1. Investigation on QCD group
Ye Li
Graduate Student
UW-Madison

2. Inclusive Jet Production using the Midpoint Algorithm
Measurement of inclusive jet cross section
5 different rapidity regions
Up to |Y|=2.1
Based on 1 fb-1 CDF data
Potentially important to new physics such as quark structure (Tevatron ~ m)
Useful to constrain (anti)proton PDF

3. Jet algorithm: Associate clusters of these particles into jets such that the kinematic properties of the jets can be related to the corresponding properties of the energetic partons produced in the hard scattering process.
4 general criteria:
Fully specified
Theoretically well-behaved
Detector Independence
Order Independence

4. Cross Section in the 5 rapidity bins:

5. Ratio to CTEQ6.1M for the 5 rapidity bins

6. Conclusion: Agreed well with the pQCD prediction of the NLO program EKS using CTEQ6.1M parton distribution

7. b-bbar Dijet Production using SVT
Based on about 260 pb-1
Reconstructed using a cone algorithm
Data is selected requiring two displaced tracks at Level 2
cross section is measured in the central region (|Y|< 1.2)

8. Jets are tagged using the 2 dimensional SecVtx algorithm:
the secondary vertex inside the jet is reconstructed and the jet is positively tagged if the distance of the secondary vertex to the primary vertex of the interaction is positive with respect to the jet axis.

9. The main requirements that define the "SVT b-tagged" jet:
Jet tagged by SecVtx algorithm with ET>30 GeV and |Y|<1.2
Jet associated to a SVT track with PT>2 GeV and |d0|>120 μm

10. b-bbar purity for 2 SVT b-tagged jets is quite high:

11. Result:
The differential cross section unfolded to the hadron level is shown in the pictures attached.
The measurement is compared to LO MC and to NLO predictions from
The sample is generated using a minimum quark PT of 10 GeV in |Y|<1.75, CTEQ6.1M PDFs, μR = μF = sqrt(PT 2 + m2), , and Jimmy to simulate multiple parton interactions.

12. The full jet Et range

13. Differential cross section as a function of the leading jet ET

14. Differential cross section as a function of the di-jet invariant mass

15. Differential cross section as a function of the di-jet azymuth distance

16. Thanks!