Multi-quark hadrons from Heavy Ion Collisions

Identifying hadronic molecular states and/or hadrons with multi-quark components either with or without exotic quantum numbers is a long standing challenge in hadronic physics. We suggest that studying the production of these hadrons in relativistic heavy ion collisions offer a promising resolution to this problem as yields of exotic hadrons are expected to be strongly affected by their structures. Using the coalescence model for hadron production, we find that compared to the case of a non-exotic hadron with normal quark numbers, the yield of an exotic hadron is typically an order of magnitude smaller when it is a compact multi-quark state and a factor of two or more larger when it is a loosely bound hadronic molecule. We further find that due to the appreciable numbers of charm and bottom quarks produced in heavy ion collisions at RHIC and even larger numbers expected at LHC, some of the newly proposed heavy exotic states could be produced and realistically measured in these experiments.Comment: 4 pages, 1 figure, revised version to be published in Phys. Rev. Let

Exotics from Heavy Ion Collisions

Discriminating hadronic molecular and multi-quark states is a long standing problem in hadronic physics. We propose here to utilize relativistic heavy ion collisions to resolve this problem, as exotic hadron yields are expected to be strongly affected by their structures. Using the coalescence model, we find that the exotic hadron yield relative to the statistical model result is typically an order of magnitude smaller for a compact multi-quark state, and larger by a factor of two or more for a loosely bound hadronic molecule. We further find that some of the newly proposed heavy exotic states could be produced and realistically measured at RHIC and LHC.Comment: Presented at International Conference on the Structure of Baryons (Baryons '10), Osaka, Japan, Dec.7-11, 201

Studying Exotic Hadrons in Heavy Ion Collisions

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.Comment: 18 pages, 2 figure

Reduction of channel coupling effect on Li isotope elastic scatterings by glue-like behaviour of excess neutron

PROCEEDINGS OF THE 4TH INTERNATIONAL WORKSHOP ON “STATE OF THE ART IN NUCLEAR CLUSTER PHYSICS” (SOTANCP4), 13–18 May 2018, Texas, USA.The glue-like behavior of valence neutrons has been investigated in the Li isotopes. The 7Li nucleus is well known to be weakly bound system with the α + t cluster structure. By adding the valence neutrons, the reduction of the root-mean-square (RMS) radius of the proton density for the 7Li, 8Li and, 9Li nuclei is also well known from the viewpoint of the experimental data and theoretical approach. Elastic scattering cross sections of the Li isotopes on the 12C and 28Si targets at E/A ∼ 50 MeV are calculated. We find the change of the channel coupling (CC) effect on elastic scatterings of such Li isotopes by the glue-like role of the valence neutrons. Finally, we realize that the valence neutrons stabilize the binding of core parts, and the CC effect related the core excitation is indeed reduced

Microscopic global optical potential for nucleon-nucleus systems in the energy range 50-400 MeV

We provide a microscopic global optical potential (MGOP) for nucleon-nucleus (NA) systems in a wide range of nuclear mass numbers (A = 10-276) and incident energies (E = 50-400 MeV). The potential is microscopically constructed based on a single-folding (SF) model with the complex G-matrix interaction. The nuclear densities used in the SF model are generated, in a non-empirical way, from two kinds of microscopic mean-field models: the relativistic-mean-field (RMF) and Skyrme-Hartree-Fock BCS (HF-PBCS) models. We calculate the NA potentials for more than 1000 even-even nuclei with atomic number Z = 6-92, involving proton- and neutron-rich unstable nuclei. We confirm that both the MGOP models well reproduce the available experimental data of the total reaction cross sections, the total neutron cross sections, the elastic-scattering cross sections, the analyzing power, and the spin-rotation function Q. We also calculate the proton scattering cross sections of O-22, O-24, and Ni-56 targets to compare the experimental data and then the cross sections for unknown S-48, Zr-100, and Zr-110 are presented for future measurements. For the sake of convenience, the real and imaginary parts of the central and spin-orbit components of the NA potentials are respectively represented in a linear combination of 12-range Gaussians. They are provided on the website [http://www2.yukawa.kyoto-u.ac.jp/similar to takenori.furumoto/] with a program source file for reconstructing the MGOP

Lambda-Lambda Correlation in Relativistic Heavy Ion Collisions

We investigate Λ − Λ correlation function in relativistic heavy ion collisions to extract their interaction. Using an expanding source model for heavy ion collisions, we disentangle effects of collective expansion and those of the interaction at low relative momenta. Then, we discuss the influence of the feed-down correction for Σ0 decay and indicate the possible existence of a residual correlation at high relative momenta. Consequently, the present STAR data suggest a weakly attractive interaction for the ΛΛ pairs which is represented by the scattering length, 1/a0 < −0.8 fm−1

ΛΛ interaction from relativistic heavy-ion collisions

We investigate the two-particle intensity correlation function of Λ in relativistic heavy-ion collisions. We find that the behavior of the ΛΛ correlation function at small relative momenta is fairly sensitive to the interaction potential and collective flows. By comparing the results of different source functions and potentials, we explore the effect of intrinsic collective motions on the correlation function. We find that the recent STAR data give a strong constraint on the scattering length and effective range of ΛΛ interaction, as -1.8fm⁻¹<1/a0<-0.8fm⁻¹ and 3.5fm<reff<7fm, respectively, if Λ samples do not include the feed-down contribution from long-lived particles. We find that the feed-down correction for Σ⁰ decay reduces the sensitivity of the correlation function to the detail of the ΛΛ interaction. As a result, we obtain a weaker constraint, 1/a0<-0.8 fm⁻¹. Implication for the signal of existence of H-dibaryon is discussed. Comparison with the scattering parameters obtained from the double Λ hypernucleus may reveal in-medium effects in the ΛΛ interaction