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Paper IPM / Physic / 15090  


Abstract:  
The structure, spectroscopic parameters and width of the resonance with quantum numbers
J^{PC}=1^{++} discovered by the COMPASS Collaboration and classified as
the a_{1}(1420) meson are examined in the context of QCD sum rule
method. In the calculations the axialvector meson a_{1}(1420) is
treated as a fourquark state with the diquarkantidiquark structure. The
mass and current coupling of a_{1}(1420) are evaluated using QCD twopoint
sum rule approach. Its observed decay mode a_{1}(1420) → f_{0}(980)π, and
kinematically allowed ones, namely a_{1} → K^{∗±}K^{±}, a_{1} →K^{∗0} ―K^{0} and a_{1} → ―K^{∗0} K^{0} channels are
studied employing QCD sum rules on the lightcone. Our prediction for the
mass of the a_{1}(1420) state m_{a1}=1416_{−79}^{+81} MeV is
in excellent agreement with the experimental result. Width of this state Γ = 145.52 ±20.79 MeV within theoretical and experimental
errors is also in accord with the COMPASS data.
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