1. November 30 th, 2001P. Demine (ISN Grenoble)1 Off-line b-tagging first look at the data Pavel Demine (ISN Grenoble)

2. 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%

3. 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

4. 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

5. 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

6. November 30 th, 2001P. Demine (ISN Grenoble)6 jet details   jet p T, GeV/c

7. 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

8. November 30 th, 2001P. Demine (ISN Grenoble)8  details     p T, GeV/c

9. 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

10. 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

11. 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

12. November 30 th, 2001P. Demine (ISN Grenoble)12 tagging variables  p Trel, GeV/c L xy /  Lxy

13. 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

14. 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