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Lifetime and Mixing

Lifetime and Mixing. Chunlei Liu / University of Pittsburgh On behalf of CDF and D0 collaborations FPCP 2008 May 5-9. Part I Lifetime Motivation and Experiments B 0 s , B c lifetimes Part II Mixing B 0 s mixing from D0 D 0 mixing from CDF.

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Lifetime and Mixing

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  1. Lifetime and Mixing Chunlei Liu / University of Pittsburgh On behalf of CDF and D0 collaborations FPCP 2008 May 5-9

  2. Part I Lifetime • Motivation and Experiments • B0s , Bc lifetimes Part II Mixing • B0s mixing from D0 • D0 mixing from CDF

  3. Decay of B Hadrons kinetic and chromomagnetic operator weak annihilation and Pauli interference Pauli interference prolongs lifetimes: +5% for B+, +3% for Lb Spectator model: all b hadron lifetimes are equal. Heavy Quark Expansion (HQE): Lifetime ratios are better predicted: t(B+)/t(B0), t(Bs)/t(B0), t(Lb)/t(B0)… Weak annihilation or scattering reduces lifetimes -7% Lb

  4. The Bc - Doubly Heavy Meson • Doubly heavy with band c quark – interesting lab for studying QCD • Both quarks decay or annihilate, shorter lifetime than light B mesons theory prediction: t(Bc):0.47 - 0.59 ps arXiv:hep-ph/0308214v1 Phy Rev. D 64, 14003 (2001) Phy Lett. B 452, 129 (1999) hep-ph/0002127 ( and references within)

  5. B0s Lifetime and Decay Width Difference b s s W W B0s→J/yf W c s c • Eigenstates: Bslight and Bsheavy => GL and GH • Gs= (GL+GH)/2 , DG = GL-GH • Two kinds of lifetime measurements: • Measure 1/Gs and DG directly (need to identify CP eigenstates) • Treat GL and GH together as one exponential, measure t • e.g flavor specific channel:

  6. Combine ts and DG DG: theoretically calculable and sensitive to new Physics Probe to New Physics : DG= 2|G12|cos(fs)

  7. Latest HFAG (by 03/08) • New measurements today: • Bs lifetime –direct measurement • Bs lifetime – flavor specific • Bc lifetime Theory references: PRD 68, 114006 (2003) PRD 70, 094031 (2004) hep-ph/0705.3802 (2007)

  8. Booster CDF DØ Tevatron p source Main Injector & Recycler Tevatron • pp collisions at 1.96 TeV • 3.4 fb–1 data on tape (recorded at D0) • Initial instantaneous luminosity up to 3x1032cm–2s–1 Apr 2002 – Apr 2008

  9. CDF II DetectorDØ Detector • Central tracking: silicon vertex detector drift chamber • => dpT/pT = 0.0015 pT • excellent vertex resolution • Particle identification: dE/dX and TOF • Excellent muon coverage • Goodtracker coverage • Silicon layer 0 installed in 2006 improves track parameter resolution tracker

  10. q Measure ts and DG from B0s→J/yf ct=L/bg =Lxy/sinq/bg =LxyM/PT CP conservation (bs=0) |BsH> : CP odd eigenstate ~ 25% |BsL> : CP even eigenstate ~ 75% S, D waves: CP even P wave: CP odd Angular distribution in transversity basis => separate CP eigenstates

  11. Events Selection at CDF/D0 • Di-muon trigger • Neural Network selection at CDF ~ 2500 signal events • Cuts based selection at D0 ~ 2000 signal events

  12. Measure ts and DG • (bs free) • =1.52 ± 0.05(stat)±0.01(syst) ps DG=0.19±0.07(stat) +0.02-0.01(syst) ps-1 • (bs=0) t=1.53 ± 0.06(stat) ps DG=0.14 ± 0.07(stat) ps-1 • (arXiv:/0802.2255[hep-ex]) (bs=0) t=1.52 ± 0.04(stat) ± 0.02(syst) ps DG=0.08 ± 0.06(stat) ± 0.01(syst) ps-1 World’s best measurement! Phys. Rev. Lett. 100, 121803 (2008)

  13. Bs Lifetime Measurement from Bs→ Ds+(fp)p- X - CDF x2 stats fully and partially reconstructed channel such as: Bs→ Ds-1r(p+p0) Double statistics! “K” factor accounts for missing momentum and mass Extensive test on B0, B+ control samples

  14. Events Selection and Fit Strategy • Data (1.3 fb-1) collected by displaced-vertex trigger ( 120mm<d0<1mm ) • ~ 1100 fully reconstructed events • ~ 2000 partially reconstructed events • => cut on lifetime ( events with ct<d0 removed) • modeled with “trigger efficiency curve” from MC • Two-step fit, 1)mass fit • => relative fraction of various modes and background • 2) lifetime fit (shape from MC, fraction from mass fit) • => extract lifetime only

  15. Lifetime Result (CDF) • Fix fractions from mass fit • t(Bs) only free parameter • = 1.518 ± 0.041(stat.) ± 0.025(syst.) ps (http://www-cdf.fnal.gov/physics/new/bottom/080207.blessed-bs-lifetime/) • Lifetime for control samples: • B0→ D-(K+p-p-) p+ B0→ D*-(D0(K+p-)p-) p+ B+ →D0(K+p-) p+ • Agrees well with PDG D0 had Bs semileptonic lifetime in 2006 from Bs→Ds-m+nX t=1.398±0.044(stat)+0.028-0.025(syst) ps PRL 97, 241801 (2006)

  16. Bc Semileptonic Lifetime Missing momentum, correct pseudo-lifetime: ct= K x ct* K= pT(J/y l)/ pT(Bc) • Main challenge is multiple backgrounds: • real J/Ψ + fake lepton • fake J/Ψ + real lepton • real J/Ψ + real lepton → from bb events • prompt J/Ψ + lepton • residual conversion (J/y+e only)

  17. Bc→J/y+m+X from D0 (1.35 fb-1) Mass – lifetime simultaneous fit used to disentangle small signal fraction among large fraction of backgrounds http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/B/B52/

  18. Bc→J/y+l+X from CDF (1.0 fb-1) Lifetime fit only Muon channel Electron channel ct=179.1+32.6-27.2(stat) mm ct=121.7+18.0-16.3(stat) mm combined (by likelihood): t=0.475+0.052-0.049(stat) ± 0.018(syst) ps(http://www-cdf.fnal.gov/physics/new/bottom/080327.blessed-BC_LT_SemiLeptonic/)

  19. Combine Bc Lifetime from D0 and CDF Bc lifetime measurements have been exclusive to Tevatron Weighted average: t=0.459 ± 0.037 ps Theory prediction: t=0.47 – 0.59 ps

  20. Part I Lifetime • Motivation and Experiments • B0s , Bc lifetimes Part II Mixing • B0s mixing from D0 • D0 mixing from CDF

  21. B0s Mixing • two eigenstates and • Dms mH – mL , Gs( GH+GL)/2,DGGL– GH • DmsTheo =19.3 ± 6.4 ± 1.9 • (arXiv: 0705.3802/hep-ph) • Dms/Dmd ∝ |Vts|2/|Vtd|2 • CDF measured at: 17.77 ± 0.10(stat) ± 0.07(syst) ps • Show D0 new result today !

  22. Dms Measurement Strategy Opposite Side Same Side

  23. Final States Reconstruction at D0 Data collected by inclusive single and di-muon triggers, 2.4 fb-1 Final cuts maximizing S/ sqrt(S+B) D0 Run IIa D0 Run IIb innermost layer of silicon added resolution improved

  24. Measure Dms at D0 • Introduce amplitude, P(t) ~ 1AD cos(Dmst) • Fitfor A at different Dms Δms = 18.53± 0.93(stat) ± 0.30(syst) ps-1 2.9 s significance ( DO conference note 5618) Agrees with what CDF measured in 2006: Δms = 17.77 ± 0.10(stat) ± 0.07(syst) ps-1

  25. DM/GDG/G discovered K0 0.474 0.9971964 B0 0.77 <0.01 1987 Bs 27 0.15 2006 D0 < 0.01< 0.01 2007 D0 Mixing D0 mixing in SM occurs through either: ‘short range’ processes ‘long range’ processes (negligible in SM) • Recent D0 mixing evidence : • Compare D0 → ππ, KK (CP eigenstates) with D0 → Kπ(Belle) • 2) Comparedoubly Cabibbo suppressed (DCS) D0 →K+π- with Cabibbo favored (CF) D0 →K-π+(Babar ) Lifetime ratio: where x=DM/DG , y=DG/2G, d is strong phase between DCS and CF modes

  26. Evidence for D0 Mixing at CDF (1.5 fb-1) CDF : probe longer D0 lifetime than B factories 3.8s significance comparing DCS D0 →K+π- to CF D0 →K-π+ RD (10-3)=3.04±0.55 x’2(10-3)=-0.12±0.35 y’(10-3)= 8.5±7.6 (Phys.Rev.Lett.100:121802,2008 ) Lifetime ratio fit Bayesian probability 1-4s contour: closed circle: best fit value open diamond: highest probability point physically allowed (x’2≥0) cross : no mixing point 3.8s

  27. Conclusion • Best Bst and DG measurement in the world • Bc lifetime provide better constraint for theory • Bs mixing from D0 confirms CDF measurement • D0 mixing evidence from hadron collider • Expect new Lb lifetime result for the summer

  28. Back Up

  29. Angular Analysis in Transversity Basis ●Bs->J/yf is P -> VV decay ➔ 3 possible angular momenta: S, D wave: CP even P wave : CP odd ● Separation by angular distribution ➢ Transversity angles q, f,y 

  30. B0s Systematics and Cross Check Systematics at CDF: 1) Background angular distribution 2) Mass model 3) Lifetime resolution function 4) B0 cross feed 5) Detector acceptance 6) Silicon detector alignment Cross check sample at CDF: B0→J/y K*0 for angular analyis Lifetime: td= 1.52 ± 0.02(stat) ± 0.02(syst) ps Systematics at D0: 1) Procedure test 2) Acceptance 3) Reconstruction algorithm 4) Background model 5) Detector alignment

  31. Bs→ J/yf angular distribution

  32. B0 → J/y K*0 ctd = 456 +/- 6 (stat) +/- 6 (syst) μm |A0|2 = 0.569 +/- 0.009 (stat) +/- 0.009 (syst) |A|||2 = 0.211 +/- 0.012 (stat) +/- 0.006 (syst) δ|| = -2.97 +/- 0.08 (stat) +/- 0.03 (syst) δ⊥ = 2.97 +/- 0.06 (stat) +/- 0.01 (syst)

  33. Mass components: Single B templates (MC): (signal): Bs→ Ds(fp) X (bkgd): B0, B+, Lb Real D + track (background): template comes from fit to wrong-sign sample Ds-p- Fake D + track (background): template comes from D sidebands

  34. Bc Background Summary at CDF

  35. decay mode CDF lifetime (ps), 1 fb-1 DØ lifetime (ps), 1.3 fb-1 x expected soon x updateexpected soon x One word about Λb LifetimeStatus • DØ measurements are in agreement with the theoretical predictions and with • the world average • CDF measurement in is ~3s highw.r.t world average • Expect CDF measurement updates very soon

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