Study of the doubly charmed tetraquark $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$

Abstract

Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D0D0π+ mass spectrum just below the D*+D0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + tetraquark with a quark content of $${{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}\overline{{{{{{\rm{u}}}}}}}\overline{{{{{{\rm{d}}}}}}}$$ c c u ¯ d ¯ and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*+ mesons is consistent with the observed D0π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.

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

“…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]…”

Doubly Heavy Tetraquarks in the Chrial Quark Soliton Model

“…Recent discovery of a doubly charmed tetraquark T + cc with mass ∼ 3875 MeV, approximately ∼ 300 keV below the D * + D 0 threshold, by the LHCb Collaboration [1,2] triggered a number of theoretical studies of exotic heavylight states. A comprehensive review of multiquark states, both experimental and theoretical, before T + cc discovery can be found in Ref.…”