Charmonium Spectroscopy and Decay at CLEO c

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1 Charmonium Spectroscopy and Decay at CLEO c Helmut Vogel Carnegie Mellon University CLEO c at CESR (for the CLEO Collaboration) PHIPSI09, IHEP, Beijing, 13 Oct 2009

2 Acknowledgments and thanks to: Matt Shepherd Brian Heltsley Jon Rosner CLEOAC and other CLEOns

3 CLEO c Data Sample for Charmonium Program 818/pb at (3770) (mostly open charm see talks by Peter Zweber (today) and RoyBriere (Friday)), and J/ 54/pb at (2S) > 27 M (2S) (largest pre BESIII world supply) In praise of (2S): B( (2S) cj) 9% for each of J=0,1,2 B( (2S) + J/ ) = 35% ( 75%) Clean, tagged, abundant cj, J/ (and hc)! Study Decays of states (hadronic & radiative) Transitions between states Spectrum of states Overarching theme: Use charmonium as a laboratory to test quarkonium potential models QCD, pqcd, NRQCD, LQCD 3

4 Two Body Mesonic Decays of χcj χc0 χc2 χc0 χc2 Two body decays are theoretically clean : probe role of the color octet mechanism probe gluon content of final state mesons Results for two body baryonic decays have also recently been published: CLEO PRD 78, (R) (2008) BF or 90% CL UL (10 3) probes D OZI/S OZI amplitudes (see next slide) CLEO PRD 79, (2009) Substantial improvement over current world averages in some channels! 4

5 Example: χcj η η ( ) ( ) Measured BRs constrain ratio of Double OZI to Single OZI amplitudes Theory: Close & Zhao, PRD 71, , factorization a la Zhao, PRD 72, ; PLB 659, 221 χc0 PP χc2 PP η'η' ηη ηη' ηη η'η' ηη' Data suggest small (if any) contribution of DOZI decays in 0 + channel. 5

6 Evidence for Hadronic Decay of the hc The only previously observed decay: ψ(2s) π0hc) x B(hc γηc) ; product BF: (4.2 ± 0.6) x 10 4 (CLEO PRL 101, (2008)) (Our recent precision mass measurement finds HF splitting <1MeV for 1P states) CLEO PRD 80, (R) (2009) > 4σ significance Godfrey & Rosner predict 56.8% direct hadronic decay (PRD 66, (2002)) Expect odd number of pions (negative G parity) Measure B(ψ(2S) π0hc) x B(hc X) X = n(π+π ) π0 (n=1,2,3): Mode Product BF (10 5) π+π π0 < ± 0.5 ± 0.4 < 2.4 2(π+π ) π0 3(π+π ) π0 2(π+π-)π0 Invariant Mass (GeV/c2) 6

7 Radiative Decays and Transitions 7

8 B(ψ(2S) γgg) / B(ψ(2S) ggg) CLEO Preliminary State J/ψ ψ(2s) ϒ(1S) ϒ(2S) ϒ(3S) B(X γgg) / B(X ggg) ± ± ± ± ± ± ± ± ± ± CLEO PRD 78, (2008) CLEO PRD 80, (2009) CLEO PRD 74, (2006) 8

9 J/ψ,ψ(2S) γ ηc X CLEO PRL 102, (2009) 9

10 The ηc Lineshape 10

11 Eγ = 48 MeV inclusive analysis too difficult; instead search for ψ(2s) γηc ; ηc X ψ(2s) γηc ; ηc π+π ηc; ηc X Calibrate analysis on ψ(2s) γχc2 Using known B(ηc KKπ) and ηc branching fractions, can set 90% C.L. limits ψ(2s) γηc? ηc KKπ ηc π+π-ηc Scaling from J/ψ γηc one expects B(ψ(2S) γηc ) = 4 x 10 4 Results (CLEO arxiv: ; subm. to PRD): B(ψ(2S) γηc ) < 7.4x10 4 B(ψ(2S) γηc ) x B(ηc π+π ηc) < 1.4x

12 J/ψ,ψ(2S) γ(π0,η,η ) J/ψ ψ(2s) γη mode (dominating QED bgd in γγ mode) γγ 3π0 π+π-π0 γπ+π- Results: consistent with known η η' mixing surprise: R1, R2 expected to be about equal! CLEO PRD 79, (R) (2009) 12

13 χcj γ(ρ,ω,φ) Look for: M(π+π ) ψ(2s) γ(low)χcj χcj γ(high)(ρ,ω,φ) γρ M(π+π π0) Significant signals observed in: χc1 γρ χc1 γω 1. cut on hadronic mass 2. look at low E photon γω γφ CLEO PRL 101, (2008) Expect process to be analogous to that of glueball production, e.g., in J/ψ γfj pqcd predicts rates an order of magnitude lower than observed! (Gao, Zhang, Chao, Chin.Phys.Lett. 23, 2376 (2006) [arxiv:hep-ph/ ]) 13

14 χcj γγ Two photon widths of χcj probe relativistic and radiative corrections known to be significant in charmonium. ψ(2s) γχcj; χcj γγ Results: Γγγ(χc2) = 0.66 ± 0.07stat ± 0.04syst ± 0.05PDG kev Γγγ(χc0) = 2.36 ± 0.35stat ± 0.11syst ± 0.19PDG kev Ratio = ± 0.050stat ± 0.018syst ± 0.031PDG In pqcd, uncertainties due to quark mass and wave function cancel, making the ratio of widths, R, a key quantity. To first order in αs: New world avg.: R = 0.22 ± 0.03 higher order corrections very significant CLEO PRD 78, (2008) 14

15 J/ 3 This is the quarkonium analogue of ortho positronium decay. No 3γ decay of a meson has been observed before. MC MC Tag via (2S) + J/ (eliminates QED background!) Veto resonances,, ', c 0 Main remaining background: J/ 0 0 MC Data 15

16 J/ 3 Perform kinematic fit; Signal peaks at low 2/dof Background rises away from zero (and is independent of 0 0 substructure!) Result (CLEO PRL 101, (2008)): B = (1.2 ± 0.3 ± 0.2) x 10 5 (6 ) First observed 3 decay of any meson! region used to normalize bkgd signal Theory: in QED, B(3 )/B(3g) ( / s)3 and B(3 ) ( /14)B 3 x10 5 But NLO QCD corrections give negative rate! (Higher order corrections very significant) background subtracted As byproduct we obtain upper limit on ηc γγ : B(ηc γγ) < (90% CL), PDG: (2.7±0.9)

17 Higher Multipoles in Radiative Transitions hot off the press! (arxiv: (2009) Long standing discrepancy between theory and several previous experiments! 17

18 Higher Multipoles, cont'd. 18

19 Higher Multipoles, cont'd. 19

20 Higher Multipoles, cont'd. Project theory E1+M2 J=1 pure E1 theory E1+M2 J=2 pure E1 Data shows significant M2 admixture: >11σ for J=1, > 6σ for J=2! 20

21 Higher Multipoles, concluded. Good fit (multi parameter, log likelihood) obtained assuming mc = 1.5 GeV no electric octupole (E3) contribution no anomalous quark magnetic moment Measured M2 amplitudes agree with theoretical predictions e.g., Karl et al., PRL 45, 215 (1980), Sebastian et al., PRD 45, 3163 (1992) Resolves a long standing discrepancy between theory and experiment. CLEO arxiv: (2009); submitted to PRD 21

22 Summary of CLEO c Charmonium Results Precision measurement of hadronic two body decays of χcj First evidence for hadronic hc decay (and precision measurement of the hc mass) First measurement of B(ψ(2S) γgg)/b(ψ(2s) ggg) ; completes the set for heavy vector states New measurements for M1 transitions J/ψ,ψ(2S) γηc Understanding of lineshape crucial for ηc mass and BF measurements Study of J/ψ,ψ(2S) γ(π0,η,η ); surprising suppression of ψ(2s) γη First observation of χcj γ(ρ,ω); rates much larger than predicted Precision measurement of two photon widths of χc(0,2) First observation of the 3 photon decay of a meson: J/ 3 Precision measurement of higher multipoles (M2) in radiative transitions 22

23 Concluding Remarks Rich program of hadronic physics at CLEO c (too extensive to cover it all here) precision measurements of the mass of η (PRL 99, (2007)) and η (PRL 101, (2008)) most precise single measurement of all dominant η B.F. s (PRL 99, (2008)), η B.F. s (arxiv: ), and rare η decays (PRL 102, (2008)) precision branching fractions for ψ X J/ψ (PRD 78, (R) (2008))...and several analyses still in the pipeline ψ ππ J/ψ matrix elements χcj Xpp (J/ψ, ψ ) (γ,π0)pp; search for invisible (radiative) decays of J/ψ spectroscopy in hadronic χcj decay CLEO c has laid a solid foundation for BESIII to build on. 23

24 Backup Slides 24

25 (Aside: Precision hc Mass Measurement) CLEO PRL 101, (2008) 9 Result: M(hc)=( ±0.19±0.12) MeV cf. <M( cj)> =( ±0.11) MeV (PDG) HF splitting of 1P states is negligibly small! 25

26 26

27 Data MC η' Mass Use (2S) + J/, J/ ' Similar technique as in mass measurement Result: (CLEO arxiv: , subm' to PRL) M( ')=( ±0.054±0.036) MeV consistent with and substantially more precise than previous world average Implication for the pseudoscalar ' mixing angle: P=(41.461±0.008)0 (Jones & Scadron 1979) Agrees with P from BFs: flavor symm' breaking small? check: J/ M M(PDG07) in MeV 27

28 η branching fractions 28

29 structure in the decay χc1(1p) γ(ρ,ω) The ρ decay exhibits Polarization longitudinal polarization Statistics are less precise for ω, but it is also consistent with longitudinal polarization This parallels that measured for a1 γρ by VES (Z. Phys. C 66, 71 (1995)) Expected from Landau-Yang ρ decay angle (top) orientation of ω decay plane (bottom) 29 M. R. Shepherd GHP Workshop, Denver April 29, 2009