Search for a low-mass Higgs boson in Y(3S)-->gamma A^0, A^0-->tau^+tau^- at BABAR

Abstract

We search for a light Higgs boson, $A^0$, in the radiative decay $Υ(3S)\toγA^0$, $A^0\toτ^+τ^-$, $τ^+\to e^+ν_e \barν_τ$ or $τ^+\to μ^+ ν_μ \barν_τ$. The data sample contains 122 million $Υ(3S)$ events recorded with the \babar detector. We find no evidence for a narrow structure in the studied $τ^+τ^-$ invariant mass region of $4.03<m_{τ^+τ^-}<10.10$ \gevcc. We exclude at the 90% confidence level (C.L.) a low mass Higgs decaying to $τ^+τ^-$ with a product branching fraction ${\cal {B}}(Υ(3S)\toγA^0)\times {\cal {B}}(A^0\toτ^+τ^-)$ $>(1.5-16)\times 10^{-5}$ across the $m_{τ^+τ^-}$ range. We also set a 90% C.L. upper limit on the $τ^+τ^-$-decay of the $η_b$ at ${\mathcal{B}}(η_b\to τ^+τ^-)<8%$.