Search for a low-mass scalar Higgs boson decaying to a tau pair in single-photon decays of Υ(1S)

Abstract

We search for a low-mass scalar C P -odd Higgs boson, A 0 , produced in the radiative decay of the upsilon resonance and decaying into a τ + τ − pair: Υ ( 1 S ) → γ A 0 . The production of Υ ( 1 S ) mesons is tagged by Υ ( 2 S ) → π + π − Υ ( 1 S ) transitions, using a sample of ( 98.3 ± 0.9 ) × 10 6 Υ ( 2 S ) mesons collected by the BABAR detector. We find no evidence for a Higgs boson in the mass range 3.5 ≤ m A 0 ≤ 9.2 GeV , and combine these results with our previous search for the tau decays of the light Higgs in radiative Υ ( 3 S ) decays, setting limits on the coupling of A 0 to the b ¯ b quarks in the range 0.09-1.9. Our measurements improve the constraints on the parameters of the next-to-minimal-supersymmetric Standard Model and similar theories with low-mass scalar degrees of freedom.