Results on fully charmed tetraquarks at the LHC

Thursday 21 Jul 2022, 15:00 → 16:30 Asia/Shanghai

摘要 Quarks and gluons are elementary particles of nature that participate the strong interaction. How quarks are confined to form matter is a fundamental problem of QCD, the theory for the strong interaction in the Standard Model. The last two decades witnessed observations of new types of hadrons consistent with four or five constituent quarks, which provide new insights into QCD. Among them is the observation of X(6900) by LHCb in 2020 in the di- final state, compatiable with a fully charmed tetraquark . A structure close to di- mass threshold was also reported, however its nature is uncertain in LHCb analysis. Recently, new results on studies of states in di- mass spectrum are reported by ATLAS and CMS collaborations. The X(6900) state is confirmed by both expriments, with similar mass and width measurements. Besides, a new state X(6600) is observed with 5.7 sigma significance, and another new state X(7300) is reported with 4.1 sigma significance. Fully charmed tetraquarks are likely compact objects, in which four charm quarks interact with by exchanging gluons. Other interpretations include hadron molecules where two charmonia are loosely bound with nuclear-like interaction, and coupled multiple di-quarkonia channel rescattering effect. These states provide an ideal place to study the QCD confinement. In this simenar, results of by ATLAS, CMS and LHCb as well as their impact will be discussed.