Search for di-muon decays of a low-mass Higgs boson in radiative decays of the Υ(1S)

We search for di-muon decays of a low-mass Higgs boson (A0) produced in radiative Υ(1S) decays. The Υ(1S) sample is selected by tagging the pion pair in the Υ(2S,3S)→π+π-Υ(1S) transitions, using a data sample of 92.8×106 Υ(2S) and 116.8×106 Υ(3S) events collected by the BABAR detector. We find no evidence for A0 production and set 90% confidence level upper limits on the product branching fraction B(Υ(1S)→γA0)×B(A0→μ+μ-) in the range of (0.28-9.7)×10-6 for 0.212≤mA0≤9.20  GeV/c2. The results are combined with our previous measurements of Υ(2S,3S)→γA0, A0→μ+μ- to set limits on the effective coupling of the b quark to the A0.