Special Seminar: Search for Light Higgs and Low Mass Dark Matter at Belle, and Commissioning of Belle II

 

ATLAS and CMS have discovered the Standard Model (SM) Higgs boson; nevertheless, many questions about the SM still remain. The NMSSM, a scenario for physics beyond the SM, can be a path to resolving some of these questions. The NMSSM scenario predicts seven Higgs bosons. The lightest CP-odd Higgs boson, A0, can be produced in radiative Y (b-bbar bound state) decays and decay to low mass dark matter (DM). Using the high statistics datasets of the Belle experiment at the KEKB electron-positron collider in Japan, I search for evidence of on-shell and off-shell production of the A0 in Y(1S) decays. I will present the first Belle search for final states with a single photon and missing energy in the mass range MA0 < 9.2 GeV and MDM < 4.5 GeV. Additionally, the implication of our results for direct dark matter searches will be discussed.

This talk will also describe Time Projection Chamber (TPC) detectors used in Belle II and SuperKEKB commissioning. SuperKEKB will deliver 40 times higher instantaneous luminosity than KEKB, which can generate severe beam backgrounds. The TPC detectors are used for directional detection of fast neutrons induced by beam backgrounds. Recently, we completed the first SuperKEKB commissioning phase. I will present the design and results of the TPC detectors in the first commissioning.