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APPLICATION OF HIGH QUALITY ANTIPROTON BEAM WITH MOMENTUM
RANGING FROM 1 TO 15 GeV/c TO STUDY CHARMONIUM AND EXOTICS
OVER DD
-THRESHOLD
M.Yu. Barabanov, A.S. Vodopyanov
Veksler-Baldin Laboratory of High Energy Physics
Joint Institute for Nuclear Research
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, charmed hybrids spectra and their
main characteristics (mass, width and branch ratios) in experiments using antiproton beam with
momentum ranging from 1 GeV/c to 15 GeV/c, 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, LQCD and QCD inspired
phenomenological potential models.
Nowadays the scalar 1 P 1 , 1 D 2 and vector 3 P J , 3 D J , - charmonium states and higher laying scalar 1 S 0
and vector 3 S 1 – charmonium states are poorly investigated. The domain over DD
- threshold of 3.73
GeV/c 2 is badly studied. According to the contemporary quark models (LQCD, flux tube model),
namely in this domain, the existence of charmed hybrids with exotic (J PC = 0 +- , 1 -+ , 2 +- ) as with nonexotic
(J PC =0 -+ , 1 +- ,2 -+ , 1 ++ , 1 -- ) quantum numbers is expected.
The elaborate analysis of charmonium spectrum was carried out, and the attempts to interpret a great
quantity of experimental data over DD
- pair were considered. The decays into DD
pair, into light
mesons and decays with J/Ψ or Ψ' in the final state were considered. Using the combined approach
based on the quarkonium potential model and confinement model on a three-dimensional sphere
embedded into the four-dimensional Euclidian space, new charmonium states in the mass region over
DD
-threshold equal to 3.73 GeV/c are expected to exist. But much more data on different decay
modes (decay channels) are needed for 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 states with high accuracy.
The elaborated analysis of spectrum of charmed hybrids with exotic and non-exotic quantum
numbers in the mass region mainly over DD
-threshold is given. Different decay modes of charmed
hybrids such as decays into charmonium and light mesons in the final state and decays into DD
* -pair
(S-wave plus P-wave mesons) were, in particular, considered. These modes possess small widths and
significant branch fractions. This fact facilitates their experimental detection. Using the combined
approach based on the quarkonium potential model and confinement model on a three-dimensional
sphere embedded into the four-dimensional Euclidian space, the spectrum of lowest-laying
charmonium hybrids over DD
-threshold was calculated. The necessity of further study of
charmonium hybrids and their main characteristics (mass, width, branch ratios) in PANDA experiment
was demonstrated.
Especial attention is given to the new states with the hidden charm discovered recently ( XYZparticles).
The experimental data from different collaborations Belle, BaBar, CLEO, CDF were
carefully studied. Most of these states were observed over D D - threshold in one definite channel.
New particles were produced from B-meson decays and in electron-positron or two-photon collisions.
Their interpretation is far from been obvious nowadays. Therefore many recently discovered states
above the DD
- threshold expect their verification and explanation. Some of these states can be
interpreted as higher laying radial excited states of charmonium. This treatment seems to be
perspective and needs to be carefully verified in the future PANDA experiment at FAIR.
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