qcd meeting july 23, 2004 is it due to the hard collision? is it due to fragmentation? strong...
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QCD MeetingJuly 23, 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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Asymmetry plots in beam- and beam-K system (ignores jets)Polarization allowed under parity conservation
is in the y-direction (second from top).
Solid lines: DataDashed lines: 20 hybrid MC-events/real-event scaled by 1/20
Fits Without and With Mass Constraints
How Do We Get Polarization From This?
These cos() plots contain:1. The Signal: and 2. Ks Background3. Background from random 2-track crossings.
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Monte Carlo Simulation
and and Ks are straightforward and in place
Now working on random 2-track crossings
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Work in Progress and Planned: Summer-Fall, 2004
11 Mass-constrained fits: 2-, 2-Ks, 1-ee.11 Sum of weights over solutions = 1.0 per event.3. Mix MC events for events with both K and solutions as in the data, weighted by relative P(2)*P(Decay).4. Further study of sailor-cowboy problem.11 Add fits with mass constraints displaced by 20 MeV.6. Background subtraction.7. Decide whether analysis is viable or not.8. If so, do polarization in the other two coordinate systems.
Additional Tasks
11 Use 2 = 2(MassConstraint) - 2(NoMassConstraint)10. Random 2-track crossings.
24 : Fit with mass-constraint – 4 deg. freedom
23 : Fit without mass-constraint – 3 deg. freedomIrrelevant Fluctuations in 2 e.g. deviations
from exact 3-D intersection at vertex tend to cancel.Strong deviations from correct mass DO NOT cancel in 2 .
Repeat for Mass Constraint = M 20 MeV(Note that p threshold is only 38 MeV below M)
Subtract sum of two sidebands from Signal+Background(Sideband normalization used here is from previous graphs.)
Problem:The backgrounds from sidebands populate
the cos plots at different values from real backgrounds.
Alternate Approach:Generate hybrid MC backgrounds
For each real event, generate 20 MC events• at same decay vertex as real event• parent mass from background mass distribution• random angles in CM system• apply standard acceptance cuts• apply tight cuts in 2
Fit with no Mass Constraint: Assume Daughters are pSubtract signal, Smooth Remainder (5-bins)
Normalize Probability Distribution P(M) to Unit Area.Numerically Integrate.
Find values of M(p) at intervals of 0.01 in the integraland form a table of its integral.
Choose a random number R(0:1)Table Lookup and Interpolate to get M(p)
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.
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