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B hadrons lifetimes @ Tevatron

B hadrons lifetimes @ Tevatron. By Eduard De La Cruz Burelo University of Michigan On behalf of the CDF and D0 collaborations. BEACH 2006. Lancaster University UK, 2-8 July, 2006. CDF and DØ Detectors. Complete description in other talks :

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B hadrons lifetimes @ Tevatron

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  1. B hadrons lifetimes @ Tevatron By Eduard De La Cruz Burelo University of Michigan On behalf of the CDF and D0 collaborations BEACH 2006 Lancaster University UK, 2-8 July, 2006

  2. CDF and DØ Detectors • Complete description in other talks : • S. Donati, CDF detector and triggers for B Physics • L. Welty, D0 detector and triggers for B Physics

  3. Outline • In this talk • Bs lifetime in semileptonic decays • Bc lifetime • Λb lifetime • CDF/D0 measurements no presented here • B+,B0, and Bs lifetime in B→J/ψX decays • B+,B0, and Bs lifetime in hadronic decays • B+ and B0 lifetime in semileptonic decays • Bs lifetime in Bs→K+K- • Summary, conclusions and future measurements…

  4. Motivation THEORY • Testing HQE, where light quarks are included via 1/mb perturbative expansions. • Expect some differences between lifetimes of different species: • τ(B+) ≥ τ(B0) ≈ τ(Bs) > τ(Λb) >> τ(Bc) • Lifetime ratios are usually reported since it reduces uncertainties • Currently b-baryons are accessible at high statistics at the Tevatron. EXPERIMENT C. Tarantino, hep-ph/0310241

  5. Current status HFAG hep-ex/0505100 Measurements from CDF/D0 no presented in this talk (just to compare): • B+,B0 and Bs mesons, excl. reconstructed in hadronic decays (CDF 360 pb-1) • τ(B+) = 1.66 ± 0.03(stat) ± 0.01(syst) ps • τ(B0) = 1.51 ± 0.02(stat) ± 0.01(syst) ps • τ(Bs) = 1.60 ± 0.10(stat) ± 0.02(syst) ps • τ(B+)/τ(B0) = 1.10 ± 0.02(stat) ± 0.01(syst) • τ(Bs)/τ(B0) = 1.06 ± 0.07(stat) ± 0.01(syst) • Direct measurement of the lifetime ratio (D0 440 pb-1) • τ(B+)/τ(B0) = 1.080 ± 0.016(stat) ± 0.014(syst)

  6. LB B decay Vertex Primary vertex Lifetime measure techniques • Fully reconstructed decay: • Using proper decay length method: Transverse component of the boost The distribution of  is related to the lifetime of the B “R” is the resolution function

  7. Lifetime measure techniques • Partially reconstructed decay: • Using pseudo-proper decay length method: • pT(semi) : Transverse momentum of the semi-reconstructed decay • K : factor to account for the momentum of missing particles in the B decay. Extracted from MC Signal p.d.f.: “R” is the resolution function

  8. Bs system Schrödinger equation: Most general eigenstates: Heavy (H) and light (L) Bs eigenstates are expected to have different widths • Relation of matrix elements to decay and oscillation parameters: • J. Walder, Bs oscillation measurements at D0 • G. Salamanna, Bs oscillation measurements at CDF • Kin Yip, Measurements of Bs lifetime difference at Tevatron

  9. Bs lifetime in semileptonic decays • CDF and D have measured the Bs lifetime in the semileptonic decay Bs→DslX, l=e, (DØ use only ) • It is a equal mixture of CP states, extra constraint to ΔΓ/Γ: • Large statistics from muon triggers τm(Bs) is the mean Bs lifetime obtained from a fit assuming a single exponential decay – I. Dunietz et al, Phys. Rev. D63 114015 (2001) -.

  10. signal ~ 1232 Bs semileptonic samples CDF: 8 GeV single lepton trigger (muons and electrons) D0: Muons with pT>2 GeV

  11. Primary vertex Pseudo-proper decay length: • K factor is extracted from MC • Charm and bottom background are included in the fit

  12. Bs lifetime results: • CDF 360 pb-1 • D0 400 pb-1 • World average(2006): Best world measurement !!!. Hep-ex/0604046

  13. Constraining ΔΓ/Γ One sigma contours of flavor-specific decays lifetime, including D0 measurement. For ΔΓ/Γ and Bs→K+K- lifetime see: • Kin Yip, Measurements of Bs lifetime difference at Tevatron R. Van Kooten:hep-ex/0606005

  14. Λb lifetime in the fully reconstructed decay Λb→J/ψΛ • Lightest b baryon (udb) • World average lifetime dominated by measurements in semileptonic decay channels, where Λbis not fully reconstructed. • Currently produced in high statistics only at Tevatron, (no produced in B factories) • Testing Heavy Quark Expansion theory in three quarks system.

  15. Beam line   Λ π p  distribution related to the Λb lifetime: R is the detector resolution

  16. Measurement method Signal selection λ+ mass distribution (signal + bkg) Fitting procedure Models for λ + mass distribution B0J/ KS is used as a control sample due to its similar topology, lifetime measured at the same time. It can be used to compute the lifetime ratio τ(Λb)/ τ(B0) Simultaneous Mass & lifetime likelihood fit • Signal p.d.f.: • Exponential decay convoluted with the resolution function • Background p.d.f.: • Resolution for zero lifetime component • Exponential decays for short and long-lived bkg.

  17. DØ Λb mass signal L=250 pb-1 PRL 94, 102001 (2005)

  18. DØ DØ D0 Λb lifetime measurement Measurement in 250 pb-1 of data, in the decay: V.M Abazov et al, PRL 94, 100201 (2005)

  19. New CDF’s Λb lifetime measurement World average: τ(Λb)=1.23 ± 0.08 ps First time the Λb lifetime is measured as large as to the B0 lifetime. New precision is at the level of the world average.

  20. Cross check for lifetime measurement (CDF)

  21. PDG 2004 Excludes new CDF result

  22. e    u d b c c c J/Ψ→µµ Bc lifetime • Bound state of two heavy quarks (b and c) • Bc is the only meson with different heavy flavors • Only weak decays possible • Low production rate B0:B+:Bs:Λb ≈ 40:40:10:10, Bc~0.5% • Difficult to select due to its short lifetime • See dedicated talk to Bc: • A. Rahaman, New results on Bc in Tevatron

  23. Lifetime extracted from Bc → J/Ψlν samples CDF in J/Ψe channel (360 pb-1 ) DØ in J/Ψµ channel (210 pb-1 )

  24. Bc lifetime measurement Lifetime measurement using pseudo-proper decay length, K factor from MC CDF: lifetime measured in J/Ψe channel (360 pb-1 ) DØ: lifetime measured in J/Ψµ channel (210 pb-1 ) Prediction: 0.55 ±0.15 ps V. Kiselev, hep-ph/0308214

  25. Summary • A lot of lifetime measurements from the Run II of Tevatron. No possible to cover all of them in this talk. • New CDF Λb lifetime is surprisinghigh compareto the world average. New measurements in complementary channels to come to support or cross check this. • Best world measurement of Bs lifetime in semileptonic decay, an extra constraint to ΔΓ/Γand the possibility of new physics in the Bs system. • Bc lifetime measurement consistent with prediction. Measurements in fully reconstructed decay channels in the future will help to improve the precision.

  26. Future measurements… • More results in the future: • DØ • Updated b J/ Lifetime with 1 fb-1 • Measurement of b Lifetime in semileptonic decays using 1 fb-1 • CDF • Lifetime measurement in b c • Update of lifetime of B hadrons in B J/ X channels using 1 fb-1 This measurements will cross check the CDF lifetime measurement what is 3σ away from the world average.

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