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New States Containing Charm at B A B AR

New States Containing Charm at B A B AR. PHENO 06 Symposium A.J. Edwards - Stanford University May 15. Outline. Λ c (2940) + A new charm baryon above the Dp threshold. Ξ cc + and Ξ cc ++ Are double-charm baryons among us? D* sJ (2317) + and D sJ (2458) +

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New States Containing Charm at B A B AR

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  1. New States Containing Charm at BABAR PHENO 06 Symposium A.J. Edwards - Stanford University May 15

  2. Outline • Λc(2940)+ • A new charm baryon above the Dp threshold. • Ξcc+ and Ξcc++ • Are double-charm baryons among us? • D*sJ(2317)+ and DsJ(2458)+ • An update on newly discovered cs states that contradict theoretical predictions for mass. • X(3872) and Y(4260) • New charmonia? 2

  3. Λc(2940)+ 3

  4. Charm Baryon Spectroscopy Λc(2940)+ • Two new observations in cc continuum of particles with decays to D0p • The first observation of Λc(2880)+→ D0p • Discovery of Λc(2940)+ in the same decay mode Λc(2880)+ D0p Threshold π 4

  5. Λc(2940)+ hep-ex/0603052 Λc(2880)+ Λc(2940)+ M = (2939.8±1.3±1.0) MeV/c2 Γ = (17.5±5.2±5.9) MeV Λc(2940)+ Λc(2880)+ M = (2881.9±0.1±0.5) MeV/c2 Γ = (5.8±1.5±1.1) MeV Wrong sign D0p D0 mass sidebands 5

  6. Λc(2940)+ hep-ex/0603052 Sascha Migura et al. • Three different spin-parity states predicted around a mass of 2940 MeV/c2: (1/2)+, (1/2)–, and (3/2)–. • The Λc(2880)+ is near a predicted (3/2)– state. No significant branching fraction to Λcπ+π– is observed for Λc(2940)+. No known reason for the suppression. No Σciso-partner states found in D+p spectrum. 6

  7. Doubly Charmed Baryons 7

  8. SU(4) 20'-plet Charm Isospin SELEX Doubly Charmed Baryons • Theoretically Ξcc & Ωcc should exist. • The SELEX experiment (hyperon beam) reports evidence for them. (~1,630 Λc) • The FOCUS experiment (photon beam) sees no evidence for them. (~19,500 Λc) Strangeness Can they be found at BABAR? Phys.Lett.B628:18-24,2005 • Large numbers of single charm baryons. • ~600,000 Λc+ and ~12,000 Ξc0 • Double charm baryon e+e– cross section predictions: 1 - 250 fb • Theoretical branching fractions • Λc+K-π+, Λc+K-π+π+, Ξc0π+, Ξc0π-π+: ~ a few percent SELEX sees an excess of Ξcc+ candidates in two decay modes. 8

  9. Doubly Charmed Baryons Λc+K–π+ p*> 0 GeV/c 95% C.L. Λc+K–π+ p*>2.3 GeV/c 95% C.L. Λc+K–π+π– p*> 0 GeV/c 95% C.L. Λc+K–π+π– p*>2.3 GeV/c < 95% C.L. 9

  10. Doubly Charmed Baryons Ξc0π+ p*> 0 GeV/c < 2.0 fb 95% C.L. Ξc0π+ p*> 2 GeV/c < 1.3 fb 95% C.L. Ξc0π+π+p*> 0 GeV/c 95% C.L. < 5.6 fb Ξc0π+π+p*> 2 GeV/c < 3.4 fb 95% C.L. 10

  11. DsJ*(2317) and DsJ(2460) 11

  12. Both masses unexpectedly low: below DK and D*K threshold, respectively Only isospin-violating or electromagnetic decays kinematically allowed  narrow widths Decay pattern and decay angular distributions consistent with interpretation as JP=0+ and JP=1+, respectively Charm-Strange Mesons • DsJ*(2317) and DsJ(2460) first observed by BABAR and CLEO in cc continuum events, and by Belle in B decays CLEO: 13.5 fb-1 PRD 68, 032002 (2003) Belle: 124M BB PRL 91, 262002 (2003) BABAR: 91 fb-1 PRL 90, 242001 (2003) 12

  13. Charm-Strange Mesons • Assuming DsJ*(2317) and DsJ(2460) are 0+ and 1+ respectively, the decay channels below are allowed or forbidden as indicated. • All of the above decay modes have been searched for. • All “Seen” modes are also “Allowed” 13

  14. D*sJ(2317)+ • Original D*sJ(2317) discovery mode update • No indication of neutral or doubly-charged signal, ruling out some exotic interpretations N=3180±80 2 MeV/c2 Bins Ds+π– Circles: Ds sidebands Ds*(2112) reflection Ds+π+ Dark shade: DsJ(2460) reflection 2317 MeV/c2 14

  15. DsJ(2460)+Ds+π0 Dark shade: DsJ*(2317)+ reflection Light shade: Ds*(2112)+ reflection DsJ(2460) → Ds+π+π- Open points: Ds sidebands DsJ*(2317) N=123±15 N=6±3 DsJ(2460)+Ds+ DsJ(2460)+ • DsJ(2460) decay channels • Original: Ds* π0,Ds*→Ds+  • Additional: Ds+ • Additional: Ds+π+π- N=560±40 N=920±60 15

  16. DsJ(2460)+ • Combining the three DsJ(2460)+ decay channels • New branching ratios are well measured • Limits are set for additional allowed/forbidden decay channels. 16

  17. p e- D* Breco e+ Bsignal D* X DsJ(2460)+ Absolute Branching Fractions • Sample with one B fully reconstructed (Breco) • Study decays of other BD(*)+,0 X • Observe DsJ(2460)+ signals in the recoil mass (mX) hep-ex/0604030 = (0.88 ± 0.20 ± 0.14) % 17

  18. DsJ(2460)+ Absolute Branching Fractions • Combine with previously measured product branching fractions • Sum of known branching fractions: 0.76±0.17 18

  19. X(3872) and Y(4260) 19

  20. X(3872) Recently updated result from BABAR • Initial discovery of B– → X(3872)K– → J/ψπ+π– K– by Belle • Confirmed by CDF andBABAR PRD 73, 011101 (2006) N=49±8 N=61±15 (6.1 σ) hep-ex/0505038 B± only Solid Hist.: mES sidebands 20

  21. X(3872) • X(3872)+-J/ is an isospin-violating decay • No charged partners found PRD 71, 031501 (2005) • New decay mode observed • X(3872) → γJ/ψ • This implies that X(3872) is a C=+ state N=19±6 (3.4 σ) 21

  22. (2S) Y(4260) • Searching for X(3872) in ISR events but found Y(4260) Peak cross section: σ(e+e-Y)=(51±12) pb 22

  23. Y(4260) CLEO results confirm Y(4260) • Consistent with BABAR cross section • No J/ψπ0 decay signal seen hep-ex/0602034 N=37 (11 σ) N=8 (5.1 σ) 23

  24. 3770 4260 Y(4260) • Searches for decays of Y(4260) to DD, φππ, and pp all do not find signal. M(K+K-) PRD 73, 012005 (2006) Y(4260) 24

  25. Summary 25

  26. Summary • Charmed spectroscopy at BABAR is very active and pushing the boundaries of our knowledge. • Λc(2940)+ : A new charmed baryon above the Dp threshold. • Ξcc+ and Ξcc++ are searched for but none seen by BABAR • An update on newly discovered cs states that challenge theoretical predictions for mass • X(3872) and Y(4260) discoveries and updates 26

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