Measurement of the branching ratio for Υ(1S) state intoπ ⁺ π ⁻ andsearch for decaysΥ(1S)→π ⁺ π ⁻,K ⁺ K ⁻,p $\bar p$

Abstract

In the experiment withe ⁺ e ⁻-beams performed at the VEPP-4 storage ring with the MD-1 detector we have measuredB _μμ, the branching ratio for the decay of Υ(1S) state intoμ ⁺ μ ⁻. We obtainedB _μμ=(2.12+0.20+0.10)%. It is shown that the continuum and resonance interference should be taken into account. For the first time the upper limits on the branching ratio for the decaysΥ→π ⁺ π ⁻,K ⁺ K ⁻,p $\bar p$ have been measured: Br(Υ→π ⁺ π ⁻)<5·10⁻⁴, Br(Υ→K ⁺ K ⁻)<5·10⁻⁴, Br(Υ→p $\bar p$<9·10⁻⁴ (90% CL).