Interactions of the doubly charmed state $T_{cc} ^+$ with a hadronic medium

Abstract

The recently observed doubly charmed state T + cc belongs to the family of the multiquark states called exotic hadrons. One of main goals of modern hadron physics is to determine the strucutre of these exotic hadrons. Nucleus-nucleus collisions at the LHC offer a possibility to achieve this goal. The yield of T + cc 's produced at the end of the quark-gluon plasma phase of nuclear collisions is related to the internal structure of the state. However this yield may be affected by the interactions in the hadron gas phase. We investigate the absorption and production processes of this new state in a hadronic medium, considering the reactions T + cc π, T + cc ρ → D ( * ) D ( * ) and the corresponding inverses reactions. We use effective field Lagrangians to account for the couplings between light and heavy mesons. The absorption cross sections are found to be larger than the production ones. We compare our results with the only existing estimate of these quantities, presented in a work of J. Hong, S. Cho, T. Song and S. H. Lee, in which the authors employed the quasi-free approximation. We find cross sections which are one order of magnitude smaller. The subject deserves further investigation.

Multiplicity of the doubly charmed state $T_{cc} ^+$ in heavy-ion collisions

“…Its minimum valence quark content is ccū d. From the data, the binding energy with respect to the D * + D 0 mass threshold and the decay width are estimated to be 273 ± 61 ± 5 +11 −14 keV and 410 ± 165 ± 43 +18 −38 keV, respectively, which are consistent with the expected properties of a T + cc isoscalar tetraquark ground state with J P = 1 + [3][4][5][6][7][8][9][10][11][12][13][14]. Since its detection, many works appeared debating the possible mechanisms of its decay/formation and trying to answer the question of whether it is an extended hadron molecule or a compact tetraquark [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”

“…In this sense, in Ref. [28] we have suggested that a good environment to study the T + cc properties is the one provided by heavy ion collisions (HIC), where a large number of charm quarks is produced. In a typical HIC, there is a phase transition from nuclear matter to the locally thermalized state of deconfined quarks and gluons -the socalled quark-gluon plasma (QGP), which expands, cools down and becomes a gas of hadrons.…”

“…We believe that the subject deserves further discussion. In a recent paper [28], we computed the cross sections of T cc production in reactions such as D ( * ) D ( * ) → T cc π, T cc ρ and its absorption in the corresponding inverse processes. The absorption cross sections were found to be larger than the production ones.…”

“…In Ref. [28] the time evolution of the T cc abundance in the hot hadron gas was not addressed. Thus, in this work we complete the work done in Ref.…”

“…Thus, in this work we complete the work done in Ref. [28]. We calculate the thermally averaged cross sections of T + cc production and absorption, and use them as input to solve the kinetic equation and obtain the time evolution of the T + cc multiplicity.…”