Production of exotic tetraquarks QQq¯q¯ in heavy-ion collisions at the LHC

Abstract

We investigate the production of exotic tetraquarks, QQqq ≡ T QQ (Q = c or b and q = u or d), in relativistic heavy-ion collisions using the quark coalescence model. The T QQ yield is given by the overlap of the density matrix of the constituents in the emission source with the Wigner function of the produced tetraquark. The tetraquark wave function is obtained from exact solutions of the four-body problem using realistic constituent models. The production yields are typically one order of magnitude smaller than previous estimations based on simplified wave functions for the tetraquarks. We also evaluate the consequences of the partial restoration of chiral symmetry at the hadronization temperature on the coalescence probability. Such effects, in addition to increasing the stability of the tetraquarks, lead to an enhancement of the production yields, pointing towards an excellent discovery potential in forthcoming experiments. We discuss further consequences of our findings for the search of exotic tetraquarks in central Pb+Pb collisions at the LHC.

Tetra- and Penta-Quark Structures in the Constituent Quark Model

“…However, the other one is 190 MeV above the B −B * 0 theoretical threshold. Our result on this diquark-antidiquark bound state is supported by references [26][27][28]34], and only ∼130 MeV lower than the calculated value in reference [27].…”

“…Furthermore, the double-bottom tetraquark state with I(J P ) = 0(1 + ) is also predicted by a relativistic quark model [33]. Reference [34] gives some indications on where to find it in heavy-ion collisions at the LHC. For the antiparticle case, thebbud bound state is stable against strong decays, Lattice QCD [35] predicted a mass of 10476 ± 24 ± 10 MeV and spin-parity J P = 1 + .…”

Double-heavy tetraquarks

“…The obtained deeply bound state ðbbÞ Ã ðūdÞ at 10261 MeV is supported by Refs. [52,53,55,56], only ∼130 MeV lower than the predicted mass in Ref. [53].…”

“…[54]. A compact double-bottom tetraquark state with IJ P ¼ 01 þ is also presented in heavy-ion collisions at the LHC [55], and actually, in 1988, the dimeson TðbbūdÞ had already been proposed [56]. Besides, a narrow ðbbÞðūdÞ diquark-antidiquark state with IJ P ¼ 01 þ is predicted in Ref.…”

QQs¯s¯ tetraquarks in the chiral quark model

“…Moreover, within the one-boson-exchange model, possible triple-charm molecular pentaquarks Ξ cc D ðÃÞ are suggested [51]. In the tetraquark sector, double-heavy tetraquarks are studied using QCD sum rules [52], quark models [53,54] and even lattice-regularized QCD computations [55]. Besides, theoretical techniques such as diffusion Monte Carlo [56], Bethe-Salpeter equation [57], QCD sum rules [58,59] and effective phenomenological models [60][61][62][63][64] have recently contributed to the investigations of fully heavy tetraquarks QQQQ.…”