Speaker
Dr
Mikhail Barabanov
(Joint Institute for Nuclear Research)
Description
The study of strong interactions and hadronic matter in the process of antiproton-proton annihilation seems to be a challenge nowadays. The research of charmonium (the system consisting of charmed quark-antiquark pair cc\bar), charmed hybrids (the system consisting of charmed quark-antiquark pair strongly interacting with gluonic component cc\barg) spectra and their main characteristics: mass, width and branch ratios in experiments using antiproton beam with momentum ranging from 1 to 15 GeV/c at FAIR, are promising to understand the dynamics of quark interactions at small distances. Charmonium spectroscopy is a good testing tool for the theories of strong interactions: QCD in both perturbative and non-perturbative regimes, QCD inspired purely phenomenological potential models, non-relativistic QCD and LQCD.
A possibility to study the charmonium spectrum and exotic states with the hidden charm in PANDA experiment at FAIR is considered. The reactions of antiprotons impinging on the proton or nuclear targets embedded in the High Energy Storage Ring will be studied in these experiments. The elaborate analysis of charmonium and charmed hybrid spectrum is carried out, and the attempts to interpret a great quantity of experimental data over DD\bar - pair are considered. But much more data on different decay modes are needed for a deeper analysis. These data can be derived directly from PANDA experiment with its high quality antiproton beam. The advantage of antiproton beam consists in intensive production of particle-antiparticle pairs which is observed in antiproton-proton annihilation. This fact allows one to carry out spectroscopic research with good statistics and high accuracy. Hence, there is a possibility of measuring the masses, widths and branch ratios of different charmonium and charmed hybrid states with high accuracy.
Nowadays the scalar 1P1(hc), 1D2 and vector 3PJ(χ0,1,2), 3DJ - charmonium states and higher laying scalar 1S0(ηс) and vector 3S1(ψ) – charmonium states are poorly investigated. The domain over - threshold of 3.73 GeV/c2 is poorly studied. According to the contemporary quark models (LQCD, flux tube model), namely in this domain, the existence of charmed hybrids with exotic (JPC = 0+-, 1-+, 2+-) as with non-exotic (JPC=0-+, 1+-,2-+, 1++, 1--) quantum numbers is expected.
During the last several years nearly twenty new states (particles) with the hidden charm were discovered by different experimental groups. Their interpretation is ambiguous nowadays. Most of these states were observed over the DD\bar - threshold in some definite channel (beside X(3872)-state). New particles were produced from B-meson decays and in electron-positron or two-photon collisions.
The authors have proposed a combined approach based on the quarkonium potential model and relativistic top model for decay products to calculate the mass spectrum of radial excited states of charmonium and of charmed hybrids. One assumes that the decay potential has the finite radius beyond which the decaying charmonium or charmed hybrid are considered as collection of two relativistic tops in the same quantum state.
The most interesting decay channels of charmonium (from theoretical and experimental viewpoints) pp\bar → cc\bar → ρπ, pp\bar → cc\bar → \Sigma0 \Sigma0\bar and decays into DD\bar - pair and decays with J/Ψ in the final state pp\bar → J/Ψ + X, were, in particular, considered. The masses of the particles participating in charmonium formation and decay are known with high precision. The mass spectra of the radial excited scalar and vector charmonium states and partially charmed hybrids were calculated in the framework of the combined approach up to the B-meson mass range. The results of the calculations have coincided with the existing experimental data within the experimental error. The existence of new states of charmonium and charmed hybrids over DD\bar - pair is expected. It was shown that some of the new states (recently discovered by experimental groups Belle, BaBar, CLEO, CDF) can be interpreted as higher laying scalar and vector radial excited states of charmonium. This treatment needs to be carefully verified in the future PANDA experiment. All charmonium states can be directly formed in pp\bar - annihilations through the coherent annihilation of three quarks in the proton with three antiquarks in the antiproton. With this method their masses and widths can be measured with excellent accuracy, determined by the precise knowledge of the initial pp\bar - state and not limited by the resolution of the detector. It becomes possible to extract the information about the excited states of charmonium in these experiments which can be extremely useful to study the strong coupling nature. Using the integral approach, the widths of the expected states of charmonium were calculated. It has been demonstrated that widths of the predicted charmonium states are also narrow and don’t have anomalous large values.
Primary author
Dr
Mikhail Barabanov
(Joint Institute for Nuclear Research)
Co-authors
Prof.
Alexander Vodopyanov
(Joint Institute for Nuclear Research)
Dr
Valery Dodokhov
(Joint Institute for Nuclear Research)
