Measuring the bb cross-section using BDo X m-n

decays

Liming Zhang & Sheldon Stone

Syracuse University

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 14, 2010

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 B DIRA>0.998 B invariant mass in [3, 5] GeV

Group Meeting May 14, 2010

Prompt Do cuts only D0 DIRA > 0.9999 D0 IPCHI2 < 25

~800 mb-1

Prompt K-p+ Mass

IP & IPS from D0 daughters

Group Meeting May 14, 2010

Prompt D0

DfB

K IP p IP

K IP significancep IP significance

P & Pt from D0 daughters

Group Meeting May 14, 2010

Prompt D0

DfB

Distributions of D0

Group Meeting May 14, 2010

Prompt D0

DfB

Sum Pt

D0 vertex c2

D0 Pt

D0 Flight Distance Significance

MC Efficiency for D0 (Inc_D0 MC 2010)

Group Meeting May 14, 2010

Efficiency [%] Prompt D0 DfB

Reconstruction 39.4 ± 0.2 40.1 ± 0.9

Track fit c2/ndof<10 99.4 ± 0.1 99.5 ± 0.2

Pt>300 MeV for K & p 93.6 ± 0.2 93.3 ± 0.7

IP c2>9 for K & p 35.2 ± 0.4 81.9 ± 1.1

D0 FD c2>64 79.6 ± 0.6 95.1 ± 0.7

PIDK<10 for p 99.4 ± 0.1 99.4 ± 0.3

PIDK>4 for K 94.7 ± 0.3 95.5 ± 0.7

Pt>1400 MeV 99.0 ± 0.2 98.4 ± 0.4

D0 vertex c2<6 95.0 ± 0.3 95.3 ± 0.7

D0 DIRA>0.99 99.9 ± 0.1 99.6 ± 0.2

Total 9.07 ± 0.14 25.7 ± 0.8

Efficiency DfB/Prompt = 2.8 ± 0.1Relative 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-D0Xm-n B0D0Xm-n

Reconstruction 36.3 ± 0.3 35.7 ± 0.3

Track fit c2/ndof<10 99.3 ± 0.1 99.4 ± 0.1

Pt>300 MeV for K & p 93.5 ± 0.3 93.1 ± 0.3

IP c2>9 for K & p 83.2 ± 0.4 82.9 ± 0.4

D0 FD c2>64 96.9 ± 0.2 96.9 ± 0.2

PIDK<10 for p 99.3 ± 0.1 99.4 ± 0.1

PIDK>4 for K 95.0 ± 0.3 95.2 ± 0.3

Pt>1400 MeV 99.0 ± 0.1 98.6 ± 0.2

D0 vertex c2<6 95.3 ± 0.3 95.1 ± 0.3

Geometrical cut efficiency is ~17%

MC Efficiency from signal MC 2010 (cont’)

Group Meeting May 14, 2010

Efficiency [%] B-D0Xm-n B0D0Xm-n

m track fit c2/ndof<10 99.9 ± 0.0 99.9 ± 0.0

m Pt>500 MeV 93.2 ± 0.3 92.9 ± 0.4

m IP c2>4 93.0 ± 0.3 92.2 ± 0.4

ISMUON 89.8 ± 0.4 89.2 ± 0.5

DLL( -m p)>0 98.7 ± 0.2 98.7 ± 0.2

B vertex c2<5 94.0 ± 0.4 93.0 ± 0.4

B DIRA >0.998 96.4 ± 0.3 96.4 ± 0.3

z(D0)-z(B)>-0.5mm (loosen) 96.7 ± 0.3 96.8 ± 0.3

M(D0m) [3, 5] GeV 84.4 ± 0.6 81.6 ± 0.7

Total 13.7 ± 0.2 12.6 ± 0.2

Distributions of B

Group Meeting May 14, 2010

DIRA B vertex c2

M(D0m)vz(D0)-vz(B)

MC are sum of B+ and B0

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 14, 2010

The End

Things to do (I) DoK3 p do the same analysis as DoK : p 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 DoK p and do not cut on the other two , p if background is not large).

adding statistics to DomnX if background is acceptable.

Group Meeting May 14, 2010