24–25 Jun 2017
Hong Kong University of Science and Technology (HKUST)
Asia/Hong_Kong timezone

Observation of a Baryonium Candidate at BES

25 Jun 2017, 11:10
5m
Hong Kong University of Science and Technology (HKUST)

Hong Kong University of Science and Technology (HKUST)

Speaker

Tianjue Min

Description

Baryonium (proton-antiproton bound state) was predicted by theory long ago but not confirmed in experiment. In this talk, we will give a brief review of observation of a baryonium candidate at the BESII and BESIII experiments. Using 58 million J/psi decay events, the BESII experiment observed the proton-antiproton mass threshold enhancement X(ppbar) in J/psi->gamma p pbar and the X(1835) in J/psi->gamma eta' pi+ pi-. Many theorists believe these two states are two different manifestations of a baryonium state. But due to the limit of statics, no affirmative conclusion can be made. With huge J/psi data sample collected at the BESIII experiment, the spins and parities of X(ppbar) and X(1835) were both determined to be 0-+. Also with this huge data sample, the BESIII experiment firstly established the direct connection between the X(ppbar) and the X(1835) and the the new observation supports the existence of a proton-antiproton bound state or molecule like state with significance larger than 7 sigma.

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