[Halld-tracking-hw] DC alignment

[Naomi Jarvis]

Hi,

I loaded the alignment manual into docdb at
https://halldweb.jlab.org/DocDB/0037/003739/001/alignment__notes_oct2017.pdf
 there are several other docs from Mike there relating to alignment

& I pasted some comments about it from Alex Barnes below.

Best,

Naomi.

------------------------------- voice of Barnes:
-------------------------------------------------------

Mike had many directories where he worked on alignment. I tried navigating
by `ls -ltr` to see when he last touched directories and assumed those were
the "best".

/raid13/mstaib/Spring2017Alignment
/raid13/mstaib/CDC_FieldOn_WithoutAlignmentConstants
/raid13/mstaib/CDC_FieldOn_WithAlignmentConstants
/raid13/mstaib/ThesisZeroAlign* directories
/raid13/mstaib/Alignment

I think it might be good to look at when the last calibration constants
appeared in the CCDB and then find a directory that was worked on around
that time. That'll be my guess for the last "correct" results. I struggled
to match what I saw in some of these directories. This document only goes
so far.

I think the FDC part went well. It was the next step which got confusing
and didn't have enough documentation. I couldn't figure out what order he
made tweaks. It's this part that becomes more of an art because you have to
decide which things to hold steady and which things to allow to move. It's
always the same process but you just change the config file to hold some
things and free others. This is the part that Mike said takes the longest
to learn.

Reference documents:
Mike recommended to read the book "Data analysis techniques for high-energy
physics" by Rudolf Frühwirth and M. Regler.

https://halldweb.jlab.org/DocDB/0029/002947/001/MStaibCDCUpdateFeb2016.pdf
slide
8
https://halldweb.jlab.org/DocDB/0032/003229/001/MStaibAlignFeb2016Collab.pdf
https://halldweb.jlab.org/DocDB/0030/003029/002/CDCUpdateMay2016.pdf
https://halldweb.jlab.org/DocDB/0033/003310/001/
MStaib16May2017AlignmentUpdate.pdf
https://halldweb.jlab.org/DocDB/0033/003393/001/mstaib_physics_2017.pdf

This is the extent that I know how to do the alignment. Moving forward in
the alignment, Simon needs to bring some variables from deep within the
code to a higher level so that the alignment plugin can access them. This
will allow MilliPede to handle another higher order correction. Curtis sent
a paper to Mike and I about the problem a while ago. If you look at the
invariant mass of the phi as a function of the difference of the kaon
momenta, you'll see a smile. That means that when both kaons have the same
momenta, you are at a minimum mass value for the phi. As one kaon has more
momenta than the other, the mass of the phi shifts towards higher mass. If
you look at a phi invariant mass normally, you'll notice the right side
looks like it spreads a bit more than the left side. That's what this is
from (I believe).
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