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[Hongwei Ke <kehw AT rcf.rhic.bnl.gov>]

Hi Fleming and all

Thank you for the info. Here is what I have implemented and ready for test.

1. I use bField = 1e-6 Tesla instead of zero to make sure all extrapolation functions work properly. This value is chosen arbitrarily. As long as it is not zero, the math should be correct.
2. To "match FST", I extrapolate TPC tracks to three surfaces.

1. A cylinder: r = 36cm, 148 <= z <= 182cm  # cylinder geometry is easier to deal with 
2. A disk r <= 36, z = 148
3. A disk r <= 36, z = 182
4. These values can be changed easily. If needed, they can be implemented as Run Control parameters that can be turned by shift crew run-by-run.

The track extrapolation is done in sequence. If there is one track hits any of those three surfaces, it is a match and the event will be tagged. From my standalone test on a signal daq file from run 22326045, 748 out of 30374 events are tagged. The ratio is ~2.5%.

Best regards,

Hongwei Ke

On Nov 22, 2021, at 4:05 PM, videbaek <videbaek AT bnl.gov> wrote:

Hi Hongwei,
cc Xu

With the actual positions  the z range should rather be 148 to 182,
As Xu says you can ether use a square for the xy cut or maybe better a circle with radius say 36(40)

F.


On 2021-11-22 15:59, Xu Sun wrote:

Hi Hongwei,
The radius of the FST disk is about 31cm, therefore, I quote 40cm for
both x and y.
Not sure why Carl quotes y = 0, maybe Carl could comment.
Best,
Xu
On Mon, Nov 22, 2021 at 3:57 PM Hongwei Ke <kehw AT rcf.rhic.bnl.gov>
wrote:

Hi Xu,
Carl’s number in his Nov 20 email to star-ops are a little
different.

Would it be possible for L4 to identify those events with a cosmic
track that projects through the rectangle:
-40 < x < +40
140 < z < 180
At y=0

Which one should I use?
Best regards,
Hongwei Ke

On Nov 22, 2021, at 12:28 PM, Xu Sun <sunxuhit AT gmail.com> wrote:
Hi Hongwei,
As discussed in today's 10 clock meeting, please find the FST
position below:
x & y: -40 to 40 cm
z: 140 to 180 cm.
Hope this helps.
Best,
Xu

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Flemming Videbaek
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