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Very preliminary studies on b-tagging

Very preliminary studies on b-tagging. IReS Strasbourg :. Daniel Bloch Denis Gelé Sébastien Greder Isabelle Ripp-Baudot. Developped tools. An à-la Ariel code (thanks !) Work at roottuple level :. Objects : Tracks : linked to MC-Particle, MC-Vertex

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Very preliminary studies on b-tagging

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  1. Very preliminary studies on b-tagging IReS Strasbourg : Daniel Bloch Denis Gelé Sébastien Greder Isabelle Ripp-Baudot Isabelle Ripp-Baudot IReS Strasbourg

  2. Developped tools An à-la Ariel code (thanks !) Work at roottuple level : Objects : Tracks : linked to MC-Particle, MC-Vertex Vertex : ‘’Tracks, MC-Vertex MC-Particle : ‘’MC-P MC-P : give parents MC-Vertex : linked to Tracks, MC-Particle Quark : ‘’MC-Vertex Muons : MuId (needs SMT) MuTr ( tracking only, no SMT) -> J/ peak observed Jets : (all algo)linked to Tracks, Vertex, Muons Charged Jets : using tracker info(new) Isabelle Ripp-Baudot IReS Strasbourg

  3. J/ Top group filtered data : at least 1 high PT lepton 2 « good »  (std selection, Mu-tracking only) 220000 events p10.13.00a runs 139900 to 142886 (only good ones) (01/dec/2001 -> 07/jan/2002) PT() > 5 GeV/c + - Same sign  Isabelle Ripp-Baudot IReS Strasbourg

  4. Association : 2ary vertex to jet Jet – b tagging Only calo info Use of 2ary vertex tracks 1, Associate vertex to jets or 2, Reconstruct jet with tracks Isabelle Ripp-Baudot IReS Strasbourg

  5. Jet /2ary vertex geometricassociation Cone r2 = 2 + 2 r < 0.3 Calo jet axis JCCA algorithm Sum tracks SKSEL = estim (PB) match the cone ? SKSEL Bad tracking, missed tracks -> wrong PB Enable flight distance <0 due to resolution Isabelle Ripp-Baudot IReS Strasbourg

  6. Jet /2ary vertex association MC sample : 10000 evts p10.08.01 tt incl, W->l  + W->l jet min bias = 0.5 poisson 2ary vertex = SKSEL Jet = JCCA Some results of this association method : similar to Ariel’s results in his D0 note - Only 0.5 % of 2ary vertices associated to more than 1 jet. - About 56 % of reconstructed b jets have 2ary vertices associated. - About 43 % of b partons match with a reconstructed and « b-tagged » jet. (= with at least one 2ary vertex associated) • About 10 % of c partons match also with a reconstructed and « b-tagged » jet. Isabelle Ripp-Baudot IReS Strasbourg - About 1 % of light partons ‘’  ‘’ .

  7. Jet /2ary vertex association Lxy ?? Lxy/ SKSEL SKSEL Vertices associated to b-jets Lxy Pull SKSEL SKRECO Isabelle Ripp-Baudot IReS Strasbourg

  8. Likelihood method :discriminating variables Likelihood method : cf. Pavel Demine (ISN Grenoble) 5 discriminating variables. Based on : charged tracks attached to 2ary vertices, vertices and  matched to jets. Decay length significance : 0 = 1ary vertex 1 = 2ary vertex Isabelle Ripp-Baudot IReS Strasbourg

  9. Likelihood method :discriminating variables Fraction of 2ary vertex charged energy w.r.t. jet :  Ptrk X2vtx = Ejet ch Secondary vertex mass : Mvtx2 = M2ch + P2chT + PchT Isabelle Ripp-Baudot IReS Strasbourg

  10. Likelihood method :discriminating variables PT() w.r.t. jet direction : (P . Pjet)2 PT/jet() = P2 –  P2jet Rapidity w.r.t jet axis : (for each track at2ary vtx) 1 Etr + Ptr//jet Y jet = Log 2 Etr– Ptr//jet Isabelle Ripp-Baudot IReS Strasbourg

  11. Data sample Top group filtered data : at least 1 high PT lepton and :  2 jets (JCCA) : 1 « good » jet with 1 « good » matched 2ary vertex or 1 « good » jet with 1 « good » matched  and : selected 1ary vtx  1.5 mm 45700 events p10.13.00a runs 139900 to 142886 « good » 2ary vertex = SKSEL « good » jet : JCCA algo, JetId std selection « good » muon = std selection nseg=3 (A+BC layers), pT()>6 GeV/c Isabelle Ripp-Baudot IReS Strasbourg

  12. Flight distance MC : tt data b quarks Use of tt MC only to have enough 2ary vertices… MC : tt MC : tt c quarks light quarks Isabelle Ripp-Baudot IReS Strasbourg

  13. Decay Length significance MC : tt data b quarks MC : tt MC : tt c quarks light quarks Isabelle Ripp-Baudot IReS Strasbourg

  14. Rapidity w.r.t. jet axis MC : tt data b quarks Individual tracks from 2ary vertex MC : tt MC : tt c quarks light quarks Isabelle Ripp-Baudot IReS Strasbourg

  15. PT() w.r.t. jet axis MuId (needs SMT) MC tt data b quarks MC tt light quarks MC tt c quarks Isabelle Ripp-Baudot IReS Strasbourg

  16. Charged track jets Preliminary tests of kT algorithm. Sample used : 2000 evts Z->bb, p10.08.01. Algo : (yi-yj)2 + (i- j)2 dij = min (p2Ti,p2Tj) D2 with : y = rapidity D = 1 (not optimized) Tracks used : only those attached to PV and SV pT > 1 GeV/c -3 <  < 3 Isabelle Ripp-Baudot IReS Strasbourg

  17. Direction correlation Calo jet  leading jet   Opposite jet Tracks jet Isabelle Ripp-Baudot IReS Strasbourg

  18. Flavour correlation Which parton matches (distance 0.3 with jet axis) with the leading jet ? (distance dr2 = d2 + d2) (1=d, 2=u, 3=s, 4=c, 5=b, 21=g) Track jets Track jets Calo jets Calo jets Distance Flavour Isabelle Ripp-Baudot IReS Strasbourg

  19. Efficiency vs pT PT jet > 5 GeV/c Track jets Calo jets pT(parton) pT(parton) Isabelle Ripp-Baudot IReS Strasbourg

  20. Efficiency vs  Track jets Calo jets (parton) (parton) Isabelle Ripp-Baudot IReS Strasbourg

  21. Outlook Cross checks with some of Ariel’s results : OK. Study on likelihood method is going on. Near future : probability functions of btag variables and fit (at roottuple level). Jets with tracks : very preliminary don’t look so promising at first look -> why ? optimization ?? Isabelle Ripp-Baudot IReS Strasbourg

  22. Flight distance in the data with all SKRECO associated to JCCA jets (same selection than previous) Isabelle Ripp-Baudot IReS Strasbourg

  23. Fraction of charged E (2ary vtx) MC : tt data b quarks MC : tt MC : tt c quarks light quarks Isabelle Ripp-Baudot IReS Strasbourg

  24. Secondary vertex mass MC : tt data b quarks MC : tt MC : tt light quarks c quarks Isabelle Ripp-Baudot IReS Strasbourg

  25. Jet selection 0.05 < EM fraction < 0.95 CH fraction < 0.4 N90 > 1 HotF < 10 Isabelle Ripp-Baudot IReS Strasbourg

  26. PT() w.r.t. jet axis MuTr (without SMT) MC tt data b quarks MC tt MC tt light quarks c quarks Isabelle Ripp-Baudot IReS Strasbourg

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