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Measuring the bb cross- section using B  D o X   decays Liming Zhang & Sheldon Stone Syracuse University.

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Presentation on theme: "Measuring the bb cross- section using B  D o X   decays Liming Zhang & Sheldon Stone Syracuse University."— Presentation transcript:

1 Measuring the bb cross- section using B  D o X   decays Liming Zhang & Sheldon Stone Syracuse University

2 MC Efficiency from signal MC 2010 Group Meeting May 20, 2010 Efficiency [%] B   D 0 X   B   D 0 X   Reconstructable 40.8 ± ± 0.3 Reconstruction 93.8 ± 0.2 Track fit  2 /ndof< ± ± 0.1 P t >300 MeV for K &  93.5 ± ± 0.3 IP  2 >9 for K &  83.2 ± ± 0.4 D 0 FD  2 > ± 0.2 PIDK<10 for  99.3 ± ± 0.1 PIDK>4 for K95.0 ± ± 0.3  P t >1400 MeV 99.0 ± ± 0.2 D 0 vertex  2 < ± ± 0.3 Geometrical cut efficiency is ~17% 2

3 Reconstructable efficiency from MC Group Meeting May 20, 2010 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 Pion from D 0 MuX Muon from D 0 MuX Overall long track reconstructable efficiency Kaon 66.3% Pion 70.5% Muon 84.9% Long track requirements >=3 hits in Velo >=3 hits in TT >=3 hits in OT 3

4 Selection criteria Common cuts K &  PT>300 MeV, Sum PT>1400 MeV K and  IPCHI2>9 K DLL(K-  )>4,  DLL(  -K)> -10 all tracks fit  2 /NDOF<10 D 0 vertex fit  2 <6 D 0 Flight Distance  2 >64 DfB (D from B) Cuts only  PT > 500 MeV & IPCHI2>4  ISMUON and DLL(  -  )>0 B vertex fit  2 <5 vz(D 0 ) – vz(B) > -0.5mm (loosen) B DIRA>0.998 B invariant mass in [3, 5] GeV Group Meeting May 20, 2010 Prompt D o cuts only D 0 DIRA > D 0 IPCHI2 < 0.1 mm 4 Will be checked by  Has checked by prompt D 0

5 The End

6 Things to do (I) D o  K3  do the same analysis as D o  K  two usages:  Tracking efficiency test using prompt D o (It’s better to use the same cut on the K and one  as used in D o  K  and do not cut on the other two  if background is not large).   adding statistics to D o  X if background is acceptable. Group Meeting May 20,

7 Outline MC distributions from prompt D 0 and DfB Efficiency ratio of prompt D 0 and DfB MC distributions from signal MC Efficiency from signal MC All distributions are obtained without any selections. Group Meeting May 20,

8 IP & IPS from D 0 daughters Group Meeting May 20, 2010 Prompt D 0 DfB K IP  IP K IP significance  IP significance 8

9 P & P t from D 0 daughters Group Meeting May 20, 2010 Prompt D 0 DfB 9

10 Distributions of D 0 Group Meeting May 20, 2010 Prompt D 0 DfB Sum P t D 0 vertex  2 D 0 P t D 0 Flight Distance Significance 10

11 MC Efficiency for D 0 (Inc_D 0 MC 2010) Group Meeting May 20, 2010 Efficiency [%] Prompt D 0 DfB Reconstruction 39.4 ± ± 0.9 Track fit  2 /ndof< ± ± 0.2 P t >300 MeV for K &  93.6 ± ± 0.7 IP  2 >9 for K &  35.2 ± ± 1.1 D 0 FD  2 > ± ± 0.7 PIDK<10 for  99.4 ± ± 0.3 PIDK>4 for K94.7 ± ± 0.7  P t >1400 MeV 99.0 ± ± 0.4 D 0 vertex  2 < ± ± 0.7 D 0 DIRA> ± ± 0.2 Total9.07 ± ± 0.8 Efficiency DfB/Prompt = 2.8 ± 0.1 Relative efficiency with respect to the previous cut Geometrical cut efficiency is (42.5 ± 0.2)% 11

12 MC Efficiency from signal MC 2010 (cont’) Group Meeting May 20, 2010 Efficiency [%] B   D 0 X   B   D 0 X    track fit  2 /ndof< ± 0.0  P t >500 MeV 93.2 ± ± 0.4  IP  2 > ± ± 0.4 ISMUON89.8 ± ± 0.5 DLL(  )> ± 0.2 B vertex  2 < ± ± 0.4 B DIRA > ± 0.3 z(D0)-z(B)>-0.5mm (loosen) 96.7 ± ± 0.3 M(D 0  )  [3, 5] GeV 84.4 ± ± 0.7 Total13.7 ± ±

13 Distributions of B Group Meeting May 20, 2010 DIRA B vertex  2 M(D 0  ) vz(D 0 )  vz(B) MC are sum of B + and B 0 13

14 Things to do Evaluate cut efficiency from prompt D 0  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,


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