First Observation of Upsilon(3S) --> tau tau and Tests of Lepton Universality in Upsilon Decays

TL;DR

This paper reports the first observation of Upsilon(3S) decaying into tau pairs, tests lepton universality in Upsilon decays, and measures branching ratios, providing insights into potential new physics like a low mass CP-odd Higgs boson.

Contribution

It provides the first observation of Upsilon(3S) to tau tau decay and precise measurements of branching ratios, testing lepton universality in bottomonium decays.

Findings

First observation of Upsilon(3S) to tau tau decay

Branching ratios consistent with lepton universality

Set limits on low mass CP-odd Higgs influence

Abstract

Using data collected with the CLEO-III detector at the CESR e+e- collider, we report on a first observation of the decay of the Upsilon(3S) to tau tau, and precisely measure the ratio of branching fractions of Upsilon(nS),n=1,2,3 to tau tau and mu mu final states, finding agreement with expectations from lepton universality. We derive absolute branching fractions for these decays, and also set a limit on the influence of a low mass CP-odd Higgs boson in the decay of the Upsilon(1S).