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QCD Meeting June 25, 2004 Is it due to the hard collision? Is it due to fragmentation? Strong polarization seen in fixed-target experiments where jet NOT.

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Presentation on theme: "QCD Meeting June 25, 2004 Is it due to the hard collision? Is it due to fragmentation? Strong polarization seen in fixed-target experiments where jet NOT."— Presentation transcript:

1 QCD Meeting June 25, 2004 Is it due to the hard collision? Is it due to fragmentation? Strong polarization seen in fixed-target experiments where jet NOT observed.  Polarization Tom Devlin Rutgers/CDF _

2 First pass through analysis revealed some problems: 1. Cannot reverse B-Field to cancel biases as was done in fixed-target experiments. 2. Some events have two solutions for decay vertex. 3. Some events have good solutions for both  and K s. There is no remedy for Item 1. There is some hope in comparison of  and . During the past year I have re-written and debugged the code to address Items 2 and 3. _

3 Some events have two solutions. Sailors and Cowboys Displacement in z-direction is poorly known, and it sometimes dictates the wrong choice so that CTVMFT returns the poorer solution.

4 I modified CTVMFT to give 2 solutions (~10% of events) and compare them. After cutting ~identical solutions ~5% have 2 solutions, some unphysical.

5 Sailors & Cowboys: Compare

6 Give weights to solutions: P(  2 )*P(Decay) Gives much more consistent decay curve. Problem: mass resolution & side bands. Above data requires mass centered on , 16 MeV wide.

7 Data from two side bands, centered 16 MeV above and below  mass, each 8 MeV wide.

8 There is a cowboy-sailor difference in mass resolution and background.

9 Fit with mass constraints for 3 hypotheses:  p , K s  and  ee

10 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: Data Dashed lines: 20 hybrid MC-events/real-event scaled by 1/20

11 Work in Progress and Planned: Summer-Fall, Mass-constrained fits: 2- , 2-K s, 1-ee. 2. 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. 5.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.


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