Chi
This is a great news and an important lesson. It was clear that Genya in
the last few days has spotted a problem by going to the simplest physics
reaction (ep) elastic and the simplest detector configuration. This
shows that with complex detector like BLAST, basic checks and rechecks
are necessary to ensure that there are no fundamental problems at the
most basic level (like charge counting). And we all should have open
minded when some one like Genya suggests that there is a problem. I am
assuming that this problem was not affecting the physics spin
asymetries, though it was affecting the left and right sectors differently.
Genya: you can take the next 1/2 day off!!
Manouchehr
Chi Zhang wrote:
>Hi,
>
>After Genya showed me the data, I found that there IS a bug in the way
>ntuple is filled. When NC/LADS are fired, qwl/qwr is set to 0, charge
>info from WC tracks are overwritten. This is certainly incorrect behavior.
>Sorry I screw up this one.
>
>I fixed the code in head version and crunched run 9719 in
>~blast/cvs_v3.0/BlastLib2_dev. The problem is gone.
>
>To estimate the damage: for run 9719, please see the table below:
>charge of track left(p>0.1) righ(p>0.1)
> - 4721 3437
> + 25933 15817
> 0 1619 5144
> 5% 21%
>the last line is the number of wrong charge over the sum of three rows
>above.
>
>on left sector, 5% of charged tracks had qwl overwritten to 0, on the
>right, 21% of them were affected. Also, compare e-right to e-left case,
>one also finds 27% difficiency.
>
>I hope this explains the huge difference in tracking efficiency Tancredi
>sees(e-right 50%, e-left 70% compare to pure TOF cuts).
>
>I hope this also explains the missing ed events with electron going
>right but I need to see also.
>
>The bug is fixed in ~blast/cvs_v3.0/BlastLib2, lrn, lrd and
>libBlast.so are recompiled and copied to bin(lib)/lrn_v3.0c (lrd_v3.0c and
>libBlast.so_v3.0c respectively) and then linked to lrn (lrd, libBlast.so).
>
>the run currently going on is 9801, it will be crunched with new code.
>
>Thanks to Genya who spotted this problem.
>
>Chi
>
>
-- ____________________________________________________________________ Manouchehr Farkhondeh manouch@mit.edu Principal Research Scientist Division Head of Physics, Accelerator MIT, Bates Linear Accelerator Center tel (617)253-9298 Middleton, MA 01949 fax (617) 253-9599 ____________________________________________________________________
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