Hadronic effects on theX(3872)meson abundance in heavy ion collisions

Abstract

We study the hadronic effects on the X(3872) meson abundance in heavy ion collisions. We evaluate the absorption cross sections of the X(3872) meson by pions and rho mesons in the hadronic stage of heavy ion collisions, and further investigate the variation in the X(3872) meson abundance during the expansion of the hadronic matter for its two possible quantum number states; J P = 1 + and 2 − . We show that the absorption cross sections and the time evolution of the X(3872) meson abundance are strongly dependent on the structure and quantum number of the X(3872) meson. We thus suggest that studying the abundance of the X(3872) meson in relativistic heavy ion collisions provides a chance to infer its quantum number as well as its structure.

X(3872)production in high energy heavy ion collisions

“…The coalescence formalism is based on the overlap of the Wigner functions of the quarks and of the bound state, being thus sensitive to the spatial configuration of the charmonium state and hence being able to distinguish between a compact, ≃1 fm long, tetraquark configuration and a large ≃10 fm long, molecular configuration. A big difference between the predicted abundancies could be used as a tool to discriminate between different X structures and to help us to decide whether it is a molecule or a tetraquark [31]. However (as before in the case of the J=ψ) the long lasting hadron gas phase can change the yield coming from the plasma.…”

“…Very recently in Ref. [31] and in Ref. [38], the authors revisited the subject, using this theory of charm meson interactions and including vertices with the X.…”

“…They were used in Ref. [31], where the hadronic absorption cross section of the X by mesons like π and ρ was evaluated for the processes πX → DD, πX → D ÃDÃ , ρX → DD, ρX → DD Ã , and ρX → D ÃDÃ . Using these cross sections, the variation of the X meson abundance during the expansion of the hadronic matter was computed with the help of a kinetic equation with gain and loss terms.…”

“…[31]. The first and most important one is the inclusion of the anomalous vertices πD Ã D Ã and XD Ã D Ã , which were neglected before.…”

Update on J/ψ regeneration in a hadron gas

“…The total number of pions and ρ mesons at freeze-out was taken from Refs. [39,42,43]. In the case of K ( * ) andK ( * ) mesons [40], we work with the assumption that strangeness reaches approximate chemical equilibrium in heavy ion collisions due to the short equilibration time in the quark-gluon plasma and the net strangeness of the QGP is zero.…”