Measurment of the Muonic Branching Fraction of the Narrow Upsilon Resonances at CLEO

TL;DR

This paper measures the muonic decay branching fractions of narrow Upsilon resonances at CLEO, finding larger values for Y(2S) and Y(3S) than previously reported, which impacts their total decay widths.

Contribution

It provides new measurements of the muonic branching fractions for Y(2S) and Y(3S) resonances, revealing larger values than prior results and refining their decay width estimates.

Findings

B(Y(1S) to mu+mu-) = (2.49 +- 0.02 +- 0.07)%

B(Y(2S) to mu+mu-) = (2.03 +- 0.03 +- 0.08)%

B(Y(3S) to mu+mu-) = (2.39 +- 0.07 +- 0.10)%

Abstract

The decay branching fractions of the three narrow Upsilon resonances to mu+mu- have been measured by analyzing about 4.3 1/fb e+e- data collected in the vicinity of the resonances with the CLEO III detector. The branching fraction B(Y(1S) to mu+mu-) = (2.49 +- 0.02 \+- 0.07)% is consistent with the current world average but B(Y(2S) to mu+mu-) = (2.03 +- 0.03 +- 0.08)% and B(Y(3S) to mu+mu-) = (2.39 +- 0.07 +- 0.10)% are significantly larger than prior results. These new muonic branching fractions imply a narrower total decay width for the Y(2S) and Y(3S) resonances and lower other branching fractions that rely on these decays in their determination.