QCD Meeting October 1, 2004 Is it due to the hard collision? Is it due to fragmentation? Strong...

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.