Search for Production of Invisible Final States in Single-Photon Decays of Upsilon(1S)
P. del Amo Sanchez
TL;DR
No evidence for processes in the mass range m(A⁰) ≤ 9.2 GeV and m(χ) ≤ 4.5 GeV is found in the sample of 98 × 10⁶ Υ(2S) decays collected with the BABAR detector and stringent limits on new physics models that contain light dark matter states are set.
Abstract
We search for single-photon decays of the Upsilon(1S) resonance, Upsilon->gamma+invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A0, or a pair of dark matter particles, chi chi-bar. Both A0 and chi are assumed to have zero spin. We tag Upsilon(1S) decays with a dipion transition Upsilon(2S)->pi+pi-Upsilon(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m_A0<=9.2 GeV and m_chi<=4.5 GeV in the sample of 98e6 Upsilon(2S) decays collected with the BaBar detector and set stringent limits on new physics models that contain light dark matter states.