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Flavor Tagging at Tevatron, incl. calibration and Control BEAUTY 2006 (Keble College,Oxford)

Flavor Tagging at Tevatron, incl. calibration and Control BEAUTY 2006 (Keble College,Oxford). Tania Moulik, University of Kansas (on behalf of CDF and DØ collaboration). Outline. Introduction Soft Lepton Identification at CDF and DØ Opposite side flavor Tagging

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Flavor Tagging at Tevatron, incl. calibration and Control BEAUTY 2006 (Keble College,Oxford)

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  1. Flavor Tagging at Tevatron, incl. calibration and ControlBEAUTY 2006 (Keble College,Oxford) Tania Moulik, University of Kansas (on behalf of CDF and DØ collaboration) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  2. Outline • Introduction • Soft Lepton Identification at CDF and DØ • Opposite side flavor Tagging • Development of flavor tagging at CDF • Development of flavor tagging at DØ. • Same side flavor Tagging • Tagger Calibration (Bd Mixing) • Results and Current Status • Conclusions. Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  3. Introduction • Flavor Tagging is important for analyses where one needs to identify the flavor of B meson at “production” ( constituent b is “quark” or “anti-quark” ?) • For e.g., a neutral B meson can mix, hence, the decay product of the B does not identify the flavor “at production”. • The flavor at “decay” is determined from the B decay product. • The figure of merit of flavor tagger : • Efficiency (e) = N(No. of Tags)/N(Reconstructed B’s) • Dilution (D) = 2 * P – 1, where P = N(right sign)/N(total tags) • Goal of a flavor tagger is to maximiseeD2 Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  4. Flavor Tagger types • Opposite side Tagging – Use the decay signature of the other B in the event. • Lepton Tagging, Jet Charge Tagging (Charge content of the b jet) , Opposite side kaon tag (b  c  s (K-) (B0 K-)) • Same Side Tagging – Use fragmentation track associated to the vertexing side B particle Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  5. Trigger CDF 2-Track Trigger pT (trk) > 2.0 GeV d0 (trk) > 100 mm Df < 135o Hadronic modes • CDF Displaced track + lepton (e, m) • d0(trk) > 120 mm • pT (lepton) > 4.0 GeV • Semileptonic modes Single inclusive muon trigger at DØ Multiple triggers with different pT thresholds. A muon + pT (trk) > 1.5/3.0/4.0/5.0 GeV, turned on depending on luminosity. Dimuon Trigger – Other muon gives the flavor tag (pT > 1.5 GeV) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  6. Lepton Identification Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  7. Muon Id (Muon Chambers) • Muon Detector at CDF • Muon Detector at DØ Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  8. Muon Id at CDF & D0 • Likelihood developed for low pT muon identification. Worry about bkg. for CMU only muons. use variables : • Track - Muon Stub matching in x,z,f • energy deposits in EM and HAD calorimeter. • Signal PDF : using muons from J/Y  m+m- • Bkg. PDF : using Ks  p+p-, D0K+p-, L  p p • Cuts on muon stub - track matching at D0. Negligible punch through due to presence of toroid (require muon passed toroid) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  9. CDF Calorimeter 24 EM Modules. Position at shower max using cathode strip chamber - charge deposition on orthogonal strips and wires. D0 Liquid argon calorimeter Central (|h| < 1) (32 EM Mod.) Forward upto (|h| = 4) h x f = 0.1 x 0.1 (finer in third layer) Preshower added in runII – three layers of scintillators with WLS readout. Electron Id (Calorimeters) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  10. FH1 EM FH1 EM Soft electron Id • Soft electron reconstruction separate from standard calorimeter reconstruction. Start with track, extrapolate to calorimeter and cluster towers around track in a narrower Dh x Df region. • Study performance using signal : ge+e- and bkg : Ksp+ p- e e p p D0 detector x-ray using conversions Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  11. Soft electron Id • CDF developed likelihood to discriminate signal and background. • Simple cuts at DØ(EMF, E/P, preshower energy) D0 Kinematic Cuts : pT > 2.0 GeV |h| < 1.1 CDF Kinematic Cuts : pT > 2.0 GeV |h| < 1.0 Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  12. OST development at CDF • Use l+SVT as trigger samples (All inclusive, huge statistics). ( l gives B flavor at decay) • B-decay on the trigger side can mix and can undergo wrong-sign sequential decays. Reduces dilution on tag side.Study Sample composition in MC -- fraction of RS/WS tags on trigger side (Use MC truth) . • Proceed with tagging  'true' tagger dilution. = “raw” tagger dilution/”trigger” side dilution. d = |d0| sign(d0.pl+SVT) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  13. Opposite Side Flavor Tagging Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  14. Lepton Tag event-by-event dilution • Parametrise dilution as function of pTrel (transverse momentum of lepton w.r.t to lepton jet) and likelihood cut. • Expected event-by-event dilution  D(pTrel, L value) Muon Tagger Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  15. Jet Charge tagging at CDF Form track-based jets Track clusterig NN Inputs d0/sd0, d0signed, pT, DRB… NN (Neural network) to assign “b”-ness prob. for tracks in each jet (TrackNet Prob) Ntrprob> 50%,SVc2, NtrSV,pT, Jet mass… NN prob. for “b”-ness of each jet If Multiple jets found, most prob. one chosen Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  16. Jet Charge Tagging at CDF • Divide jets in 3 classes. • Jets with secondary vertex having Lxy/sLxy > 3 • Jets failing Class1 with at least 1 track with trackNet prob > 50% • Not 1 or 2. • Calibrate dilution as function of |Qjet| * Pnn • Overall eD2 : 0.917  0.031 % e+SVT 0.938  0.029 % m+SVT Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  17. OST development at DØ • Construct PDF’s for variables discriminating between b and b • Use B+  D0 m+ n X decay data sample (No mixing, b flavor known). • Remove B0 oscillated events (small decay length < 500 mm) (98% B+)). • q(brec) == q(m) • Get tag on opposite side and construct PDF’s. • Electron/Muon jet charge Use tracks around electron/muon DR (m/e, track) < 0.7 Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  18. Flavor Tagging development at DØ Events with muon • Other variables used: • Secondary vertex Charge • Event Charge Events without muon • = 0.6 after optimisation, Sum over all tracks associated to SV (Class 1 (best) jets for CDF) (Class 3 (worst) jets for CDF) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  19. Combination of taggers • Form ratio, where xi is discriminant SV Charge Tagger Electron/Muon Tag d > 0 Intial flavor b d < 0 Initial flavor b Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  20. Same Side Tagging Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  21. Same Side Tagging at CDF • Fragmentation properties are species(Bd or Bs) dependant. • Use Monte Carlo and ensure data-simulation match • Find good agreement. Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  22. Same Side Tagging at CDF • Exploit PID system (TOF + de/dx in drift chamber) for selecting fragmentation kaon. • Select particle with largest kaon probability in vicinity of Bs. Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  23. Same side Tagging (MC Studies) • Studies using Bs  Ds p MC : • Main limitation is kaon Id. • No effect of oscillation • no limiting Branching fraction. • Obtain eD2 ~ 4.0 % Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  24. Bd Mixing & Tagger Calibration Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  25. Bd mixing &Tagger calibration • B+ and Bd decays. Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  26. Tagger Calibration at D0 • Binned asymmetry fit : Bin D mass distribution in 7 Visible Proper decay length VPDL bins(K xM = ctB ,K = PT (D+m)/PTB(gen)): • PDF for oscillated and non-oscillated events: • K-factor (Only in semileptonic B decays) • (Visible) proper decay length resolution VPDL resolution Rec. efficiency of jth channel K-factor Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  27. Bd mixing and tagger calibration • Number of events in VPDL bin i : • Include contribution from cc events. Use VPDL distribution for cc events, s ~150 mm • Allow fcc to float in fit. Fraction from j’th decay mode (sample composition) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  28. For final fit, bin the tag variable |d| in 5 bins and do a simultaneuos fit Asymmetry fits in dilution bins Tagger Calibration at DØ • Dm = 0.506 0.020 (stat.)  0.016 (syst.)ps-1 • eD2 = (2.48  0.210.07) (%) • = (19.9 0.2) (%) fcc= 2.20.9(%) Event-by-event dilution Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  29. Tagger calibration at CDF • Unbinned likelihood fit for Bd mixing for semileptonic and fully hadronic decays to obtain dilution scale factors (developed using inclusive l+SVT sample) • Fit for a global scale factor • Simultaneous fit to mass and lifetime. Ldt = 1 fb-1 Ldt = 355 pb-1 Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  30. Flavor Tag Summary at Tevatron • For comparison of break up, older CDF tagger results quoted.Very recent numbers eD2 (OST) = 1.8% (With Neural network combination of taggers) . For individual tagggers (D0) |d| > 0.3 (Overall is higher). CDF DØ Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  31. Bd Mixing Measurements • Dmd Measurement : D0 New Result: Submitted to Phys. Rev. D. (hep-ex/0609034, Fermilab-PUB-06/341-E) Dmd: 0.506  0.020 (stat.)  0.016(syst.) eD2 (OST) 2.48  0.22 (stat.+syst.) CDF New Result (Apr 2006) Dmd : 0.509  0.010 (stat.)  0.016(syst.) eD2 (OST) 1.50  0.06 (stat.+syst.) CDF very new Result (Sep 2006) eD2 (OST) 1.80  0.01 (stat. only) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  32. Conclusions • Good flavor tagging capabilities in both experiments. DØ exploits its excellent muon coverage while CDF utilizes its particle ID in TOF and de/dx in the tracking chamber. More improvements possible and are being studied. • Both experiments have performed Bd mixing measurements as a check of their flavor tagging calibration. • Dmd (semlep.) = 0.506 0.020 (stat.)0.016(syst.) ps-1 (DØ) • Dmd (semlep.) = 0.509 0.010 (stat.)0.016(syst.) ps-1 (CDF) • Dmd (hadron.) = 0.536 0.028 (stat.)0.006(syst.) ps-1 (CDF) • Using their flavor tagging capabilities DØ established upper bounds on Bs mixing followed by a 3s measurement by CDF and most recently (1 week back!) a >5s measurement ! 17 <Dms < 21 ps-1 @ 90 % C.L. (DØ) Δms =  17.31+0.33-0.18(stat) ± 0.07(syst.) (CDF) Δms =  17.77  0.10(stat) ± 0.07(syst.) (CDF) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  33. THANK YOU, Neville, Sue and Oxford folks..Goodbye Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  34. Performance at Tevatron and B-factories • A few numbers … • e+e- experiments perform about an order of magnitude better. Why? • Oscillations of neutral B mesons introduces dilution (12 %) • Busy environment at hadron colliders, hard to identify inclusive OS. Situation worse in forward (longitudinally boosted) • At B factories, emphasis on particle ID, and ability to utilise full coverage. Hadron collider : Production flavor of OS flavor and SS B correlated e+e- @ Y(4S) : decay flavor of OS and “production” flavor of SS correlated Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  35. BackUp Slides Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  36. CDF Trigger CDF Trigger details: Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  37. Tagger calibration at D0 • eD2 = (1.48  0.17) (%) (stat.) • = (6.6 0.1) (%) (stat.) • eD2 = (0.210.07) (%) (stat.) • = (1.830.07) (%) (stat.) • eD2 = (0.500.11) (%) (stat.) • = (2.77 0.08) (%) (stat.) Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  38. d Same side tagging • Exploit charge correlation between produced B meson and associated particles produced in hadronization process. • Idea given in 1992 by Gronau et. al. • Two sources of same-side tags : • B**- B0 p- • Charge of the “leading” pion/kaon in the fragmentation chain tags the Bd/Bs • SST is characterised by high efficiency but poorer dilution. b B0 b d p- u u p- d B** B0 d b Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

  39. (bu) B0 B0 P.V. D0 Lepton Tagging B+ p+ P.V. Mixing : Wrong sign Tags Sequential decays : Wrong sign Tag e-, m- e-,m- • In the ideal case, b and b are produced in pairs and are oppositely charged and hence the other B meson decay can tag or give the charge of the reconstructed B meson. • bl Xlow branching fraction (~10%) • low efficiency,high dilution (lepton Id). • In the real scenario, we get Wrong sign tags from : • Sequential decays (bce) , Mixing, Fakes. Flavor Tagging at Tevatron, incl. Calibration and Control, T. Moulik.

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