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Measuring the bb cross-section using B  D o X m - n decays

Measuring the bb cross-section using B  D o X m - n decays. Liming Zhang & Sheldon Stone Syracuse University. MC Efficiency from signal MC 2010. Geometrical cut efficiency is ~17 %. Reconstructable efficiency from MC. Pion from D 0 MuX. Long track requirements >=3 hits in Velo

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Measuring the bb cross-section using B  D o X m - n decays

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  1. Measuring the bb cross-section using BDo X m-n decays Liming Zhang & Sheldon Stone Syracuse University

  2. MC Efficiency from signal MC2010 Geometrical cut efficiency is ~17% Group Meeting May 20, 2010

  3. Reconstructable efficiency from MC Pion from D0MuX Long track requirements >=3 hits in Velo >=3 hits in TT >=3 hits in OT Total inefficiency No enough hits in T stations but in Velo No enough hits in Velo but in T stations No enough hits in both Velo & T stations Muon from D0MuX Overall long track reconstructable efficiency Kaon 66.3% Pion 70.5% Muon 84.9% Group Meeting May 20, 2010

  4. Selection criteria • Common cuts • K & p PT>300 MeV, Sum PT>1400 MeV • K and p IPCHI2>9 • K DLL(K-p)>4, p DLL(p-K)> -10 • all tracks fit c2/NDOF<10 • D0 vertex fit c2<6 • D0 Flight Distance c2>64 • DfB (D from B) Cuts only • m PT > 500 MeV & IPCHI2>4 • m ISMUON and DLL(m-p)>0 • B vertex fit c2<5 • vz(D0) – vz(B) > -0.5mm (loosen) • B DIRA>0.998 • B invariant mass in [3, 5] GeV • Prompt Do cuts only • D0 DIRA > 0.9999 • D0 IPCHI2 < 0.1 mm Has checked by prompt D0 Will be checked by XLp Group Meeting May 20, 2010

  5. The End

  6. Things to do (I) • DoK3p do the same analysis as DoKp: two usages: • Tracking efficiency test using prompt Do(It’s better to use the same cut on the K and one p as used in DoKpand do not cut on the other two p, if background is not large). • adding statistics to DomnX if background is acceptable. Group Meeting May 20, 2010

  7. Outline • MC distributions from prompt D0 and DfB • Efficiency ratio of prompt D0 and DfB • MC distributions from signal MC • Efficiency from signal MC All distributions are obtained without any selections. Group Meeting May 20, 2010

  8. IP & IPS from D0 daughters p IP significance K IP significance Prompt D0 DfB K IP p IP Group Meeting May 20, 2010

  9. P & Pt from D0 daughters Prompt D0 DfB Group Meeting May 20, 2010

  10. Distributions of D0 D0 Flight Distance Significance Prompt D0 DfB D0 vertex c2 D0 Pt Sum Pt Group Meeting May 20, 2010

  11. MC Efficiency for D0 (Inc_D0 MC 2010) Efficiency DfB/Prompt = 2.8 ± 0.1 Relative efficiency with respect to the previous cut Geometrical cut efficiency is (42.5 ± 0.2)% Group Meeting May 20, 2010

  12. MC Efficiency from signal MC2010 (cont’) Group Meeting May 20, 2010

  13. Distributions of B B vertex c2 DIRA M(D0m) vz(D0)-vz(B) MC are sum of B+ and B0 Group Meeting May 20, 2010

  14. Things to do • Evaluate cut efficiency from prompt D0 • Especially for IPCHI2 and FDCHI2 cuts • One idea is to smear the resolution and check. • Fake muon background estimation • Remove muon ID • Reweight candidates by the fake rate obtained from the data. Group Meeting May 20, 2010

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