Upsilon(1S)->gamma+f2'(1525); f2'(1525)->K0sK0s decays

TL;DR

This paper reports the first evidence of the decay Upsilon(1S) to gamma and f2'(1525) via K0sK0s, measuring its rate and comparing it with related decays to test theoretical predictions.

Contribution

It provides the first evidence for Upsilon(1S) decaying into gamma and f2'(1525) with K0sK0s, and compares the branching ratio with J/psi decays to evaluate theoretical models.

Findings

Measured branching fraction: (4.0±1.3±0.6)×10^{-5}

Branching ratio ratio: 0.09±0.02

Consistent with soft collinear effective theory expectations

Abstract

We report on a study of exclusive radiative decays of the Upsilon(1S) resonance into a final state consisting of a photon and two K0s candidates. We find evidence for a signal for Upsilon(1S)->gamma f_2'(1525); f_2'(1525)->K0sK0s, at a rate (4.0+/-1.3+/-0.6)x10^{-5}, consistent with previous observations of Upsilon(1S)->gamma f_2'(1525); f_2'(1525)->K+K-, and isospin. Combining this branching fraction with existing branching fraction measurements of Upsilon(1S)->gamma f_2'(1525) and J/psi->gamma f_2'(1525), we obtain the ratio of branching fractions: B(Upsilon(1S)->gamma f_2'(1525))/B(J/psi->gamma f_2'(1525))=0.09+/-0.02, approximately consistent with expectations based on soft collinear effective theory.