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Resent BES Results on Scalar Mesons

Resent BES Results on Scalar Mesons. Zhipeng Zheng (Representing BES Collaboration) Institute of High Energy Physics, CAS GHP-2004, Oct. 25. OUTLINE. Introduction  and  f 0 (980) f 0 (1370) , f 0 (1500) , f 0 (1710) and f 0 (1790) Summary. Introduction (1).

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Resent BES Results on Scalar Mesons

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  1. Resent BES Results on Scalar Mesons Zhipeng Zheng (Representing BES Collaboration) Institute of High Energy Physics, CAS GHP-2004, Oct. 25

  2. OUTLINE • Introduction •  and  • f0(980) • f0(1370), f0(1500), f0(1710)and f0(1790) • Summary

  3. Introduction(1) Why are light scalar mesons interesting? • The knowledge on the light scalars is very important to the understanding of QCD in nonperturbative region • There have been hot debates on the existence of and  .

  4. Introduction(2) • f0(980): precise parameters m,  …. are needed. Is it a state, or molecular or four quark state? • Lattice QCD predicts the 0++ scalar glueball mass from 1.5 - 1.7 GeV. f0(1500) and f0(1710) are good candidates.

  5. Introduction(3) • f0(1370), f0(1500), f0(1710)were found in the fixed target, , e+e- experiments. The confirmation of them is important. • f0(1500), f0(1710) are treated as mixed state of glueball with meson, but we need more information. • The BESII data have much higher statistics and lead to a much more decisive partial wave analysis.

  6. Introduction(4) World J/ and (2S) Samples (×106) BESII Detector BESII 58MJ/ J/ BESII 14M(2S) • VC: xy = 100 m TOF: T = 180 ps • MDC: xy = 220 m BSC: E/E= 21 % • dE/dx= 8.5 %  = 7.9 mr • p/p=1.78(1+p2) z = 2.3 cm • counter: r= 3 cm B field: 0.4 T z = 5.5 cm (2S)

  7. The  pole in J/+-  0 M() M(+-0) f2(1270)   M(+-) f2(1270)

  8. Fit Method I: (whole mass region) Channels fitted to the data: J/f2(1270)  f0(980) b1(1235) ’(1450) f2(1565) f2(2240) b1(1235) f2 contribution f0 contribution

  9. Fit Method II: (M<1.5GeV) Fit to J/→+ (M < 1.5 GeV) f2 contribution f0 contribution Channels fitted to the data: J/f2(1270)  f0(980) b1(1235) P.S

  10. Breit-Wigner for  in the fit: (1) (2) (3) (4)

  11. Fit Result Method I Method II Averaged pole position: P. L. B 598 (2004) 149-158

  12.  in J/K+ - K+ - K1(1270), K1(1400) K*(892) K0*(1430), K2*(1430) ρ(770)

  13.  in J/K+ - K+ -  K*0(1430) K*

  14.  in

  15. f0(980) in J/+-,K+K- BESII preliminary • Important parameters from PWA fit: • Large coupling with KK indicates big component in f0(980) f0(980) f0(1370) f2(1525) f0(980)

  16. f0(1370) in J/+-, +- BESII preliminary • There has been some debate whether f0(1370) exists or not. • f0(1370) clearly seen in J/  , but not seen in J/  . f0(980) f0(1370) f2(1270) PWA 0++ components NO f0(1370)

  17. f0(1500) in J/+-, 00 BESII preliminary f2(1270) f0(1500) f0(1710) f0(1500) f2(1270) • One scalar with a mass = 1466  6  16 MeV is needed in J/  . • It’s also needed in the fit of J/  , kk • No peak directly seen in , KK, , KK channels. f0(1500)

  18. f0(1710) in PWA analysis shows one scalar. f2(1525) f0(1710) f2(1525) f0(1710) Phys. Rev. D 68 (2003) 052003

  19. f0(1710) in J/ f2(1270) • The scalar around 1710MeV with mass • Combine the branching ration of  and kk, we obtain: f0(1710) f2(1270) f0(1710) BESII preliminary

  20. f0(1710) in J/K+K-, +- • Clear f0(1710) peak in J/  KK. • No f0(1710) observed in J/   ! f0(1710) f2(1270) NO f0(1710) PWA 0++ components hep-ex/0409007

  21. f0(1790) in J/K+K-, +- BESII preliminary • A clear peak around 1790 MeV is observed in J/  +-. • No evident peak in J/  KK. If f0(1790) were the same as f0(1710), we would have: Inconsistent with what we observed in J/    , KK! f0(1790) f0(1710) ?

  22. Summary Summary of Scalar Meson at BES  Clear seen(peak + fit)  in the fit

  23. Summary • The existence of  is confirmed in J/+ - with pole position: • Evidence for the  as a peak close to threshold. Pole position:

  24. Summary • f0(980) is clearly seen in both +-, K+ K- data, parameters of f0(980)are well determined.

  25. Summary • f0(1370) is clearly seen in J/+- , But not evidence in J/+ - • f0(1500)is seen in J/ channel with mass: • f0(1710)is clearly seen in J/ KK with mass and width:

  26. Summary • f0(1710)is also seen in the J/, and K+K, but not seen in J/ +- • f0(1790) is needed in the fit of J/ +-, and need more study.

  27. Thank you!

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