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Status of Charmonium Spectroscopy

Status of Charmonium Spectroscopy. Matteo Negrini INFN Ferrara Panda collaboration meeting Dubna, July 3, 2007. Outline. Overview of charmonium production mechanisms Conventional charmonia states New states in the charmonium mass region. The charmonium spectrum. Hic Sunt Leones. 3.87

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Status of Charmonium Spectroscopy

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  1. Status of Charmonium Spectroscopy Matteo Negrini INFN Ferrara Panda collaboration meeting Dubna, July 3, 2007

  2. Outline • Overview of charmonium production mechanisms • Conventional charmonia states • New states in the charmonium mass region M. Negrini - Panda Meeting Dubna - July 3, 2007

  3. The charmonium spectrum Hic Sunt Leones 3.87 DD* threshold 3.73 DD threshold M. Negrini - Panda Meeting Dubna - July 3, 2007

  4. Charmonium production • e+e- machines (MARK I-II-III, TPC, Crystal Ball, DASP, PLUTO, LEP, CLEO, KEDR, OLYA, CLEO-c, BES, BaBar, Belle) • direct formation (JPC = 1-- states) • gg production • initial state radiation • B meson decay • double charmonium production • pp annihilation (R704, E760, E835, PANDA) • hadroproduction (CDF, D0, LHC) • electroproduction (HERA-B, H1, ZEUS) M. Negrini - Panda Meeting Dubna - July 3, 2007

  5. Direct formation in e+e- annihilation • Only states with the photon quantum number (JPC=1--) • Other states may be accessed through radiative decays i.e. e+e- y'  ccJg CBAL Photon spectra observed by Crystal Ball PRL 45,1150 (1980) M. Negrini - Panda Meeting Dubna - July 3, 2007

  6. Initial state radiation processes • At B-factories: formation of 1-- states with m<10.58 GeV is possible after radiation of a photon from the e± in the initial state that lower the s of the interaction • ISR cross section for production of final state f: x=2Eg/s s’=s(1-x) Probability of ISR photon emission: M. Negrini - Panda Meeting Dubna - July 3, 2007

  7. gg production • Interaction of gg at e+e- machines • Production of C=+ states • The state is usually identified by its hadronic decays • The cross section for this process scales with BR(ccgg) C=+ M. Negrini - Panda Meeting Dubna - July 3, 2007

  8. B meson decay • Color suppressed B decays to charmonium states • Branching ratios of the order of 10-4 but large samples available at the B factories • Large discovery potential for the B factories in charmonium physics (hc', X(3872)) M. Negrini - Panda Meeting Dubna - July 3, 2007

  9. p e- Breco D* e+ Bsignal K X Inclusive charmonia in B decay • Fully reconstruct Breco in hadronic modes • The X mass distribution can be obtained from the momentum distribution of K± • Huge background due to secondary K± tracks • Observation of X states independent from the decay mode • Absolute measurement of BR(BXK) low mass region high mass region PRL 96, 052002 (2006) M. Negrini - Panda Meeting Dubna - July 3, 2007

  10. Double charmonium production • Associated production of 2 charmonium states in e+e- interaction • Reconstruct a J/y and compute the recoiling invariant mass • Observation of C=+ states • Cross section one order of magnitude larger than NRQCD predictions C=+ hc hc cc0 PRL 89, 142001 (2002) M. Negrini - Panda Meeting Dubna - July 3, 2007

  11. Direct formation in pp annihilation • Coherent annihilaton of the 3 quarks with the 3 antiquarks into a cc pair • Direct formation of states with all quantum numbers • Perform precision spectroscopy measurements through direct scan of the resonances • Large hadronic background M. Negrini - Panda Meeting Dubna - July 3, 2007

  12. pp annihilation: experimental technique • Antiproton beam on H gas target • The total energy is precisely known from the beam parameters (the detector resolution is not crucial) • Gaussian beam energy distribution s~400 keV (y' width 300 keV) • Measured cross section obtained counting events in the final state f • Convolution between resonance cross section and beam energy distribution M. Negrini - Panda Meeting Dubna - July 3, 2007

  13. hep-ex/0703012 E835 Direct measurement of the y' width • pp scan of y' observing e+e-X final state • Energy determination: • The largest systematic uncertainty on the width comes from the determination of the h factor • 2 scans performed with different techniques: • constant B: the measured width has a negative correlation with h • constant orbit: the measured width has a positive correlation with h • Combining two scan of similar luminosity the dependence of the result from h can be reduced f = revolution frequency L = orbit length h = phase-slip factor (machine parameter) M. Negrini - Panda Meeting Dubna - July 3, 2007

  14. hep-ex/0703012 E835 Direct measurement of the y' width M. Negrini - Panda Meeting Dubna - July 3, 2007

  15. The hc (11S0) • The ground state of charmonium (JPC=0-+) • The mass difference M(J/y)-M(hc) is a key parameter for the potential model • Observed in: • M1 radiative decays of J/y and y' • pp annihilation • gg fusion • B decay • double charmonium production M. Negrini - Panda Meeting Dubna - July 3, 2007

  16. The hc mass and width PDG 2006 Large width M and G measured by several experiments but discrepancies still present G = 25.5±3.4 MeV M = 2980.4±1.2 MeV M. Negrini - Panda Meeting Dubna - July 3, 2007

  17. Some recent hc width measurements PRL 92,142001 (2004) CLEO: G(hc) = 24.8±3.4±3.5 MeV E835 PLB 566,45 (2003) PRL 92,142002 (2004) E835: G(hc) = 20.4+7.7-6.7±2.0 MeV Babar: G(hc) = 34.3±2.3±0.9 MeV M. Negrini - Panda Meeting Dubna - July 3, 2007

  18. The ccJ (13PJ) • Produced in y' decay • BR(y'cc0g) = 9.2±0.4% • BR(y'cc1g) = 8.7±0.4% • BR(y'cc2g) = 8.1±0.4% • cc0 and cc1 produced in B decay • cc0 observed in double charmonium production • cc0 and cc2 produced in gg fusion • All can be directly formed in pp annihilation M. Negrini - Panda Meeting Dubna - July 3, 2007

  19. E835 ccJ scan at pp machines • Precision measurements of ccJ masses and widths obtained through direct scan at pp machines • Count the number of J/ye+e- in the final state (background ~0) cc0 cc1 cc2 PLB 533, 237 (2002) cc2 cc1 NPB 717, 34 (2005) M. Negrini - Panda Meeting Dubna - July 3, 2007

  20. Study of neutral hadronic channels at E835 • Study of hadronic decay modes of charmonium in pp annihilations • Small signals in presence of a large background • Possible observation through study of the interference between resonant and non-resonant amplitudes M. Negrini - Panda Meeting Dubna - July 3, 2007

  21. PRL 91, 091801 (2003) E835 Interference measurement of cc0p0p0 Interfering (helicity 0) Non-Interfering (helicity 1) Resonant M. Negrini - Panda Meeting Dubna - July 3, 2007

  22. The hc' (21S0) Photon energy distribution • First hc' candidate observed by Crystal Ball in 1982 • Observation of 5582±1270 photons from y'hc'g decay • M = 3594±5 MeV • G < 8 MeV (95% CL) • Never confirmed by other experiments • DM(y'-hc')=92 MeV • PQCD prediction for the M(y')-M(hc') mass splitting: CBAL PRL 48, 70 (1982) M. Negrini - Panda Meeting Dubna - July 3, 2007

  23. The hc' (21S0) • Twenty years later (2002) observation of the hc' by Belle • M = 3654±6±8 MeV • G < 55 MeV (90% CL) • Observation of 56 events with 21±2 expected background from BKKsK-p+ decay • Studied also by other experiments (Babar and CLEO) and with different techniques (gg, double charmonium) PRL 89, 102001 (2002) M. Negrini - Panda Meeting Dubna - July 3, 2007

  24. Mass and width of the hc' (21S0) The mass and width are not precisely known Several measurement, all consistent but with large errors M. Negrini - Panda Meeting Dubna - July 3, 2007

  25. The hc (11P1) • Quantum numbers: JPC = 1+- • Expected to have small width: G < 1 MeV • Hard to access. Can be produced in: • pp annihilation (unknown BR) • radiative E1 decay from hc' • One of the main decay modes should be hc hcg • Precision measurements of the hc parameters give unique possibility to test the hyperfine splitting potential. The hc is expected to be within a few MeV from the center of gravity of the ccJ states: M. Negrini - Panda Meeting Dubna - July 3, 2007

  26. PRL 69, 2337 (1992) E835 The hc (11P1) PRD 72, 032001 (2005) Observation by E760 of pp hc  J/yp0 The decay is isospin violating Not confirmed by E835 with larger statistics (2 running periods) E760 E835-1997 E835-2000 E760: M = 3526.3±0.2±0.2 MeV Narrow (G < 1.1 MeV at 90% CL) M. Negrini - Panda Meeting Dubna - July 3, 2007

  27. PRD 72, 032001 (2005) E835 hc hcg - E835 Excess of hc hcg, hc  gg events observed by E835 M = 3525.8±0.2±0.2 MeV Narrow (G < 1 MeV) G(pp)BR(hcg) ~ 12.0±4.5 eV compatible with expectations M. Negrini - Panda Meeting Dubna - July 3, 2007

  28. PRL 95, 102003 (2005) hc hcg - CLEO The y' decay mode is isospin violating Exclusive analysis (hc hadrons) The hc is reconstructed in 7 decay modes (sum of BR ~ 10%) Inclusive analysis Invariant mass recoiling against a p0 (after background rejection for events consistent with a radiative decay to hc) MC data CLEO results: M. Negrini - Panda Meeting Dubna - July 3, 2007

  29. BES Charmonium states above the DD threshold Compilation of R measurements in the region 2-5 GeV and latest BES measurement in the region 3.7-4.6 GeV • Region above DD mass threshold (3.72 GeV) is poorly known • Interesting region, rich of new states • Excited vector states investigated at e+e- machines (latest results by BES) • Only y(3770) clearly observed • considered to be the 3D1 charmonium state y(3770) y(4040) y(4160) y(4415) PRL 88, 101802 (2002) M. Negrini - Panda Meeting Dubna - July 3, 2007

  30. The new states • New states in the charmonium mass region have been recently observed at the B factories • Their nature is still unknown • Several hypothesis: • Charmonium (1),(2),(3) • D-D(*) molecules (4),(5) • Diquark-antidiquark (cu-cu) state (6) • Threshold effects • ... and others! Need experimental result to test models: • Quantum numbers • Decay modes • Branching ratios • Angular distributions • Charged partners? A few references: (1) Barnes and Godfrey, PRD 69, 054008 (2004) (4) Swanson, PLB 588, 189 (2004) (2) Eichten, Lane and Quigg, PRD 69, 094019 (2004) (5) Tornqvist, PLB 590, 209 (2004) (3) Suzuki, PRD 72, 114013 (2005) (6) Maiani, et. al., PRD 71, 014028 (2005) M. Negrini - Panda Meeting Dubna - July 3, 2007

  31. X(3872) CDF PRL 93, 072201 (2004) BELLE PRL 92, 262001 (2003) Discovered by Belle B+ K+ X(3872) X(3872)J/yp+p- (compatible with J/yr0) MX=3871.9±0.5 MeV/c2 GX<2.3 MeV/c2 at 90%CL at D0D0* threshold JPC=1++ favored BABAR PRD 71, 071103 (2005) D0 PRL 93, 162002 (2004) • Confirmed by: • CDF • D0 • BaBar M. Negrini - Panda Meeting Dubna - July 3, 2007

  32. X(3872) - p+p- mass distribution hep-ex/0505038 The pp invariant mass distribution is consistent with J/yr0 decay (isospin I=1) PRL 96, 102002 (2006) M. Negrini - Panda Meeting Dubna - July 3, 2007

  33. X(3872) - angular distribution 0++ and 0-+ ruled out by Belle 1++ and 2-+ favored by CDF c2/dof = 34/9 c2/dof = 34/9 JPC = 0++, 1++, 2-+, 1-- PRL 96, 102002 (2006) hep-ex/0505038 M. Negrini - Panda Meeting Dubna - July 3, 2007

  34. p e- Breco D* e+ Bsignal K X Inclusive charmonia in B decay high mass region • No X(3872) signal observed • BR(B±X(3872)K±)<3.2·10-4 at 90% CL • From BaBar-Belle average: • BR(B±X(3872)K±, X(3872)J/yp+p-)= • =(13.3±2.5)·10-6 • BR(X(3872)J/yp+p-)>4.2% at 90% CL PRL 96, 052002 (2006) M. Negrini - Panda Meeting Dubna - July 3, 2007

  35. X(3872)  J/yg hep-ex/0505037 PRD 74, 071101 (2006) Belle and BaBar see J/yg decay of X(3872) in B decays (B  J/yg K) N=13.6±4.4 • Implications: • C=+ for the X(3872) • I=1 for the (pp) in J/yp+p- • forbidden J/yp0p0, J/yp0, and J/yh decays • If X(3872) has I=0 the J/yp+p- decay must occur with isospin violation M. Negrini - Panda Meeting Dubna - July 3, 2007

  36. X(3872)  J/yw hep-ex/0505037 Observation of J/yw decay by Belle in B decays (B  J/yw K, w  p+p-p0) Branching ratio comparable to J/ypp: Hint for strong isospin violation effect in X(3872) decays: suggestions of X(3872) as I=0 and I=1 mixture M. Negrini - Panda Meeting Dubna - July 3, 2007

  37. PRL 97, 162002 (2006) X (3872)  D0D0p0 Observation of D0D0p0 decay of X(3872) in B decays (B  K D0D0p0) M = 3875.2±0.7+0.3-1.6±0.8 MeV Significance: 6.4s BR(DDp)>40% (from BR(J/ypp)>4.2%) JPC=1++ favored (the DDp decay is expected to be be suppressed for J=2 states) But the measured mass is ~2s above the X(3872) measured mass M. Negrini - Panda Meeting Dubna - July 3, 2007

  38. PRD 73,011101 (2006) Search for X(3872) in B0 decays 211 fb-1 Diquark-antidiquark model predicts the existence of two X(3872) states (Xu and Xd) with slightly different masses:DM~8±3 MeV Different amounts of Xu and Xd produced in B± and B0 decays DD* molecule model predict B0X(3872)K0 to be suppressed by one order of magnitude B0X(3872)Ks B±X(3872)K± 2.5s 6.1s N=61.2±15.3 M=3871.3±0.6±0.1 MeV/c2 N=8.3±4.5 M=3868.6±1.2±0.2 MeV/c2 BR(B0X(3872)Ks)/BR(B±X(3872)K±)=0.50±0.30±0.05 DM=2.7±1.3±0.2 MeV/c2 Not conclusive: more data needed M. Negrini - Panda Meeting Dubna - July 3, 2007

  39. Search for X(3872) charged partners Isospin multiplet: search for charged partners produced in B decays 1. Exclusive reconstruction technique PRD 71, 031501 (2005) B0J/yp-p0K+ B-J/yp-p0Ks No charged partner observed BR(B0X(3872)-K+, X(3872)-J/yp-p0) <5.4·10-6 at 90% CL 3872 3872 BR(B-X(3872)-K0, X(3872)-J/yp-p0) <22·10-6 at 90% CL B0X(3872)+K- 2. Inclusive search using recoil technique PRL 96, 052002 (2006) Inclusive K± momentum on B0 recoil No signal is observed for charged partners BR(B0X (3872)+K-)<5·10-4 at 90% CL 3872 M. Negrini - Panda Meeting Dubna - July 3, 2007

  40. X(3872) • The charmonium interpretation starts being in trouble • The decay to cc1,2g has been searched by Belle but not observed • The decay to J/yh was searched by Babar but not observed • No clear assignment on the basis of predicted mass spectra • All other interpretations assume that the X(3872) has a dominant 4 quarks Fock space component (cc qq) • The main difference between the models is the spatial, color and spin configuration of the state, driven by different assumed dynamics • Different quark dynamics yield different qualitative predictions that need to be tested experimentally M. Negrini - Panda Meeting Dubna - July 3, 2007

  41. X(3872): testing the interaction dynamics Different assumptions yield different predictions that can be tested • (c q)3S=1 (cq)3S=0 + (c q)3S=0 (cq)3S=1 : diquark-antidiquark • model assumes clustering of heavy-light color triplet diquarks • two states Xu and Xd with different masses and two charged partners may exist • mass spectrum of states predicted • (cq)1S=0 (qc)1S=1 + (cq)1S=1 (qc)1S=0 : D0D0* molecule • assumes that D0D0* is the dominant Fock space component • short range (cc)1S=1 (qq)1S=1~J/yr,wcomponent included • a prediction G(J/yp+p-)~G(J/yp+p-p0) is consistent with Belle data • a prediction G(J/yp+p-)~20 G(D0D0p0) is off by 2 orders of magnitude • (cc)8S=1 (qq)8S=1 : molecular model • assumes that the dominant Fock space component are a cc and qq in color octet (similar to case 2) • decays into charmonium with light pseudoscalar mesons are suppressed wrt charmonium with light vector mesons • two neutral states and two charged partners are predicetd No definitive conclusion can be drawn based on present data Failures in predictions can be due to suboptimal tuning of a phenomenological hamiltonian rather than real failure of models M. Negrini - Panda Meeting Dubna - July 3, 2007 an executive summary: hep-ph/0611310

  42. hep-ex/0507019 X(3940) Compute invariant mass recoiling against a J/y in e+e- interactions at s=10.58 GeV Access C=+ states M = 3936±14 MeV G < 50 MeV N = 266±63 events (Signif.: 5s) Candidate for hc''(31S0) X(3940)  DD X(3940)  D*D Mrecoil for events tagged as J/yDD or J/yDD* X(3940)  DD not seen X(3940)  D*D seen M. Negrini - Panda Meeting Dubna - July 3, 2007

  43. Y(3940) PRL 94, 182002 (2005) Reconstruct B in J/ywK decays and count the number of B in M(wJ/y) bins phase space threshold + Breit-Wigner phase space threshold M = 3943±11±13 MeV G = 87±22±26 MeV N = 58±11 events Significance: 8.1s Candidate for cc1' ? M. Negrini - Panda Meeting Dubna - July 3, 2007

  44. Z(3930) PRL 96, 082003 (2006) sin4q (J=2) C=+ defined by production mechanism M = 3929±5±2 MeV G = 29±5±2 MeV N = 64±18 events Significance: 5.3s Consistent with cc2' M. Negrini - Panda Meeting Dubna - July 3, 2007

  45. PRL 95, 142001 (2005) Y(4260) 233 fb-1 gISR e+e- gISR J/yp+p- J/y  e+e-, m+m- e- JPC=1-- ECM<10.58 GeV y’ • Broad structure Y(4260): • N=125±23 • MY=4259±8+2-6 MeV/c2 • GY=88±23+6-4 MeV • JPC=1-- J/y sidebands s’ e+ • Study of J/yp+p- production in ISR • gISR not necessarily detected • Small mass recoiling against final state • Low missing transverse momentum • Well known benchmark channel (y’) S wave phase space MC data M. Negrini - Panda Meeting Dubna - July 3, 2007

  46. No Y(4260) observed in R scan R 4.26 GeV M. Negrini - Panda Meeting Dubna - July 3, 2007

  47. Y(4260) from CLEO-III and Belle Y(4260) also observed in e+e- radiative return at CLEO-III and Belle hep-ex/0606016 hep-ex/0612006 Consistent with Babar M = 4283+17-16±5 MeV G = 70+40-25±4 MeV Mass higher than Babar M = 4295±10+10-3 MeV G = 133±26+13-6 MeV N = 165±24 events M. Negrini - Panda Meeting Dubna - July 3, 2007

  48. PRL 96, 162003 (2006) Y(4260) - CLEO-c Y(4260) observation in e+e- direct scan performed by CLEO-c e+e- cross section at s=4.26 GeV: M. Negrini - Panda Meeting Dubna - July 3, 2007

  49. Search for other Y(4260) decays Preliminary hep-ex/0607083 PRD 73, 012005 (2006) fp+p- DD pp gISR detected gISR not detected gISR detected 232 fb-1 289 fb-1 232 fb-1  sidebands J/y: N=438±22 y(3770) D sidebands J/y Y(4260) Y(4260) y’ y’: N=22±6 No signal No signal No signal Other vector charmonia can be seen in these decay modes M. Negrini - Panda Meeting Dubna - July 3, 2007

  50. hep-ex/0608018 Near threshold e+e- D(*)+D*- cross section • Measurement of near-threshold e+e- D(*)+D*-cross section by Belle using ISR events • No signal of Y(4260) in D(*)+D*-final state • Sharp drop in the D*D* cross section at 4.2 GeV and local minima close to the Y(4260) region 4160 4040 4260 M. Negrini - Panda Meeting Dubna - July 3, 2007

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