1. Charmonium Decays at BESIII
Haixuan CHEN
IHEP,Beijing
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2. There were many topics on Charmonium physics at BESIII
Many results on Charmonium decays have been produced at BESII
There were many topics on Charmonium physics at BESIII
Only a few topics are discussed in this talk
Charmonium
Family below
D-Dbar
threshold

3. Charmonium Decays at BESIII
BEPCII Status
Lpeak~3x1032cm-2s-1 at Ecm=3.7 GeV
average luminosity: Lavg=0.5 Lpeak
energy spread: ~1.5 MeV at Ecm=3.7 GeV

4. Charmonia production at BESIII
J/ production cross section: 3400 nb
BESIII running at J/ peak
average J/ events rate: 100 Hz
running time: ~50,000 s/day (1 day=86,400 s)
J/ events/day = 25  106
BESII:  106 now
’ production cross section: 640 nb
BESIII running at ’ peak
average ’ events rate: 100 Hz
’ events/day = 5  106
BESII:  106 now; CLEOc: 29  106 now

5. Topics that are focused on:
decays (Mass and Width)
decays
baryonic decays (hyperon decay parameters)

6. Mass and Width of
Results on and mass and width of the are not as good as for the
Precise measurement of the mass of the spin-singlet charmonium ηc can provide information on the hyperfine splittings of spin-singlet and spin-triplet charmononium.
most interesting!

7. M( )- M( ) (potential models)
M( )- M( ) (Lattice QCD)
S.Choe et al, QCD-TARO hep-lat
116.5
MeV
PDG:
Comes from all the measurement of
Not in agreement!

8. Status of Gtot(hc) is even worse!
M(hc) current status
J/Ψ γηc measurements are
consistently lower than others

9. Measurement of at BESII
394±52
545±73
Kinematic Fit
σ(4prongs) ≈13 MeV/c2
86±15
436±49
198±31

10. Measurement of at BESIII using sample
BESIII simulation
Preliminary
If Ntot( ) = 200M (4days)
We will have:
Nobs( ) =
Supposing

11. Measurement of at BESIII using sample
BESIII simulation
Preliminary
If Ntot( ) = 820M (164days)
We will have:
Nobs( ) =
Supposing

12. decays Also very interesting!
W. -M. Yao et al. (PDG), J. Phys. G 33, 1(2006)
No results of B.R.( ) except an U.L.
CLEOc will have more results on using the new sample!

13. decays Branching fraction Intermediate states Supposing 600M (120days)
BESIII simulation
Very preliminary
Supposing 600M (120days)
More decay modes
Branching fraction
Intermediate states

14. decays Lots of unknown cJ decay modes are waiting to be discovered.
Help to understand the role of the color octet configuration
With decays , can be analyzed using sample.

15. Many results from CLEOc (QWG07)

16. BESIII can do more with large sample:
BESIII simulation
Very preliminary
BESIII can do more with large sample:
Precisely measure the mass, width and B.R.
Partial Wave Analysis for the intermediate states in multibody decays

17. Study of hyperon decay parameters
in J/ψ or ψ(2S) decays
■ Hyperon non-leptoinc decays play an important role for people to
understand Parity asymmetry in particle physics
T. D. Lee and C. N. Yang, Phys. Rev. 108,1645 (1957)
T. D. Lee , J. Steinberger, G. Feinberg, P. K. Kabir and C. N. Yang, Phys.
Rev. 106, 1367 (1957)
In spin-1/2 Hyperons nonleptonic decays, the angular distribution of the daughter baryon:
where is the hyperon asymmetry parameter. It characterizes CP-odd observables A as:

18. Consider Λpπ- :
Where is the helicity amplitude for Λpπ- , and is the helicity values for proton.

19. H. Chen, R. G. Ping, Phys. Rev. D76, 036005 (2007)

20. H. Chen, R. G. Ping, Phys. Rev. D76, 036005 (2007)

21. H. Chen, R. G. Ping, Phys. Rev. D76, 036005 (2007)

22. Experimental Prospects
■Experimental Method:

23. ■Measurement sensitivity
H. Chen, R. G. Ping,
Phys. Rev. D76, (2007)

24. √ Sensitivity δ(α) Measured BESIII ~20% 20% 3×10-3 ~6% 2% ~1.4%
■ Evaluation of sensitivity
Systematic error is dominant !
Assume the J/ψ sample: 1010 (400days)
Assume BESII detection efficiency
Channel
J/ψ→
efficiency
Parameters α
Sensitivity δ(α)
Measured
BESIII
~20% √
20%
3×10-3
~6% 2%
~1.4% 1%

25. Summary Some topics on charmonium decays at BESIII are discussed.
With the high luminosity of BEPCII, large and data samples will be collected.
Precise measurements of mass, width and branching fractions of , and
Partial Wave Analysis can be done to the intermediate states in these decays if data sample is large enough.
Precise measurement of hyperon decay parameters can also be done at BESIII.

26. Thank you!

27. Backup Slide

28. Some predictions of A for Λ → pπ and Ξ→ Λπ
CKM
≈+5×10-5
Weigberg
≈-2.5×10-5
Left-right(isoconjugate)
≈ -1.1×10-5
Left-right(with mixing)
≤6×10-4
Charged Ξ→ Λπ
A Ξ
CKM
≈-4×10-6
Weigberg
≈-3.2×10-4
Left-right(isoconjugate)
≈ 2.5×10-5
Left-right(with mixing)
≤1×10-5