What do we learn from the ρ-π puzzle

  • The experimental observation indicates that the branching ratio of ψ´→ρπ is very small while the ρ-π channel is a main one in J/ψ decays. To understand the puzzle, various interpretations have been proposed. Meanwhile according to the hadronic helicity selection rule, this decay mode should be suppressed. Numerical calculations are needed to determine how it is suppressed. We calculate the branching ratios of J/ψ→ρπ and ππ in the framework of QCD. The results show that the branching ratios are proportional to (mu+md/MJ/ψ)2 for the ρπ mode and (mu+md/MJ/ψ)2 for the ππ mode which is isospin violated. The theoretical prediction of the ratio of J/ψ→ρπ is smaller than data, but not too small to invoke a completely new mechanism. Thus the puzzle is still standing even though we learn much knowledge towards the puzzle and this will help to finally interpret the puzzle and then gain a deeper insight to the heavy quarkonia.

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  • [1] . Rosner J L. Phys. Rev. D, 2001, 64: 0940022. Suzuki M. Phys. Rev. D, 2001, 63: 054021, hep-ph/00062963. LI X Q, Bugg D V, ZOU B S. Phys. Rev. D, 1997, 55: 14214. LIU X, ZENG X, LI X. Phys. Rev. D, 2006, 74: 0740035. LI G, LI T, LI X, MA W. Nucl. Phys. B, 2008, 727: 301;LI T, ZHAO S, LI X. Nulc. Phys. A, 2009, 828: 1256. Brodsky S, Lepage G. Phys. Rev. D, 1981, 24: 2848; Bram-billa N et al. Heavy Quarkonium Physics, hep-ph/04121587. MO X H, YUAN C Z, WANG P. arXiv:hep-ph/06112148. ZHAO Q, LI G, CHANG C H. Phys. Lett. B, 2007, 645:173; LI G, ZHAO Q, CHANG C H. J. Phys. G, 2008, 35:055002; ZHAO Q. Talk given at "The Conference on Inter-disciplinary Fields of Particle Physics, Nuclear Physics and Cosmology", Tenchong, Yunnan, China, Aug. 2 to 4
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Get Citation
LI Xue-Qian. What do we learn from the ρ-π puzzle[J]. Chinese Physics C, 2010, 34(2): 267-269. doi: 10.1088/1674-1137/34/2/022
LI Xue-Qian. What do we learn from the ρ-π puzzle[J]. Chinese Physics C, 2010, 34(2): 267-269.  doi: 10.1088/1674-1137/34/2/022 shu
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Received: 2009-09-02
Revised: 2009-09-25
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What do we learn from the ρ-π puzzle

    Corresponding author: LI Xue-Qian,
  • Department of Physics, Nankai University, Tianjin 300071, China

Abstract: 

The experimental observation indicates that the branching ratio of ψ´→ρπ is very small while the ρ-π channel is a main one in J/ψ decays. To understand the puzzle, various interpretations have been proposed. Meanwhile according to the hadronic helicity selection rule, this decay mode should be suppressed. Numerical calculations are needed to determine how it is suppressed. We calculate the branching ratios of J/ψ→ρπ and ππ in the framework of QCD. The results show that the branching ratios are proportional to (mu+md/MJ/ψ)2 for the ρπ mode and (mu+md/MJ/ψ)2 for the ππ mode which is isospin violated. The theoretical prediction of the ratio of J/ψ→ρπ is smaller than data, but not too small to invoke a completely new mechanism. Thus the puzzle is still standing even though we learn much knowledge towards the puzzle and this will help to finally interpret the puzzle and then gain a deeper insight to the heavy quarkonia.

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