Discovery of the X(3872)meson in 2003 ignited intense interest in exotic(neither qq nor qqq)hadrons,but a cc interpretation of this state was difficult to exclude.An unequivocal exotic was discovered in the Z_(c)(3900...Discovery of the X(3872)meson in 2003 ignited intense interest in exotic(neither qq nor qqq)hadrons,but a cc interpretation of this state was difficult to exclude.An unequivocal exotic was discovered in the Z_(c)(3900)^(+)meson—a charged charmonium-like state.A variety of models of exotic structure have been advanced but consensus is elusive.The grand lesson from heavy quarkonia was that heavy quarks bring clarity.Thus,the recently reported triplet of all-charm tetraquark candidates—X(6600),X(6900),and X(7100)—decaying to J/ψJ/ψ is a great boon,promising important insights.We review some history of exotics,chronicle the road to prospective all-charm tetraquarks,discuss in some detail the divergent modeling of J/ψJ/ψ structures,and offer some inferences about them.These states form a Regge trajectory and appear to be a family of radial excitations.A reported,but unexplained,threshold excess could hint at a fourth family member.We close with a brief look at a step beyond:all-bottom tetraquarks.展开更多
基金supported by the Research Start-Up Funding Project of Nanjing Normal Universitythe National Natural Science Foundation of China(Grant Nos.12075123 and 12061141002)the National Science Research and Development Program of China(Grant No.2023YFA1605804)。
文摘Discovery of the X(3872)meson in 2003 ignited intense interest in exotic(neither qq nor qqq)hadrons,but a cc interpretation of this state was difficult to exclude.An unequivocal exotic was discovered in the Z_(c)(3900)^(+)meson—a charged charmonium-like state.A variety of models of exotic structure have been advanced but consensus is elusive.The grand lesson from heavy quarkonia was that heavy quarks bring clarity.Thus,the recently reported triplet of all-charm tetraquark candidates—X(6600),X(6900),and X(7100)—decaying to J/ψJ/ψ is a great boon,promising important insights.We review some history of exotics,chronicle the road to prospective all-charm tetraquarks,discuss in some detail the divergent modeling of J/ψJ/ψ structures,and offer some inferences about them.These states form a Regge trajectory and appear to be a family of radial excitations.A reported,but unexplained,threshold excess could hint at a fourth family member.We close with a brief look at a step beyond:all-bottom tetraquarks.
