Investigation on QCD group Ye Li Graduate Student UW-Madison - - PowerPoint PPT Presentation

Investigation on QCD group

Ye Li Graduate Student UW-Madison

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 ~ 10-19 m)

• Useful to constrain (anti)proton PDF

• 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

• Cross Section in the 5 rapidity bins:

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

• Conclusion: Agreed well with the pQCD

prediction of the NLO program EKS using CTEQ6.1M parton distribution

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)

• 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.

• 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

• b-bbar purity for 2 SVT b-tagged jets is

quite high:

• 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 MC@NLO. – The MC@NLO 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.

• The full jet Et range

• Differential cross section as a function of

the leading jet ET

• Differential cross section as a function of

the di-jet invariant mass

• Differential cross section as a function of

the di-jet azymuth distance

• Thanks!