Observation of an exotic narrow doubly charmed tetraquark

Abstract

Conventional, hadronic matter consists of baryons and mesons made of three quarks and a quark–antiquark pair, respectively1,2. Here, we report the observation of a hadronic state containing four quarks in the Large Hadron Collider beauty experiment. This so-called tetraquark contains two charm quarks, a $$\overline{{{{{u}}}}}$$ u ¯ and a $$\overline{{{{{d}}}}}$$ d ¯ quark. This exotic state has a mass of approximately 3,875 MeV and manifests as a narrow peak in the mass spectrum of D0D0π+ mesons just below the D*+D0 mass threshold. The near-threshold mass together with the narrow width reveals the resonance nature of the state.

Compositeness of S-wave weakly-bound states from next-to-leading order Weinberg’s relations

“…We also note that, while here r ph is small and positive, the experimental value for the effective range obtained in Ref. [18] is large and negative. However, in the latter work, the negative value is a built-in property of the model used in the analysis.…”

“…The T + cc state has been recently discovered by the LHCb collaboration [17,18] as a prominent peak in the D 0 D 0 π + spectrum. It is very close to the D * + D 0 threshold, since the experimental analysis throw (61) keV [17] or M T + cc = −360(40) keV [18].…”

“…The T + cc state has been recently discovered by the LHCb collaboration [17,18] as a prominent peak in the D 0 D 0 π + spectrum. It is very close to the D * + D 0 threshold, since the experimental analysis throw (61) keV [17] or M T + cc = −360(40) keV [18]. 4 However, the D * 0 D + threshold is only 1.4 MeV above, and therefore one must consider coupled channels in order to have a fully accurate description of the state.…”

“….) have reported the observation of a plethora of unstable states and peaks in mass-distributions located surprisingly a e-mail: Miguel.Albaladejo@ific.uv.es (corresponding author) b e-mail: jmnieves@ific.uv.es close to different two bottomed/charmed-hadron thresholds, such as the XY Z mesons, the P c pentaquarks [8][9][10][11][12][13][14][15][16], or the doubly charmed T + cc state [17,18]. There exist also clear examples of exotic candidates in the open charm and bottom sectors, e.g.…”

“…We assume that the T + cc state is mostly an isoscalar state, as suggested by additional experimental information besides the D 0 D 0 π + spectrum, see Refs [17,18,76]…”