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

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 14, 2010

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 B DIRA>0.998 B invariant mass in [3, 5] GeV Group Meeting May 14, 2010 Prompt D o cuts only D 0 DIRA > D 0 IPCHI2 < 25 ~800  b -1 Prompt K -  + Mass

IP & IPS from D 0 daughters Group Meeting May 14, 2010 Prompt D 0 DfB K IP  IP K IP significance  IP significance

P & P t from D 0 daughters Group Meeting May 14, 2010 Prompt D 0 DfB

Distributions of D 0 Group Meeting May 14, 2010 Prompt D 0 DfB Sum P t D 0 vertex  2 D 0 P t D 0 Flight Distance Significance

MC Efficiency for D 0 (Inc_D 0 MC 2010) Group Meeting May 14, 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)%

MC Efficiency from signal MC 2010 Group Meeting May 14, 2010 Efficiency [%] B   D 0 X   B   D 0 X   Reconstruction 36.3 ± ± 0.3 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%

MC Efficiency from signal MC 2010 (cont’) Group Meeting May 14, 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 ± ± 0.2

Distributions of B Group Meeting May 14, 2010 DIRA B vertex  2 M(D 0  ) vz(D 0 )  vz(B) MC are sum of B + and B 0

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 14, 2010

The End

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 14, 2010