Charmonium Physics. Zhengguo Zhao. University of Science and Technology of China (USTC) PIC2010 Karlsruhe, Zhengguo Zhao

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1 Charmonium Physics Zhengguo Zhao University of Science and Technology of China (USTC) PIC2010 Karlsruhe, Zhengguo Zhao 1

2 Outline Introduction to charm quark and charmonia Recent results - New resonances, a 0 (980)-f 0 (980) mixing - η c, h c, χ cj High mass ψ states and XYZ particles Summary PIC2010 Karlsruhe, Zhengguo Zhao 2

3 c quark was predicted by S. Glashow, J.Lliopoulos and L. Maiani in Discovered in Nobel prize for physics of 1976 Burten Richter s team with MarkI at SPEAR of SLAC Samuel Jing s team at AGS of BNL PIC2010 Karlsruhe, Zhengguo Zhao 3

4 Charm Quark and the Standard Model Heavy quark PIC2010 Karlsruhe, Zhengguo Zhao 4

5 Parity: P = (-1) L+1, C = (-1) L+S Total spin: S = 0, 1 Total angular momentum: J = S + L Quantum state: n 2S+1 L J Quantum number: J PC Much needs to be disentabgled above open charm Well understood below open charm PIC2010 Karlsruhe, Zhengguo Zhao 5

6 Quarkonium Potential Potential = Coulomb + Linear Heavy quarks can be treated as none relativistic approximation One gluon exchange dominant at small distance (asymptotic freedom): V~1/r Confining potential at large distance: Consider spin-spin efferct PIC2010 Karlsruhe, Zhengguo Zhao 6

7 Charmonium Production e + e - γ J PC =1 -- J PC =1 -- γ C C e + C C e - e + e - γ γ C C C=+1 e + e - annihilation Initial state radiation Two-photon production Double charmonium production pp annihilation All quantum number available PIC2010 Karlsruhe, Zhengguo Zhao Color suppressed b c decays 7

8 Charmonium Transition and Decays Quarkonium are unstable and decays through Annihilation - Generally suppressed for bound states - Clean experimental signal to decay to leptons Strong interaction - Dominant above D meson (3.77 GeV) - Suppressed below M D threshold Radiative transition - EM radiative transition emits γ - Emission of gluons produce light quarks Decays features Suppression of strong decays leads to narrow width, thus longer life time Radiative transitions are most accessible, and competitive PIC2010 Karlsruhe, Zhengguo Zhao 8

9 Data Sample For J/ψ and ψ(2s) J/ψ ψ(2s) MKIII CBAL BESI BESII CLEO BESIII Both CELO and BESIII have ~900 pb -1 data sample taken at ψ(3770) PIC2010 Karlsruhe, Zhengguo Zhao 9

10 pp Mass Threshold 58 M J/ψ Data Sample BESII: PRL 91 (2003) M = (stat) (syst) Γ < 30MeV /c 2 (90%C.L.) M pp -2m p (GeV) The observed anomalous enhancement near pp mass threshold stimulated theoretical discussions pp bound states FSI effect... PIC2010 Karlsruhe, Zhengguo Zhao 10

11 pp Threshold from BESIII ψ(2s) π + π - J/ψ, J/ψ γpp J/ψ γpp Chinese Physics C 34, 421 (2010) BESIII preliminary M = (stat) (syst) Γ < 38MeV /c 2 (90%C.L.) M= ± 0.8 MeV/c 2 Γ < 8 MeV (90%C.L.) Statistical error only! PIC2010 Karlsruhe, Zhengguo Zhao 11

12 Confirmation from CLEO QWG2010 Z. Metreveli 26 M ψ(2s) data sample ψ(2s) π + π - J/ψ, J/ψ γpp Fit with one resonance as BES did M = MeV Γ = MeV B 1 (J /ψ γr) B 2 (R pp ) = Fit with three contributions M = (stat) +9 7 (syst)mev Γ = MeV(26.1%C.L.) B 1 (J /ψ γr) B 2 (R pp ) = [ (stat) (syst)] 10 5 PIC2010 Karlsruhe, Zhengguo Zhao 12

13 pp Threshold from ψ(2s) γpp CLEO BESII CLEO N(event) 11.7± B(ψ(2S) γr) B(R pp) (90% C.L.) < < No threshold enhancement are observed Pure FSI is disfavored PIC2010 Karlsruhe, Zhengguo Zhao 13

14 Observation of X(1835) from J/ψ γπ + π - η BESII: PRL95,262001(2005) M=1833.7±6.1(stat)±2.7(syst)MeV Γ=67.7±20.3(stst)±7.7(syst)MeV X(1835) is confirmed at BESIII Two new resonances are observed PWA is needed, inference among the resonances needs to be considered η ->γρ, π + π - η Total bkg BESIII preliminary State M(MeV) Γ(MeV) Stat. sig. (σ) X(1835) ± ± X(2120) ± ± X(2370) ± ± PIC2010 Karlsruhe, Zhengguo Zhao 14

15 Observation of X(1870) BESIII preliminary f 1 (1285) X(1870) η(1405) Significance: 7.7 σ J/ψ ωx, X π + π - η X a + 0 π + M=1873 ± 11 MeV Γ=82 ± 19 MeV Statistical error only! Is X(1870) a new resonance, or η 2 (1870) or X(1835)? PIC2010 Karlsruhe, Zhengguo Zhao 15

16 Study of a 0 (980) f 0 (980) mixing Mixing intensity provides important information in understanding the nature of a 0 (980) and f 0 (980). Narrow peak (8 MeV) at around 980 MeV can be expected in ηπ (J/ψ φf 0 φa 0 φηπ case) or π + π - (χ c1 a 0 π 0 f 0 π 0 π + π - π 0 case) invariant mass spectra. J/ψ φf 0 φa 0 φηπ χ c1 a 0 π 0 f 0 π 0 π + π - π 0 PIC2010 Karlsruhe, Zhengguo Zhao 16

17 PIC2010 Karlsruhe, Zhengguo Zhao 17

18 PIC2010 Karlsruhe, Zhengguo Zhao 18

19 e + e - e + e - η c η c K s K + π - Babar: PRD (2010) V. Druzhinin ICHEP2010 M(MeV) Γ(MeV) PDG 2980 ± ±2.9 Babar 2982±0.4± ±1.2±0.8 CLEO 0.407±0.022±0.028 Babar 0.379±0.009±0.031 PDG 0.44±0.04 PIC2010 Karlsruhe, Zhengguo Zhao 19

20 Cross Section and Form Factor e + e - e + e - η c Babar: QWG 2010, Christ West Cross section of e + e - e + e - η c Form factor e + e - e + e - η c LO pqcd PLB413, 410(1997) Systematically lower than LO pqcd Λ = 8.5 ± 0.6 ± 0.7 GeV 2 consistent with theoretical predictions Λ = 8.4 ± 0.4GeV 2 (Lattice QCD) Λ = m 2 (J/ψ) = 9.6 ±0.6 GeV 2 (Vector meson dominant) PIC2010 Karlsruhe, Zhengguo Zhao 20

21 γ * γ * η c (2S), η c (2S) K s K + π - /K + K - π + π - π 0 Babar: V. Druzhinin ICHEP2010 N(η c (2S)) =620±70± fb -1 M (MeV) Γ (MeV) PDG 3630±3.4± ±8.3±2.5 Babar ±1.5± ±4.4±2.5 First measurement N(η c (2S)) =1190±130±180 PIC2010 Karlsruhe, Zhengguo Zhao 21

22 First Observation of η c (2S) 6 prongs 923 fb -1 Belle: H. Nakazawa, ICHEP2010 PIC2010 Karlsruhe, Zhengguo Zhao 22

23 Search for ψ(2s) γη c (2S) η c (2S) observed in B decays, γγ fusion and e + e - J/ψX Only K s Kπ decay mode observed M = 3673±4 MeV/c 2 Γ = 14±7 MeV/c 2 For ψ(2s) γη c (2S) search - Allow M1 transition - Predicted B: ( ) search with exclusive decay modes PIC2010 Karlsruhe, Zhengguo Zhao 23

24 ψ(2s) γη c (2S) CELO: QWG2010, Ryan Mitchell Sum of the seven channels No significant signals are observed PIC2010 Karlsruhe, Zhengguo Zhao 24

25 CLEO Search for η c (2S) with η,η No signal is seen PIC2010 Karlsruhe, Zhengguo Zhao 25

26 Search for η c (2S) π + π - η c (1S) CELO: QWG2010 Ryan Mitchell Decay channel ψ(2s) γη c (2S) η c (2S) π + π - η c (1S) η c (1S) K s Kπ/KKπ 0 /4π/2K2π Select mass of η c (1S) Look at energy of γ Branching fraction = ( ± 0.18) 10 4 < (90%C.L.) PIC2010 Karlsruhe, Zhengguo Zhao 26

27 ψ(2s) Xpp, X=η,π 0 CLEO Factor of two improvement PIC2010 Karlsruhe, Zhengguo Zhao 27

28 Potential model with spin-spin interaction gives none zero ΔM hf (1P) = m(h c ) 1 9 [m(χ c 0) + 3m(χ c1 ) + 5m(χ c 2 )] h c ( 1 P 1 ) State E835 has the first evidence from pp h c γη c CLEO observed from ψ(2s) π 0 h c, h c γη c and reported ΔM hf =0.08±0.18±0.12 MeV/c 2 PIC2010 Karlsruhe, Zhengguo Zhao 28

29 h c at CLEO PIC2010 Karlsruhe, Zhengguo Zhao 29

30 h c State at BESIII ψ(2s) π 0 h c, h c γη c, E1 taged ψ(2s) π 0 h c M(h c )= ±0.13±0.18MeV Γ(h c ) = 0.73±0.45±0.28MeV <1.44MeV@90%CL (1 st measurement) B(ψ(2S) π 0 h c ) Br(h c γη c ) = (4.58 ± 0.40 ± 0.50) 10-4 First measurement B(ψ π 0 h c )=(8.4±1.3±1.0) 10-4 B(h c γη c )= (54.3±6.7±5.2)% BESIII: PRL104, (2010) PIC2010 Karlsruhe, Zhengguo Zhao 30

31 χ cj (1 3 P J ) States Study of the χ cj decays provide information to Understand gluonium, e.g. χ c gg (qq)(qq) C. Amsler and F. E. Close, Phys. Rev. D 53, 295 (1996). Test of Color Octet Mechanism G. T. Bodwin et al., Phys Rev. Lett. D51, 1125 (1995). H.-W. Huang and K.-T. Chao, Phys.Rev.D54, 6850(1996). J. Bolz et al., Eur. Phys. J. C 2, 705 (1998). PIC2010 Karlsruhe, Zhengguo Zhao 31

32 Radiative Decays of χ cj Preliminary results from 712 fb -1 ϒ(4S) data First evidence of B + K + χ c2 (χ c2 γj/ψ) PIC2010 Karlsruhe, Zhengguo Zhao 32

33 ψ(2s) γχ cj ; χ cj π 0 π 0, ηη; π 0 /η γγ χ c1 π 0 π 0, ηη not allowed by parity conservation. ψ(2s) γπ 0 π 0 χ c0 ψ(2s) γηη χ c0 χ c2 χ c2 BESIII: PRD 81, (2010). CLEO: PRD 79, (2009). Decay mode χ c0 (10-3 ) χ c2 (10-3 ) π 0 π 0 PDG ± ±0.08 BESIII 3.23±0.03±0.23± ±0.02±0.06±0.04 ηη CLEOc 2.94±0.07±0.32± ±0.03±0.07±0.04 BESIII 3.44±0.10±0.24± ±0.04±0.05±0.03 PDG08 2.4±0.4 < 0.5 CLEOc 3.18±0.13±0.31± ±0.05±0.05±0.03 PIC2010 Karlsruhe, Zhengguo Zhao 33

34 BESIII preliminary First observation χ cj γv (V=φ, ω, ρ) B (10-6 ) BESIII CLEOc PRL101, (2008) pqcd hep-ph/ χ c0 γφ <14.8 < χ c1 γφ 27.3±5.5 stat < χ c2 γφ <7.8 < χ c0 γρ 0 <9.5 < χ c1 γρ 0 241±14 stat 243±19±22 14 χ c2 γρ 0 <19.7 < χ c0 γω <11.7 < χ c1 γω 73.5±7.6 stat 83±15± χ c2 γω <5.8 < pqcd predictions<<exp. data. May be explained by non-perturbative QCD loop corrections. D.Y. Chen et al, arxiv: v2. PIC2010 Karlsruhe, Zhengguo Zhao 34

35 χ cj VV, (V/V = ω, φ) BESII results: PLB 630, 7 (2005); PLB 642, 197 (2006) Didn t observe χ c1 φφ / ωω (highly suppressed because C-parity requires L = 2. B(10-3 ) χ c0 χ c2 φφ 0.94±0.21± ±0.30±0.25 ωω 2.29±0.58± ±0.47±0.36 BESIII: First observation χ cj φφ 4K signals χ c1 χ c0 χ c2 B(10-3 ) BESIII PDG08 χ c0 φφ 0.80± ±0.20 χ c1 φφ 0.42± χ c2 φφ 1.15± ±0.30 Errors: statistical only. PIC2010 Karlsruhe, Zhengguo Zhao

36 χ cj ωω / ωφ χ cj ωω 2(π + π - π 0 ) ωω χ cj ωφ (π + π - π 0 )(KK) ωφ First observation of χ c1 ωω First observation of Doubly OZI suppressed χ cj ωφ PIC2010 Karlsruhe, Zhengguo Zhao 36

37 χ cj Xpp, X=π 0, η, ω Reaction studied by CLEO PIC2010 Karlsruhe, Zhengguo Zhao 37

38 CLEO Factor of three smaller Branching Fraction of χ cj Xpp First measurement Meson emission model predicts [T.Barnes et al., PRD (2010): B(χ c0 π 0 pp)= , B(χ c1 π 0 pp)= A factor of 3 and 10 below the CLEO measurements meson emission is not the dominant decay mechanism. PIC2010 Karlsruhe, Zhengguo Zhao 38

39 First observation of ψ(2s) γγj/ψ Two photon transitions are well known in excitations of molecules, atomic hydrogen, and positronium. A. Quattropani etal, PRA 25, 3079 (1982). F. Bassani etal, PRL 39, 1070 (1977). A. Quattropani etal, PRL 50, 1258 (1983). CLEO observed two photon transitions in Υ(3S) Υ(2S). F. Butler etal, PRD 49, 40 (1994). Never been observed in the charmonium system. Theoretically: Potential models give discrete spectra for ψ(2s) γχ cj, χ cj γj/ ψ Coupled channel models can give continuous spectra. Theoretical work is ongoing. 39 PIC2010 Karlsruhe, Zhengguo Zhao

40 PIC2010 Karlsruhe, Zhengguo Zhao 40

41 R R = σ(e + e - hadron)/σ(e + e - µ + µ - ) Above the open charm, the region has not yet carefully studies with direct e + e - data. Mass region where most of the XYZ particles are found. Any possible new state that has not yet discovered? Do we fully understand the high mass ψ states? PIC2010 Karlsruhe, Zhengguo Zhao 41

42 R Values and Y States R(s) = σ(e + e hadrons)/σ(e + e µ + µ ) R uds Opportunity for BESIII Detailed scan (a few MeV steps, 10K each energy point) High statistics data taken at each peak ( ) for exclusive channel study PIC2010 Karlsruhe, Zhengguo Zhao 42

43 Summary (I) X(1860) from J/ψ γpp confirmed by CLEO and BESIII, not seen in the ψ(2s) γpp. X(1835) is confirmed by BESIII, Two new resonances at 2125 MeV, 2370 MeV are reported from J/ψ γπ + π - η decays (BESIII). No η c (2S) signal is found from ψ(2s) γη c (2S) (CLEO) Clear signal of η c (2S) K s K + π - /K + K - π + π - π 0 ; First measurement of the ratio of their branching fraction (Babar). First observation of η c (2S) 6 prongs (Belle). h c ( 1 P 1 ) found from ψ(2s) π 0 h c (CELO, BESIII). First measurements of Γ(h c ), Br(ψ π 0 h c ) and Br(h c γη c ) (BESIII). PIC2010 Karlsruhe, Zhengguo Zhao 43

44 Summary (II) First evidence of B + K + χ c2 (χ c2 γj/ψ) (Belle). First observation of χ c1 φφ, χ c1 ωω, χ cj ωφ (BESIII). First measurement of χ cj ωpp (CLEO). First observation of ψ(2s) γγj/ψ (BESIII). Study of the exclusive decay channels of high mass ψ resonances may greatly help our understanding of these broad resonances and the X,Y,Z particles as well. PIC2010 Karlsruhe, Zhengguo Zhao 44

45 PIC2010 Karlsruhe, Zhengguo Zhao 45

46 Higher Multipoles in ψ(2s) γχ cj, χ cj γj/ψ PIC2010 Karlsruhe, Zhengguo Zhao 46

47 Measure Multipoles with Angular Distribution PIC2010 Karlsruhe, Zhengguo Zhao 47

48 Magnetic Quadrupole Amplitude CLEO s results have the best precision and are consistent with theoretical expectation PIC2010 Karlsruhe, Zhengguo Zhao 48

49 CLEO: E3 Term and the κ c Anomalous magenetic moment of the charm quark is consistent with zero PIC2010 Karlsruhe, Zhengguo Zhao 49

50 The h c (1 1 P 1 ) Quantum numbers: J PC = 1 +- Expected to have small width: Γ < 1 MeV Hard to access. Can be produced in: pp annihilation (unknown BR) radiative E1 decay from η c ' One of the main decay modes should be h c η c γ Precision measurements of the h c parameters give unique possibility to test the hyperfine splitting potential. The h c is expected to be within a few MeV from the center of gravity of the χ cj states: PIC2010 Karlsruhe, Zhengguo Zhao 50

51 Resonances in the open charm region BESII Phys.Lett.B660,315(2008) R res =R BW +R int Resonance shapes PIC2010 Karlsruhe, Zhengguo Zhao 51

52 Parameters of the broad resonances Parameters (M, Γ tot, Γ ee ) of the J PC = 1 conventional Charmonia ψ(3770), ψ(4040), ψ(4160), ψ(4415) remain quite uncertain and model dependent M, MeV Γ tot, MeV Γ ee, kev δ, deg ψ(3770) ± ± ± PDG ± ± ± BES08 ψ(4040) 4039 ± 1 80 ± ± 0.07 PDG ± ± ± ± 46 BES08 ψ(4160) 4153 ± ± ± 0.07 PDG ± ± ± ± 57 BES08 ψ(4415) 4421 ± 4 62 ± ± 0.07 PDG ± ± ± ± 88 BES08 PIC2010 Karlsruhe, Zhengguo Zhao 52

53 χ cj ppπ + π - π 0 Results of 2-D fit Nonback AGUST fnc PIC2010 Karlsruhe, Zhengguo Zhao 53

54 χ cj ppγγ (π 0 /η γγ) Perform 1-D unbinned extended maximum likelihood fit in M(ppX) PIC2010 Karlsruhe, Zhengguo Zhao 54