Charmonium Decays at BESIII Haixuan CHEN IHEP,Beijing 2007.11.26 TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAAAAAAA

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

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

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: 58  106 now ’ production cross section: 640 nb BESIII running at ’ peak average ’ events rate: 100 Hz ’ events/day = 5  106 BESII: 14  106 now; CLEOc: 29  106 now

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

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!

M( )- M( ) (potential models) M( )- M( ) (Lattice QCD) S.Choe et al, QCD-TARO hep-lat0307004 116.5 MeV PDG: Comes from all the measurement of Not in agreement!

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

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

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

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

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!

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

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.

Many results from CLEOc (QWG07)

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

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:

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

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

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

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

Experimental Prospects ■Experimental Method:

■Measurement sensitivity H. Chen, R. G. Ping, Phys. Rev. D76, 036005 (2007)

√ 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%

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.

Thank you!

Backup Slide

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