1 / 36

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.

reyesb
Télécharger la présentation

Lifetime and Mixing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related