b Identification for D Æ

1. b Identification for DÆ • Responsibilitiesin the group bcId: • bcJetReco/bcjet/bcJetChunkR.Van Kooten • bcjet_analyzeR.Van Kooten, P.Demine • bc_eTagReco G. Steinbrueck, F.Baudette • bc_muTagReco O.Peters, V.Jain • bc_impTagReco F.Tilthaut, B.Wijngoarden • bc_vtxTagReco A.Schwarzman, M.Narain • bc_likeTagReco P.Demine, A.Lucotte • MC ProductionP.Demine, A.Lucotte P. Demine (ISN Grenoble)

2. Documentation http://www-d0.fnal.gov/~d0upgrad/d0_private/ /software/bid/review_2001.html P. Demine (ISN Grenoble)

3. Primary vertex efficiency Track Reconstruction Track selection -> Ntrk No Ntrk>2 Stop Yes Fit set of Ntrk tracks Find 2max= Max{2(Ntrk)- 2(Ntrk-1)} Ntrk = Nrej Ntrk=Ntrk-1 Nrej=Nrej+1 Yes 2max > max No Save Vertex P. Demine (ISN Grenoble)

4. Secondary vertex Track Reconstruction Tracks selection: - SMT hits number • - pT > 500 MeV/c Track selection -> Ntrk Form 2-track seed No Good seed Yes Fit set of Ntrk tracks Find 2min= Max{2(Ntrk+1)- 2(Ntrk)} Yes Ntrk=Ntrk+1 2min < max No Save Vertex P. Demine (ISN Grenoble)

5. Tagging with vtx: Algorithm • Reconstruct primary vertex. • Reconstruct secondary vertices. • Reconstruct calorimeter jets. • Match secondary vertices to jets. • For each vertex: • Find the closest jet in R • If R < 0.3, the vertex is associated to the jet and removed from the list of vertices. • Go to (a) until no more vertices remain in the list. • Tag jets based on the decay length of the matched vertices. P. Demine (ISN Grenoble)

6. bc_vtxTagreco.rcp // 2: Imp. param, 9: Kalman filter int VertexType = 9 //dR for vertex-jet matching float DeltaR = 0.3 // decay length (r-phi) float DecayLengthRPHI = 2.5 // decay length (z) float DecayLengthZ = 3.0 // decay length significance float DecayLengthSignificance = 0.0 P. Demine (ISN Grenoble)

7. Tag with vtx: Technicalities • Algorithm is implemented in the bc_vtxTagreco package; • Documentation web page: http://www-d0.fnal.gov/~sch/bid.html P. Demine (ISN Grenoble)

8. Jet direction Track direction Decay length vertex dca Tagging with Impact Parameter • Use b-hadron long lifetime without reconstructing secondary vertex (to gain efficiency) • Consider compatibility of “collection of tracks” (jet) with primary vertex • Use decay length significance of tracks: P. Demine (ISN Grenoble)

9. Tagging with dca: Algorithm • Select best primary vertex for each jet • Select tracks: • (Quality of track fit) • Number of track hits (total / SMT) • Track pT • |2D Impact Parameter| • (V0 Rejection) • (Study further cuts) • Calculate PV probability for each track, based on decay length significance distribution • Combine tracks in jet to form discriminant P. Demine (ISN Grenoble)

10. Jet discriminant • Simplest approach: tag jet with a minimum number of tracks that have significance exceeding a certain value • Simple product of probabilities: D = -ln,  = (Pi) …will yield larger values as #tracks increases • Default, independent of #tracks: D = -lnP, P. Demine (ISN Grenoble)

11. Tag with dca: Technicalities • Algorithm is implemented in the bc_impTagreco package; • Documentation web page: http://www-d0.fnal.gov/~dwijngaa/btag/ http://www-d0.fnal.gov/~filthaut/btag/vrev0401.ps P. Demine (ISN Grenoble)

12. Tag with : Algorithm • Reconstruct calorimeter jets. • Take the muon closest to the jet axis direction within a 0.7 cone. • Calculate the PTRel and Pμ / Ejet variables with this muon. • Use cut values to distinguish b jets from background: • 1 GeV/c < PTRel < 5 GeV/c • 0.15 < Pμ / Ejet <0.5 P. Demine (ISN Grenoble)

13. Tag with : Tagging Variables • Currently using: • P / Ejet • Possible other tagging variables: • DCA of muon • PLRel • PTRel significance P. Demine (ISN Grenoble)

14. PTReltagging variable generator level reconstructed jets and muons P. Demine (ISN Grenoble)

15. Pμ / Ejet tagging variable generator level reconstructed jets and muons P. Demine (ISN Grenoble)

16. Tag with  : Technicalities • Algorithm is implemented in the bc_muTagreco package; • Documentation web page: www-d0.fnal.gov/nikhef/muonbtag/analyses/ttbar/ /d0note_btag.doc P. Demine (ISN Grenoble)

17. Tagging b with electrons • Use the electron from the decay of the b quark to tag the b jet • Challenge: Soft electrons inside jets. SEmReco with the road method • Need good tagging variables: pTrel, p(track)/E(electron) P. Demine (ISN Grenoble)

18. Tagging with e: Algorithm • Find all SemParticles > 2 GeV inside the jet (R < 0.7) • Sort according to quality: • 3 EM and PS match, • 2 EM match, • 1 PS match, • 0 no match. • If there is more than one track of the highest quality present, sort in pTrel • Use the highest quality, highest pTrel track to tag the jet. P. Demine (ISN Grenoble)

19. PTrel for Z->bb generator level (except light quarks) reconstructed jets and electrons P. Demine (ISN Grenoble)

20. bc_eTagreco.rcp // pt cut for tracks float Tagtrackptcut = 1.5 //dR for SEMParticle (track) in Jet float drTrackJetCut = 0.7 // minimum ptrel for a tag float Ptrelcut = 0.0 // minimum p(track)/E(jet) float poveECut = 0.0 // 0 no, 1 PS, 2 EM, 3 EM+PS int minSemMatchQual = 2 P. Demine (ISN Grenoble)

21. Tag with e: Technicalities • Algorithm is implemented in the bc_eTagreco package; • Documentation web page: http://www-d0.fnal.gov/~steinbru/d0_private/etag/ /bc_eTagReco.html P. Demine (ISN Grenoble)

22. Likelihood: Algorithm • For every jet in event: • find secondary vertices in jet cone • select the vertex with max(Mvtx); • find muon in jet cone • calculate likelihood using different probability tables for different || - PT regions. P. Demine (ISN Grenoble)

23. Likelihood: Definition if a value is found, otherwise is the probability density function of discriminating variable probability to find discriminating function value Note: in current versionnuds = 1and nc = 0 P. Demine (ISN Grenoble)

24. Discriminating variables • Decay length significance: • Secondary vertex mass: •  momentum transverse to jet direction: P. Demine (ISN Grenoble)

25. Likelihood: Technicalities • Algorithm is implemented in the bc_likeTagreco package; • Probability tables are generated using bcjet_like_db package; • Documentation web page: http://isnwww.in2p3.fr/d0/bcid/doc/liketagreco.html P. Demine (ISN Grenoble)

26. bcjet_analyze: Algorithm • Loop over bcJet objects in event: • fill blocks with information from bcJet related objects: • calorimeter jet; • secondary vertices in jet cone; • electron associated with jet; • muon associated with jet; • reconstructed tracks associated with jet; • reconstructed tracks associated with secondary vertices; • impact parameter tagger; • likelihood tagger. P. Demine (ISN Grenoble)

27. bcjet_analyze: Advantages • bcjet_analyze has • modular structure; • simple interface; • new modules can be added very easily; P. Demine (ISN Grenoble)

28. bcjet_analyze.rcp • What to do ? • booldoEvent = true • booldoJet = true • booldoMuon = true • booldoElec = true • booldoVtxFit = true • booldoVtxRec = true • booldoLikl = true • booldoTrkJet = true • booldoTrkVtx = true • booldoMC = true • booldoImp = true • booldoImpTrk = true • Output file • stringhbk_file = "bcjet.ntpl" • stringnt_manager = "ROOT"// "HBOOK" P. Demine (ISN Grenoble)

29. bcjet_analyze: Documentation • NTuple content description is located at: http://isnwww.in2p3.fr/d0/bcid/bcjetntpl0804.html P. Demine (ISN Grenoble)