Search for a Light Higgs Boson and Low Mass Dark Matter at the Belle Experiment

Abstract

We report a search for a light CP-odd Higgs boson A0, which can be produced in U decays and decay to low mass dark matter, c. We search for evidence of the on-shell process, U(1S) ! gA0,A0 ! cc, and the off-shell process, U(1S) ! gcc, via the dipion transition U(2S) ! U(1S)p+p􀀀. We present the first Belle search for final states with a single photon and missing energy in the mass range of MA0 < 9.0 GeV/c2 and Mc < 4.5 GeV/c2 with a data sample of 157.3 106 U(2S) decays. We find no evidence for a signal and set limits on branching fractions for such processes. We also use the limit on the off-shell process to set competitive limits on WIMP-nucleon scattering cross sections.