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November 30 th, 2001P. Demine (ISN Grenoble)1 Off-line b-tagging first look at the data Pavel Demine (ISN Grenoble)
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November 30 th, 2001P. Demine (ISN Grenoble)2 b properties –efficient mass m b 4.25 GeV/c 2 –B hadrons have m < 5 GeV/c 2 and 1.56 ps –B decay length c 3mm –particles coming from B have large p T –tracks from B decay are displaced –semi-leptonic decay of B BR (B ) 10%
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November 30 th, 2001P. Demine (ISN Grenoble)3 vtxTagReco impTagReco muTagReco Jets Secondary Vertices eTagReco Tracks Muons Electrons EVENT vtxTags impTags muTags eTags likeTagReco likeTags bIddataflows
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November 30 th, 2001P. Demine (ISN Grenoble)4 First Look at the Data only “good” runs*: –5 416 014 evts processed with p10.07.01 Analysis steps: –Select good JCCA jets (Run II 0.7 cone) –Select good (block MuoTrfit) –Select good displaced vertices (block SKSEL) –Associate selected jets with selected –Associate selected jets with selected vtx –Apply b-tagging cuts over selected objects * for details: www-d0.fnal.gov/computing/production_runs/p10.07.01.pdf
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November 30 th, 2001P. Demine (ISN Grenoble)5 jet selection runnum > 131087 (calorimeter software group) 0.05 < EM fraction < 0.95 CH fraction < 0.4 HotF < 10 ( ratio of hottest and next-to- hottest cell ETs ) n90 > 1 ( number of towers comprizing >90% of jet scalar ET ) p T > 15 GeV/c
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November 30 th, 2001P. Demine (ISN Grenoble)6 jet details jet p T, GeV/c
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November 30 th, 2001P. Demine (ISN Grenoble)7 selection Cuts based on muon local tracks (from F. Deliot J/ presentation) –no trigger requirement –at least 2 A wire hits –at least 3 BC wire hits –at least 1 A scint. hit –at least 1 BC scint. hit – 2 > 0
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November 30 th, 2001P. Demine (ISN Grenoble)8 details p T, GeV/c
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November 30 th, 2001P. Demine (ISN Grenoble)9 displaced vertex selection Cuts based on selected secondary Kalman vertices: –vertex constructed from at least 3 tracks –decay length significance L xy / Lxy > 2.0
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November 30 th, 2001P. Demine (ISN Grenoble)10 selections in numbers Total events processed: 5 416 014 2 017 340 (~37%) events with at least 2 selected jets 46 043 (~0.9%) events with at least 1 selected associated with selected jet 9 439 (~0.17%) events with at least 1 selected vtx associated with selected jet
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November 30 th, 2001P. Demine (ISN Grenoble)11 b-tagging related selection at least 2 selected jets - tag: – R(jet axis – ) < 0.5 –1.0 < P Trel ( w.r.t jet axis) < 2.5 GeV/c (recommended by O.Peters) vtx tag: – R(jet axis – sec vtx) < 0.3 –L xy / Lxy > 2.0
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November 30 th, 2001P. Demine (ISN Grenoble)12 tagging variables p Trel, GeV/c L xy / Lxy
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November 30 th, 2001P. Demine (ISN Grenoble)13 inv. mass reconstruction For each jet tagged with or vtx: –find a jet in opposite direction ( > 2.5) –at least 1 of the jets with | | < 1.1 –E jet1 /E jet2 < 5.0 M(jet-jet), GeV/c 2
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November 30 th, 2001P. Demine (ISN Grenoble)14 Conclusion only b-tagging with is really available still needs more studies displaced vertices reconstruction depends much on CFT tracks they hopefully will be available in the post- shutdown data
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