2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/37848The 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 with the CLEO III detector. The branching fraction B(Y(1S) -> mu+ mu-) = (2.49 +- 0.02 +- 0.07)% is consistent with the current world average but B(Y(2S) -> mu+ mu-) = (2.03 +- 0.03 +- 0.08)% and B(Y(3S) -> 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.Talk presented at the 1st Meeting of the APS Topical Group on Hadronic Physics (Fermilab, Oct 24-26, 2004). LaTeX 4 pages, 2 figuresHigh Energy Physics - Experimenttext