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:
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 _
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. _
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.
I modified CTVMFT to give 2 solutions (~10% of events) and compare them. After cutting ~identical solutions ~5% have 2 solutions, some unphysical.
Sailors & Cowboys: Compare
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.
Data from two side bands, centered 16 MeV above and below mass, each 8 MeV wide.
There is a cowboy-sailor difference in mass resolution and background.
Fit with mass constraints for 3 hypotheses: p , K s and ee
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
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.