' rates in B decays.

Results constrain theoretical models of eta' production.

Abstract

We present an improved measurement of the eta' meson energy spectrum in Upsilon(1S) decays, using 1.2 fb^{-1}} of data taken at the Upsilon(1S) center-of-mass energy with the CLEO III detector. We compare our results with models of eta' gluonic form factor that have been suggested to explain the unexpectedly large B to eta' X_s rate. Models based on perturbative QCD fail to fit the data for large eta' energies, showing that Standard Model strong interaction dynamics is not likely to provide an explanation for the large rate of high energy eta' observed in B decays.