[BLAST_ANAWARE] my Pzz

From: Chi Zhang (zhangchi@MIT.EDU)
Date: Mon Jul 05 2004 - 00:32:48 EDT


Hi, all

I checked the data after reading Genya's email when I got back from
the fire work show.

Here is my fitted values for Pzz, and the atatched figure shows the fitted
theory curve with the data.

Take target spin angle at 32 degrees. I have:
from Parallel kinematics data only: 52.3+-2.5%
from Perpendicular Kinematics only: 61.4+-1.5%
from difference from the two kinematics: 56.9+-1/4%

Consider that Genya uses a model that predicts smaller T20, I think my
number is "consistant" with 61.4*1.2=67.2% on his side.

Note that the difference in Pzz fitted from the two kinematics can be
canceled out by playing with spin angle, while the fit from the
"difference" is very INSENSITIVE to spin angle. So 56.9 would be the
number I report.

I am not sure if 57% is still TOO high to be true. But I am much more
willing to believe it than 85%. It would be a very good news if it is in
fact 57%.

However, if you look at the plot, you will see that at Q2>=0.25(Gev/c)^2,
(the 3rd point in all three figures) data point is biased toward VERY
LARGE asymetry which I believe is NOT real. Also please just ignore the
4th point which contains all events passing my cuts with Q2>0.35. In one
of the figure, the 4th point has no error bar which means 0 count is found
in at least one of the spin states.

If Pzz if fitted by integrating all data into ONE bin, we will get a very
large Pzz due to the weird behavior in the 3rd bin. I think this shows the
limitation of the 1-bin method to determine Pzz.

I think the problem of weird Q2 evolution is likely to be in
detector/software. I would like to use this as an opportunity to remind
every body that our resolutions are still at 30MeV, 1deg, 2.5cm level. I
do not think we will be able to move further with "PHYSICS" before we pay
the price to make the dectectors work as we expected.

In the end, I would like to give a short report on Wed analysis meeting,
if there is one, about a program of wire chamber time to distance
calibration I have been prototyping since the beginning of the summer.

Chi




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