1. Cano Ay, Johannes Gutenberg Universität, ayc@uni-mainz.de B mixing and flavor oscillations at DØ Cano Ay University Mainz for the DØ Collaboration 23 may 2005 Frontiers in Contemporary Physics III Vanderbilt University Nashville, Tennesse

2. 23 may 2005FCP III, Cano Ay 2 Motivation Mixing and Oscillation Tevatron and DØ Detector Flavor tagging B d Mixing Limit B s Mixing Limit Prospects and plans Summary Outline

3. 23 may 2005FCP III, Cano Ay 3 Motivation The ratio  m s /  m d constrains one side of the unitarity triangle also study CP violation in B s system studied in Kaon and B d system Belle and Babar not sensitiv LHCB not running Tevatron currently only place to study B s Mixing

4. 23 may 2005FCP III, Cano Ay 4 Particle  Antiparticle The transition of a neutral particle into its antiparticle is called Mixing. Mixing

5. 23 may 2005FCP III, Cano Ay 5 Standard Model expectation: Δm s = 14....28ps -1 Δm d = 0.5ps -1 measurement of Δm s /Δm d  V ts /V td constrain unitarity triangle Unitarity triangle

6. 23 may 2005FCP III, Cano Ay 6 Measure  m  asymmetry high uncertainties f(QCD) reduce uncertainties by taking ratio Mixing (2)

7. 23 may 2005FCP III, Cano Ay 7 From the CKM fit:  m s ~ 18 ps -1 Heavy Flavor Averaging group: combined LEP, SLD, CDF1 results  m s > 14.5 ps -1 Mixing (3) Mixing limit obtained using „Amplitude“ Method  Fit data to  Fit for A as a function of  m s o A peaks at 1 for a measurement o Sensitivity given by 1.645  A = 1 (95% CL) o Limit given by A<1-1.645  A (95% CL) flavor tagging performance resolution selection

8. 23 may 2005FCP III, Cano Ay 8 Tevatron Big advantage for B physics : B s meson production

9. 23 may 2005FCP III, Cano Ay 9 Luminosity 460pb -1 200pb -1

10. 23 may 2005FCP III, Cano Ay 10 D0 Detector SMT H-disksSMT F-disksSMT barrels Semileptonic decays: trigger on muon  good muon system reconstruct tracks and vertex  good tracking system

11. 23 may 2005FCP III, Cano Ay 11 Silicon Microstrip Tracker (SMT) Silicon Microstrip Tracker  ~800.000 channels  point resolution: 10  m  Secondary vertex resolution - 40  m (r-  ) - 80  m (r-z) Trackers  Silicon Tracker: |η|<3  Fiber Tracker: |η|<2 Magnetic field 2T

12. 23 may 2005FCP III, Cano Ay 12 Muon Sytem 2 Tesla toroid magnet between A und BC Layer  Muon momentum  propotional drift tubes  pixel scintillators A minidrift tube with cover partially removed Muon system coverage |  |<2 and good shielding

13. 23 may 2005FCP III, Cano Ay 13 B production Fermilab: σ ≈ O(100μb) L1 Trigger acceptance (DØ: Muon) : σ ≈ O(3-5μb) B production and decay B 0 s → D - s μ μ D - s →  (K + K - )  - B 0 d → D * (2010) - µ + µ D * (2010) -  D 0 (K +  - )  - B + → D 0 µ + µ D 0  K -  + Used Decays:

14. 23 may 2005FCP III, Cano Ay 14 Flavor tagging 1. Soft Lepton Tag (SLT) 2. Opposite Jet charge (Jetq) 3. Same Side Tag (currently only used for B d ) Flavor tagging : determine b-flavor at production time! oscillated not oscillated reconstructed sideopposite side

15. 23 may 2005FCP III, Cano Ay 15 B d Sample angle and distance : distance PV  D Vertex (xy-plane) D Vertex not before B Vertex Angle between PV  B Vertex and PV  D Vertex Charged tracks: p T > 0.65 GeV/c impact parameter significance: Single µ data – 200pb -1

16. 23 may 2005FCP III, Cano Ay 16 B d Mixing Limit Asymmetry SLT : D 0 = (44.8  5.1)% Jetq+SST: D 0 = (14.9  1.5)% Jetq+SST: D  = 27.9%  m d =0.456  0.034ps -1 (stat)  0.025ps -1 (syst) consistent with  m d =0.502  0.007ps -1 (world average)

17. 23 may 2005FCP III, Cano Ay 17 Currently only using a single semileptonic decay of the Bs B s  D s  X (Ds  p) (   K K) Using  + SV vertex tag (Opposite side tag, independent of reconstructed side) The goal was to develop tools and to allow a baseline to build on for the future B s Mixing analysis procedure

18. 23 may 2005FCP III, Cano Ay 18 angle and distance : distance PV  D Vertex (xy-plane) D Vertex not before B Vertex Angle between PV  B Vertex and PV  D Vertex Angle between PV  D Vertex and D momentum … Charged tracks: p T > 0.7 GeV/c impact parameter significance Invariant KK mass 1.006 < M(KK) < 1.30 B s Sample

19. 23 may 2005FCP III, Cano Ay 19 Inputs to the fitting procedure MC Sample composition K-factor to take non-reconstructed particles into account Efficiencies Visible Proper Decay Length (VPDL) resolution VPDL resolution has been tuned using data Dilution from B 0 d and B + u semileptonic samples B s Mixing fitting procedure

20. 23 may 2005FCP III, Cano Ay 20 DecaySample composition B s → D s μν20.6% B s → D * s μν57.2% B s → D * 0s μν1.4% B s → D * 1s μν2.9% Bs→DsDsXBs→DsDsX11.3% B 0 → D s DX3.2% B - → D s DX3.4% cc estimated at ~ 3.5 ± 2.5 % VPDL (cm) Efficiency drop at low VPDL due to impact parameter cuts on tracks from D s decay Sample Composition and efficiency

21. 23 may 2005FCP III, Cano Ay 21 Decay B s → D s μν0.878 B s → D * s μν0.857 B s → D * 0s μν0.829 B s → D * 1s μν0.817 Bs→DsDsXBs→DsDsX0.738 B 0 → D s DX0.681 B - → D s DX0.687 K K x VPDL K-factors

22. 23 may 2005FCP III, Cano Ay 22 VPDL resolution parametrized with three Gaussians Track by track smearing dependant on track momentum and polar angle Tuning results with one scale factor 1.095 VPDL Resolution: MC tuned with data no smearing after smearing VPDL rec – VPDL gen [cm]

23. 23 may 2005FCP III, Cano Ay 23 D Ø Run II preliminary Dilution SLT + SV Jetq : D 0 = (39.0  3.2)% D  = (47.6  2.0)%  use mean : D avr =(45.4  1.7)% for B s asymmetry

24. 23 may 2005FCP III, Cano Ay 24 No obvious oscillations in the μD s sample  m s > 5.0 ps -1 at 95% CL using “Amplitude” method B s Mixing Limit

25. 23 may 2005FCP III, Cano Ay 25 Scaling of the current sensitivity with luminosity - if analysis remains unchanged - with expected improvements Sensitivity vs. Luminosity Semileptonic channels

26. 23 may 2005FCP III, Cano Ay 26 Use both semileptonic and hadronic Bs samples More statistics in semileptonics Better proper decay time resolution in hadronics (no ) DZero has access to hadronic Bs sample triggering on opposite side muon Muon is used as high purity tag Detector addition in fall: “Layer 0” Silicon detector Proposal to increase rate to tape from 50 to 100 Hz in fall sample limited by L3 trigger and offline CPU – expect large gain in yield thanks to dedicated B-physics bandwidth Bs Mixing Projections

27. 23 may 2005FCP III, Cano Ay 27 Summary measured, which is in agreement with world average  m d =0.456  0.034ps -1 (stat)  0.025ps -1 (syst) developed a procedure to measure  m s using semileptonic channel B s  D s (  )    m s > 5.0ps -1 at 95% CL will add more semileptonic channels and hadronic channels „Layer 0“ Silicon detector and increasing L3 rate will improve resolution and increase statistics