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

Abstract

We search for di-muon decays of a low-mass Higgs boson ( A 0 ) produced in radiative Υ ( 1 S ) decays. The Υ ( 1 S ) sample is selected by tagging the pion pair in the Υ ( 2 S , 3 S ) → π + π − Υ ( 1 S ) transitions, using a data sample of 92.8 × 10 6 Υ ( 2 S ) and 116.8 × 10 6 Υ ( 3 S ) events collected by the BABAR detector. We find no evidence for A 0 production and set 90% confidence level upper limits on the product branching fraction B ( Υ ( 1 S ) → γ A 0 ) × B ( A 0 → μ + μ − ) in the range of ( 0.28 − 9.7 ) × 10 − 6 for 0.212 ≤ m A 0 ≤ 9.20 GeV / c 2 . The results are combined with our previous measurements of Υ ( 2 S , 3 S ) → γ A 0 , A 0 → μ + μ − to set limits on the effective coupling of the b quark to the A 0 .