This paper reports a combined analysis of data from the three large LHC experiments — LHCb, ATLAS and CMS — that strengthens evidence for a particle-like structure near 7.2 GeV/c2 called X(7200) and gives more precise properties for a previously seen structure called X(6900). The authors fit the published di‑J/ψ mass spectra, where J/ψ is a well-known particle made of a charm quark and a charm antiquark. The X(6900) is seen with very high significance (greater than 12 standard deviations). Signals consistent with X(7200) appear in several fit versions, with significance ranging from 3.7σ to 6.6σ; the most favorable fit gives 6.6σ.

What the researchers did is a simultaneous statistical fit to the mass distributions reported by the three experiments. They tested four different hypotheses for how peaks add together. Some fits treat resonances as independent peaks. Others allow coherent interference, meaning the quantum amplitudes for overlapping states add with phases and can shift or reshape the observed peaks. The fits also include two sources of background called single‑parton scattering (SPS) and double‑parton scattering (DPS). The authors account for the different mass resolutions of the experiments, which are much better for LHCb (below 5 MeV/c2) than for ATLAS or CMS.

At a high level, the work shows that interference effects matter a lot when extracting the masses and widths of these structures. Earlier individual measurements gave different values depending on the model. For example, CMS found that including interference could shift the X(6900) mass by roughly 80 MeV and increase its width by a factor of about 1.6. By fitting all data together and testing multiple interference scenarios, the authors obtain improved precision for X(6900) and stronger evidence for X(7200) under some models.

Why this matters: these structures are candidates for “fully‑charmed tetraquarks,” exotic states made of four charm quarks. Such systems are interesting because they do not contain light quarks and so offer a cleaner way to study the strong force (Quantum Chromodynamics) in a regime where calculations are difficult. More precise experimental information helps theorists decide whether the peaks are compact tetraquarks, threshold effects from other processes, or something else.