Charmonium Decays at BESIII Haixuan CHEN IHEP Beijing
Charmonium Decays at BESIII Haixuan CHEN IHEP, Beijing 2007. 11. 26
Many results on Charmonium decays have been produced at BESII • Charmonium Family below D-Dbar threshold • There were many topics on Charmonium physics at BESIII • Only a few topics are discussed in this talk
Charmonium Decays at BESIII BEPCII Status • Lpeak~3 x 1032 cm-2 s-1 at Ecm=3. 7 Ge. V • average luminosity: Lavg=0. 5 Lpeak • energy spread: ~1. 5 Me. V at Ecm=3. 7 Ge. V
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 – running time: ~50, 000 s/day (1 day=86, 400 s) – ’ 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. most interesting! • Precise measurement of the mass of the spinsinglet charmonium ηc can provide information on the hyperfine splittings of spin-singlet and spin-triplet charmononium.
M( )- M( ) (potential models) M( )- M( ) (Lattice QCD) S. Choe et al, QCD-TARO hep-lat 0307004 116. 5 Me. V PDG: Not in agreement! Comes from all the measurement of
M(hc) current status Status of Gtot(hc) is even worse! J/Ψ γηc measurements are consistently lower than others
Measurement of 394± 52 at BESII 545± 73 86± 15 436± 49 Kinematic Fit σ(4 prongs) ≈13 198± 31 Me. V/c 2
Measurement of at BESIII using sample BESIII simulation Preliminary If Ntot( ) = 200 M (4 days) We will have: Nobs( )= Supposing
Measurement of using at BESIII sample BESIII simulation Preliminary If Ntot( ) = 820 M (164 days) We will have: Nobs( Supposing )=
Also very interesting! decays 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 BESIII simulation Very preliminary Supposing 600 M (120 days) • More decay modes • Branching fraction • Intermediate states
decays • Lots of unknown c. J 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 (QWG 07)
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(2 S) 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. Kabir K. and C. N. Yang, Phys. Rev. 106, 1367 (1957) In spin-1/2 Hyperonsnonleptonic decays, the angular distribution of the daughter baryon: where is thehyperon 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. D 76, 036005 (2007)
H. Chen, R. G. Ping, Phys. Rev. D 76, 036005 (2007)
H. Chen, R. G. Ping, Phys. Rev. D 76, 036005 (2007)
Experimental Prospects ■ Experimental Method:
■Measurement sensitivity H. Chen, R. G. Ping, Phys. Rev. D 76, 036005 (2007)
■ Evaluation of sensitivity Assume the J/ψ sample: 1010 (400 days) Assume BESII detection efficiency Channel J/ψ→ efficiency Parameters α ~20% √ ~6% ~1. 4% √ Systematic error is dominant ! Sensitivity δ(α) Measured BESIII 20% 3× 10 -3 20% 2% ---- 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 Λ → pπ AΛ 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 AΞ CKM ≈-4× 10 -6 Weigberg ≈-3. 2× 10 -4 Left-right(isoconjugate) ≈ 2. 5× 10 -5 Left-right(with mixing) ≤ 1× 10 -5
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