1. Motivation
Fact: The multi-generational structure of the quark doublets requires explanation and could herald compositeness.
Under hypothesis of compositeness, deviation from point-like behavior would likely manifest in third generation.
Conclusion: g  bb may exhibit desired deviant behavior.
Explore b quark dijet mass as a possible signature.
Problem
~100:1 QCD:bb
Solutions
m tagging
2nd VTX tagging
Impact parameter
CDF: PRL 82 (1999) 2038
Fit to CDF
qQCD calculation

2. m-tagged Jet Cross-section
eT Trigger Eff
ePV Primary Vertex Eff
ej Jet Eff
em m Eff
fbm Frac b  m (Pt > 4 GeV)
fBm Frac B  m (Pt > 4 GeV)
L Luminosity
Dpt Pt bin width
sb b cross-section
sB BKD cross-section
Correlated
Jet + m (Pt > 5 GeV)
Given the simplicity of the calculation, there are few likely sources of the excess seen in p13. These could conceivably be N
m JES (central value)
Resolution (i.e. smearing)
p13

3. p14 Analysis Summary Inclusive m-tagged jet corrJCCB (0.5 cone jets)
Standard Jet quality cuts, Standard JET Triggers
Jet tagged with MEDIUM muon
(more on this later)
DR(m, jet) < 0.5
|yjet| < 0.5
JES 5.3
Long term goal was b-jet xsec. Difficult due to no data-driven determination of b-fraction.

4. p14 Skimming Start with CSG QCD skim
Turn into TMBTrees (40M events…on disk)
Skim on Trees
Remove bad runs (CAL, MET, SMT, CFT, JET, Muon)
Remove events w/o 2 jets
Use Ariel d0root_ based package
SKIM 1:  1 leading jet has ~ MEDIUM m (P(m) > 4 GeV)
SKIM 2:  1 leading jet has ~ loose SVT

5. p14 All Data: CSG Skims
Bad runs & lumblk removed in luminosity. Only bad run removed in event counts for skims. Up until Run (07-JUN), V12.37.

6. Trigger Turn On Jet Trigger Collinear muon |yjet| < 0.5
Luminosity weighted
Statistics uncorrelated poisson
(wrong, of course)
JES corrected (5.3)

7. f Distribution of MEDIUM m-tagged jets (+ mycuts)
f(jet+m)
These cuts clearly improve the fake m rate.
Some residual fake m’s must persist. How many?
CHF should be higher for punch through jets?

8. Closer Look
Suspicious
JT45_TT
Pt(m)
Pt(m)

9. What is now a muon? Medium muon (as defined by mID group)
At least one scintillator hit in BC.
Pt(central track) > 5 GeV
|Pt(central) – Pt(global)| < 15 GeV
Rejected if
4.25 < f (muon) < 5.15 AND
|h(detector)| < 1.1
m A layer
cal
jet
Fake m from punch-through
In a jet environment is an
issue

10. Efficiency/Fraction Summary
Detail
Value eT
Trigger Eff
1.000
ePV
Primary Vertex Eff
0.84 ± 0.005 em
m Eff [0.37 ± 0.05]
0.41 ± 0.05 ej
Jet Eff
0.99 ± 0.01
fBm
Frac B  m (Pt > 4 GeV)
Pt dependent
fbm
Frac b  m (Pt > 4 GeV)

11. m JES Definitions Required identically 2 jets
Pt(jet 3, uncor) < 8 OR third jet doesn’t pass jet QC
One jet contains muon, the other doesn’t.
| Df | > 2.84
Imbalance variable:
Independent variable:

12. JES v5.3 STD JES 5.3 gives a 3.8% offset for m-tagged jets.
It is independent of Pt ( GeV). Maybe higher above that. Need to rebin and revisit the idea that the muon Pt may be mis-measured.
Same plot when scaling the m-tagged jets by 3.8%.

13. JES v5.3 Energy Resolution (Fixed)

14. Fitting Functions Variable Value Error N 9.56 × 107 1.7 × 106 a 3.195
0.004 b
5.61
0.04
Variable
Value
Error N1
7.62
0.32 k1
16.90
1.26 N2
3.28
0.60 k2
36.33
3.23

15. Extraction of Correction Factors
“normal”
exponential

16. Point by Point Unsmearing Factors
“normal”
Exponential
Unsmearing Error small
~5% for Pt > 100 GeV

17. PtRel at High Pt
PtRel
muon
jet

18. Fitting to HF fraction

19. Systematic Error Breakdown

20. MC Comparison Pythia using standard DØ MC. NLO uses NLO++ (CTEQ6L)
From Pythia, find fraction of jets tagged with muons (HF only).
Multiply NLO cross-section by Pythia muon-fraction.
This is effectively the NLO k factor.

22. Status DØNote and Conference note to EB025
Residual small bug in code (should have only a few percent effect).
JES error must be reduced to use this before setting limits on new physics.