qcd meeting october 1, 2004
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QCD MeetingOctober 1, 2004
Is it due to the hard collision?
Is it due tofragmentation?
Strong polarization seenin fixed-target experimentswhere jet NOT observed.
PolarizationTom Devlin
Rutgers/CDF
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Status and Plans
Three known contributions to dataset: -- Signal -- Ks Background -- Continuum 2-track background
MC code exists to generate first two.Coding in progress for the third.
Plan: Generate 20 MC of each type for each real event. Mix three MC samples, in appropriate proportions to produce 20 MC events for each real event. Adjust proportions of each and assumed polarization of MC ’s to fit data.
Old Distribution Shown Last TimeFit with no Mass Constraint: Assume Daughters are p
Subtract signal, Smooth Remainder (5-bins)
Fits Without and With Mass Constraints Shown Last Time
Two Major Improvements In This
Eliminate Decay Vertices Within 8 cm of Primary Interaction
Eliminate e+e- Cut Events with M2(ee)<0.01
Signal-Noise Improved By Large Factor
Huge Improvement in Signal/NoiseExtended Momentum Range
from 2-12 GeV/c to 2-20 GeV/cStudy , Ks, Background vs.
Momentum and Flight Distance Lxy
For one bin in p and Lxy: (loose-cut ) – (tight-cut ),(tight-cut Ks), plot both vs. M2(p)
Sum of two plots = Ks + backgroundSubtract from loose-cut Number of pure
Do this for all bins, and for Ks to get Relative Number of , Ks and Background
For Each Bin in Momentum and Lxy Evaluate Fractions of , Ks and
Restrictions on Angular Distribution
Work in Progress and Planned: Fall, 2004
11 Mass-constrained fits: 2-, 2-Ks, 1-ee.11 Sum of weights over solutions = 1.0 per event.11 Use 2 = 2(MassConstraint) - 2(NoMassConstraint)11 Determine relative proportions of , Ks and background5. Modify 2nd stage analysis code to mix MC samples from , Ks, in correct proportions. Possibly as fit parameters with constraints.6. See if a believable polarization analysis can be done in one of the three coordinate systems.7. If so, do polarization in the other two coordinate systems.
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