Exotic hadrons in heavy ion collisions

Abstract

We investigate the possibilities of using measurements in present and future experiments on heavy ion collisions to answer some longstanding problems in hadronic physics, namely identifying hadronic molecular states and exotic hadrons with multiquark components. The yields of a selected set of exotic hadron candidates in relativistic heavy ion collisions are discussed in the coalescence model in comparison with the statistical model. We find that the yield of a hadron is typically an order of magnitude smaller when it is a compact multiquark state, compared to that of an excited hadronic state with normal quark numbers. We also find that some loosely bound hadronic molecules are formed more abundantly than the statistical model prediction by a factor of two or more. Moreover, due to the significant numbers of charm and bottom quarks produced at RHIC and even larger numbers expected at LHC, some of the proposed heavy exotic hadrons could be produced with sufficient abundance for detection, making it possible to study these new exotic hadrons in heavy ion collisions.

Exotic tetraquark states with the $$qq\bar{Q}\bar{Q}$$ q q Q ¯ Q ¯ configuration

“…energy for the production of a ssbb (sscb) at an electron-positron collider should be √ s > 22 ( √ s > 15) GeV. Of these exotic states, the production of the lowest T cc at various facilities (Tevatron, RHIC, LHC, KEK) has been considered [38][39][40][71][72][73][74]. Because of its clean background, the electron-positron collision experiment has its advantage in searching for T cc .…”

Update on J/ψ regeneration in a hadron gas

“…We shall make use of the evolution equation for the abundances of particles included in processes discussed above. The momentum-integrated evolution equation has the form [37][38][39][40][41] …”

“…We will assume that π,ρ,K,K * ,D, and D * are in equilibrium. Therefore, the density n i (τ ) can be written as [37][38][39][40][41] …”

“…This number can be calculated with perturbative QCD and yields the charm quark fugacity factor γ C in Eq. (16) [37][38][39][40][41]. 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.…”