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Λ b and heavy states at Tevatron

Λ b and heavy states at Tevatron. by Eduard De La Cruz Burelo University of Michigan On behalf of CDF and D0 collaborations. Outline:. Tevatron & Detectors Λ b quick overview Physics with the Λb Λ b at Tevatron Reconstruction Semileptonic decays channels

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Λ b and heavy states at Tevatron

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  1. Λb and heavy states at Tevatron by Eduard De La Cruz Burelo University of Michigan On behalf of CDF and D0 collaborations Eduard.Burelo@cern.ch

  2. Outline: • Tevatron & Detectors • Λb quick overview • Physics with the Λb • Λb at Tevatron • Reconstruction • Semileptonic decays channels • Full reconstructed decays channels • Mass measurement • Lifetime measurement • Branching Fractions • B** • B decays to narrow D** Eduard.Burelo@cern.ch

  3. Overview on the Λb • Lightest b baryon (udb) • First observed by AU1 collaboration in 1991 in the decay channel Λb→J/ψΛ. • First lifetime measurement from LEP experiments using semileptonic decays in 1992. • Currently produced in high statistics only at Tevatron, (non produced in B factories) Eduard.Burelo@cern.ch

  4. Rich physics program in the Λb • Testing HQE theory in b baryons (lifetime) • Spin role in heavy hyperons (polarization) • CP violation • T violation ( ) • New physics ( ) Eduard.Burelo@cern.ch

  5. Experimental status Eduard.Burelo@cern.ch

  6. C. Tarantino, Monday 20 This was just less of a couple of years ago. LO NLO Just last month !!! HFAG hep-ex/0505100 (*) (*) Includes D0 and CDF Run II measurements Example … This was just less of a couple of years ago. A lot of theoretical work Eduard.Burelo@cern.ch

  7. First step: “Reconstruction”Quite a challenge • For both detectors: • Only charge particles reconstructed • A lot of things going on in the silicon detector Eduard.Burelo@cern.ch

  8. Reconstruction of the Λb • Tevatron is like a B factory, but a dirty one • Only ~5% reconstructable • Zoo of b hadrons: B0, B+, Bs, Bc, b,  b, B** • But: • O(103) higher • Difficult to find other b • In b events , only fb~ 10% (b→X) Eduard.Burelo@cern.ch

  9. Invariant Mass, (GeV/c2) Invariant Mass, (GeV/c2) Λb in full reconstructed channels • Both experiments have clear signal of Eduard.Burelo@cern.ch

  10. Invariant Mass, (GeV/c2) Λb in full reconstructed channels PDG’04 : Seen! Now: clear evidenceΛb→Λ+cπ- ~ 11σ Eduard.Burelo@cern.ch

  11. Λb in semileptonic decays Toward the direct measurement of τ(Λb)/τ(B0d), similar to τ(B+)/τ(B0d) [PRL 94, 182001 (2005)] Eduard.Burelo@cern.ch

  12. Lb Lb Lb After reconstruction … • Mass measurement • Lifetime • Branching fractions • Etcetera … Eduard.Burelo@cern.ch

  13. Λb mass measurement Most precise Lb mass measurement in the world !!! Eduard.Burelo@cern.ch

  14. Lifetime measurement Signal selection λ+ mass distribution (signal + bkg) Fit procedure Models for λ + mass distribution Signal (λ) Background (λ) Background (λ) Models: Simultaneous Mass & lifetime likelihood fit Eduard.Burelo@cern.ch

  15. DØ DØ Λb lifetime[1] First measurement in a full reconstructed decay channel !!! [1] V.M Abazov et al, PRL 94, 100201 (2005) Eduard.Burelo@cern.ch

  16. Eduard.Burelo@cern.ch

  17. Branching fractions: Eduard.Burelo@cern.ch

  18. From PDG: 1.84±0.493 From MC: 1.65±0.03 Branching Fraction: Lb→Lcp From the fit: NΛb=214±19(stat) NB0=790±32(stat) (PDG ’04) Assuming: Eduard.Burelo@cern.ch

  19. Branching Fraction: Bsemi/Bhad First measurement of this ratio !!! Eduard.Burelo@cern.ch

  20. Search for Lb→hh decays • Prediction[2]: • Br (Lb→ pK)=(1.4-1.9)×10-6 • Br (Lb→ pp)=(0.8-1.2)×10-6 compare to Br(B0→Kp)= 18×10-6 • Large CP asymmetries O(10%) expected in b-baryons • Previous best limit from ALEPH • BR(b pK) < 50x10-6 @ 90% • BR(b p) < 50x10-6 @ 90% [2] Mohanta, Phys. Rev. D63:074001,2001 Eduard.Burelo@cern.ch

  21. B** resonances • B meson spectroscopy only well established for ground states B+,B0,Bs. • Few models with precise predictions: mass/widths/BR B1 & B*2 observed by first time as separate states!!! Eduard.Burelo@cern.ch

  22. Semileptonic decays to excited states • BD**mn • BsDs**mn Ds**D*KS Eduard.Burelo@cern.ch

  23. Summary • A lot of new results from Tevatron on theLb baryon • Best mass measurement • First lifetime in full reconstructed channel • Branching fractions by first time measured • More in preparation: • Direct lifetime ratio measurement τ(Λb)/τ(B0) • Others b baryons and studies… • CDF and D0 are looking forward to contribute to a best knowledge of the b baryons. Eduard.Burelo@cern.ch

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