Amplitude Analysis of Di-Charmonium Resonances in Three Decay Channels

Two narrow resonant structures at 6.9 and 7.2 GeV, as well as a broad structure near the di- J 1pt / 1pt ψ production threshold, have recently been observed by the LHCb [1], ATLAS [2], and CMS [3] collaborations in the di- J 1pt / 1pt ψ and J 1pt / 1pt ψ + ψ (2S) invariant-mass spectra with four muons in the final state. This suggests the existence of fully heavy tetraquark candidates with a ccc̄c̄ quark configuration: $$X(6900)$$ , $$X(7200)$$ , and $$X(6500)$$ . However, their quantum properties have not yet been confirmed [4]. This report presents an amplitude analysis for the di- J 1pt / 1pt ψ and J 1pt / 1pt ψ + ψ (2S) channels with 4μ and 4μ + 2π in final states, aimed at studying the properties of these exotic resonances. By performing a simultaneous fit to the mass and angular distributions, the masses and widths of the observed structures are determined under the hypothesis of two interfering states with JP = 0⁺ for both. The comparisons with other spin–parity hypotheses for $$X(6900)$$ are also presented.