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_.  Polarization Tom Devlin Rutgers/CDF. Strong polarization seen in fixed-target experiments where jet NOT observed. Is it due to the hard collision?. Is it due to fragmentation?. QCD Meeting October 1, 2004. Status and Plans. Three known contributions to dataset:

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_

 Polarization

Tom Devlin

Rutgers/CDF

Strong polarization seen

in fixed-target experiments

where jet NOT observed.

Is it due to the

hard collision?

Is it due to

fragmentation?

QCD Meeting

October 1, 2004


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 Time

Fit with no Mass Constraint: Assume Daughters are p

Subtract  signal, Smooth Remainder (5-bins)




Eliminate e+e- Cut Events with M2(ee)<0.01



Huge Improvement in Signal/Noise

Extended Momentum Range

from 2-12 GeV/c to 2-20 GeV/c

Study , 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 + background

Subtract from loose-cut   Number of pure 


Do this for all bins and for k s to get relative number of k s and background
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 



Work in Progress and Planned: Fall, 2004

  •  Mass-constrained fits: 2-, 2-Ks, 1-ee.

  •  Sum of weights over solutions = 1.0 per event.

  •  Use 2 = 2(MassConstraint) - 2(NoMassConstraint)

  • Determine relative proportions of , Ks and background

  • Modify 2nd stage analysis code to mix MC samples from

  • , Ks,  in correct proportions.

  • Possibly as fit parameters with constraints.

  • See if a believable polarization analysis can be done

  • in one of the three coordinate systems.

  • If so, do polarization in the other two coordinate systems.


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