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 35.7 ± 0.3 Reconstruction 93.8 ± 0.2 Track fit  2 /ndof<10 99.3 ± 0.199.4 ± 0.1 P t >300 MeV for K &  93.5 ± 0.393.1 ± 0.3 IP  2 >9 for K &  83.2 ± 0.482.9 ± 0.4 D 0 FD  2 >64 96.9 ± 0.2 PIDK<10 for  99.3 ± 0.199.4 ± 0.1 PIDK>4 for K95.0 ± 0.395.2 ± 0.3  P t >1400 MeV 99.0 ± 0.198.6 ± 0.2 D 0 vertex  2 <6 95.3 ± 0.395.1 ± 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 > 0.9999 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, 2010 6

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, 2010 7

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 ± 0.240.1 ± 0.9 Track fit  2 /ndof<10 99.4 ± 0.199.5 ± 0.2 P t >300 MeV for K &  93.6 ± 0.293.3 ± 0.7 IP  2 >9 for K &  35.2 ± 0.481.9 ± 1.1 D 0 FD  2 >64 79.6 ± 0.695.1 ± 0.7 PIDK<10 for  99.4 ± 0.199.4 ± 0.3 PIDK>4 for K94.7 ± 0.395.5 ± 0.7  P t >1400 MeV 99.0 ± 0.298.4 ± 0.4 D 0 vertex  2 <6 95.0 ± 0.395.3 ± 0.7 D 0 DIRA>0.9999.9 ± 0.199.6 ± 0.2 Total9.07 ± 0.1425.7 ± 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<10 99.9 ± 0.0  P t >500 MeV 93.2 ± 0.392.9 ± 0.4  IP  2 >4 93.0 ± 0.392.2 ± 0.4 ISMUON89.8 ± 0.489.2 ± 0.5 DLL(  )>0 98.7 ± 0.2 B vertex  2 <5 94.0 ± 0.493.0 ± 0.4 B DIRA >0.99896.4 ± 0.3 z(D0)-z(B)>-0.5mm (loosen) 96.7 ± 0.396.8 ± 0.3 M(D 0  )  [3, 5] GeV 84.4 ± 0.681.6 ± 0.7 Total13.7 ± 0.212.6 ± 0.2 12

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, 2010 14