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Fact: The multi-generational structure of the quark doublets requires explanation and could herald compositeness. Motivation. CDF: PRL 82 (1999) 2038. Under hypothesis of compositeness, deviation from point-like behavior would likely manifest in third generation.
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Fact: The multi-generational structure of the quark doublets requires explanation and could herald compositeness. Motivation CDF: PRL 82 (1999) 2038 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 Fit to CDF qQCD calculation
eT Trigger Eff ePV Primary Vertex Eff ej Jet Eff emm Eff fbm Frac b m(Pt > 4 GeV) fBm Frac B m(Pt > 4 GeV) L Luminosity Dpt Pt bin width sb b cross-section sB BKD cross-section m-tagged Jet 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
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.
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
p14 All Data: CSG Skims Bad runs & lumblk removed in luminosity. Only bad run removed in event counts for skims. Up until Run 193780 (07-JUN), V12.37.
Trigger Turn On • Jet Trigger • Collinear muon • |yjet| < 0.5 • Luminosity weighted • Statistics uncorrelated poisson • (wrong, of course) • JES corrected (5.3)
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?
Closer Look Suspicious JT45_TT Pt(m) 4.5-5.0 4.0-4.5 Pt(m)
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
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:
JES v5.3 STD JES 5.3 gives a 3.8% offset for m-tagged jets. It is independent of Pt (75-250 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%.
Extraction of Correction Factors “normal” exponential
Point by Point Unsmearing Factors “normal” Exponential Unsmearing Error small ~5% for Pt > 100 GeV
PtRel at High Pt PtRel muon jet
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.
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.