Observation of a family of all-charm tetraquarks at CMS

The CMS experiment reports the observation of three structures in the JpsiJpsi to four muon channel — X(6600), X(6900), and X(7100) — each with a significance well above 5 sigma, confirming and extending the earlier Run 2 results. Strong interference effects among them, also above 5 sigma, indicate they share the same quantum numbers. A complementary search in the JpsiPsi2S channel reveals two structures consistent with X(6900) and X(7100). A spin–parity analysis favors a JPC=2++ assignment, a rare quantum number among known hadrons. Together, these findings strongly support the interpretation of these states as a family of all-charm tetraquarks, offering new insights into the dynamics of exotic resonances.