New exotic charmonium states

In the last years many states in the charmonium mass region were discovery by BABAR,Belle and CDF collaborations.I discuss some of these discoveries,and how the QCD Sum Rule approach can be used to understand the structure of these states.     

New exotic charmonium states

In the last years many states in the charmonium mass region were discovery by BABAR, Belle and CDF collaborations. I discuss some of these discoveries, and how the QCD Sum Rule approach can be used to understand the structure of these states.     

Internal motion of massive charmed quarks in double charmonium production in electron-positron annihilation

The cross section for double charmonium production in electron-positron annihilation at the interaction energy of √s = 10.6 GeV is estimated. Both the form of the charmonium wave function and a nonzero charmed-quark mass are taken into account.     

Fine-structure splittings of excited P-and D-wave states in charmonium

It is shown that, in the relativistic case, the fine-structure splittings of the excited 2³ P _J and 3³ P _J states in charmonium are as large as those of the 1³ P _J state if the same value of α_s(μ)≈0.36 is used. The predicted mass of M(2³ P ₀)=3.84 GeV appears to be 120 MeV lower than the center of gravity of the 2³ P _J multiplet and lies below the D $\bar D$ ^* threshold. Our value of M(2³ P ₀) is nearly 80 MeV lower than that from the Godfrey and Isgur article [Phys. Rev. D 32, 189 (1985)], while the differences in other masses are not greater than 20 MeV.     

How to find two more narrow states of charmonium

Two out of the three still missing D-states of charmonium, with masses around 3.8 GeV, are shown to be narrow and detectable in hadronic collisions. They are the J^PC = 2^?? state, to be seen through its decay into ψππ or ψη, and the 2^?+ state with a favoured decay mode ψ3π. Electromagnetic decay modes are also discussed.     

Intermediate annihilation states in antiproton-nucleus scattering

We study the annihilations on nuclei paying special attention to the role of unitarity in these processes. Analysing the intermediate states, it is shown that the annihilation cross section is much larger than the difference $\text{p}\text{?}\text{A ?}\text{p}\text{A}$ and for heavy nuclei is even larger than the non-annihilation cross section. The singular way in which unitarity works in annihilations can be used to test several models of particle-nucleus interactions.     

Formation of charmonium states in heavy-ion collisions and thermalization of charm

We examine the possibility to utilize in-medium charmonium formation in heavy-ion interactions at collider energy as a probe of the properties of the medium. This is possible because the formation process involves recombination of charm quarks which imprints a signal on the resulting normalized transverse momentum distribution containing information about the momentum distribution of the quarks. We have contrasted the transverse momentum spectra of J/ψ, characterized by 〈p _T ²〉, which result from the formation process in which the charm quark distributions are taken at opposite limits with regard to thermalization in the medium. The first uses charm quark distributions unchanged from their initial production in a pQCD process, appropriate if their interaction with the medium is negligible. The second uses charm quark distributions which are in complete thermal equilibrium with the transversely expanding medium, appropriate if a very strong interaction between charm quarks and medium exists. We find that the resulting 〈p _T ²〉 of the formed J/ψ should allow one to differentiate between these extremes, and that this differentiation is not sensitive to variations in the detailed dynamics of in-medium formation. We include a comparison of predictions of this model with preliminary PHENIX measurements, which indicates compatibility with a substantial fraction of in-medium formation.     

Baryon-antibaryon bound states and annihilation

In order to gain some insight into the problem of the widths of quasi-nuclear levels in the $\text{B}\text{B}$ systems, we investigate a simple multichannel model for the influence of decay channels on a bound state. The shift and width of a bound-state level is found to depend strongly not only on the range of the annihilation and the $\text{B}\text{B}$ wave function at small distances but also on the position of the level relative to the thresholds. We point out a new mechanism through which a level in the vicinity of open thresholds can remain narrow even for strong coupling to the decay channels.     

Production of charmonium（like）states in e^＋e^- interactions

We present a search for new charmonium like states in e~ e~- annihilation using the initial-state radiation and the process e~ e~-→J/ψD~(*)~(*).The analyses are based on a huge data sample recorded near theγ(4S)resonance with the Belle detector at the KEKB e~ e~- asymmetric-energy collider.     

D-mesons and charmonium states in hot isospin asymmetric strange hadronic matter

We study the properties of D and [`(D)] \bar{{D}} mesons in hot isospin asymmetric strange hadronic matter, arising due to their interactions with the hadrons in the hyperonic medium. The interactions of D and [`(D)] \bar{{D}} mesons with these light hadrons are derived by generalizing the chiral SU(3) model used for the study of hyperonic matter to SU(4). The nucleons, hyperons, the scalar isoscalar meson, σ and the scalar-isovector meson, d \delta as modified in the strange hadronic matter, modify the masses of D and [`(D)] \bar{{D}} mesons. It is found that, as compared to the [`(D)] \bar{{D}} mesons ([`(D<sup>0</sup>)] \bar{{D^0}}, D <sup>−</sup>), the properties of the D mesons (D <sup>0</sup>, D <sup>+</sup>) are more sensitive to the isospin asymmetry at high densities. On the other hand, the effects of strangeness fraction are found to be more dominant for the [`(D)] \bar{{D}} mesons as compared to the D mesons and these modifications are observed to be particularly appreciable at high densities. We also study the mass modifications of the charmonium states J/ψ, ψ(3686) and ψ(3770) in the isospin asymmetric strange hadronic matter at finite temperatures and investigate the possibility of the decay of the charmonium states into D [`(D)] \bar{{D}} pairs in the hot hadronic medium. The mass modifications of these charmonium states arise due to their interaction with the gluon condensates of QCD, simulated by a scalar dilaton field introduced to incorporate the broken scale invariance of QCD within the effective chiral model. The effects of finite quark masses are taken into account in the trace of the energy momentum tensor in QCD, while investigating the medium modification of the charmonium masses through the modification of the gluon condensate in the medium. We also compute the partial decay widths of the charmonium states to the D [`(D)] \bar{{D}} pairs in the hadronic medium. The strong dependence on density of the in-medium properties of the D, [`(D)] \bar{{D}} and the charmonium states, as well as the partial decay widths of charmonium states to D [`(D)] \bar{{D}} pairs, found in the present investigation, will be of direct relevance in observables like open charm enhancement as well as J/ψ suppression in the compressed baryonic matter (CBM) experiments at the future Facility for Antiproton and Ion Research, GSI, where the baryonic matter at high densities is planned to be produced.     

Production of P-wave charmonium states in two-particle decays of B c mesons

On the basis of the model of hard one-gluon exchange, the two-particle hadronic decays of B _c mesons into S-and P-wave charmonium states, B _c → X _cc π(ρ), are considered at high momentum transfers and in the nonrelativistic approximation. It is shown that the width with respect to B _c-meson decay into S-wave charmonium states is two times greater than the width with respect to B _c-meson decay into P-wave states and that the yield of J/ψ mesons in the cascade processes of B _c-meson decay via the formation and radiative decay of P-wave charmonium states is approximately 8% of the yield of directly produced J/ψ mesons.     

The role of bound states in positronium annihilation

The temperature dependence of the rates of positronium reaction with diamagnetic organic molecules in liquids, and the observed complicated conversive-chemical interaction of positronium with many paramagnetic molecules in the liquid and gas phases lead to the formulation of some general concepts about positronium interaction with quenchers. The positronium and acceptor (Ps-M) complexing is a very essential step of the interaction mechanism. In the case of unstable complexes the contribution of annihilation from the bound state can change depending on the physical conditions of the reaction (pressure in the gas phase, transition from the gas to the liquid phase, heating or replacement of the liquid solvent). The dependence on temperature and on the solvent nature is accounted for by formation of a “bubble” around the positronium in many liquids. At the moment of complexing the “bubble” shrinks with a swiftness depending upon properties of the liquid (surface tension and viscosity). With unstable complexes this leads to complex decomposition and, correspondingly, either to elimination of interaction with the diamagnetic acceptor or, in the case of paramagnetic acceptors, to conversion on the latter, rather than to annihilation from the bound state. With stable complexes further positronium annihilation will occur only from the bound state.