Hi, holding field codes written by Aki are checked into BlastLib2.
please see BlastLib2/HoldField_BiotSavart.{h,cc} and
HoldCoil_BiotSavart.{h,cc}
An interface class TBLHoldField is added to the library,
HoldField_BiotSavart is made to inherit from it. should anyone come up
other models of holding field, one should conform to the interface defined
in TBLHoldField.
TBLMagField is changed so that it adds holding field to computed
BlastField. and the way we handle the field in recon, this is pretty much
the only place to put the holding field.
Blast_Param/blastrc is changed to add a switch MagField.HoldField to
control the on and off of the holding field functions. an file iron.bh is
added to Blast_Param too which is required for HoldCoil_BiotSavart.
There seems to be an slight overhead due to the addition of holdfield. I
added a switch in HoldField_BiotSavart::GetB() such that when X is larger
than 50 cm, it returns 0 field anyway. We should probably reevaluate this
bound later.
Ran on the first couple of event in run 12013. here are a comparison:
event:
p theta phi z
2 0.333 54.333 190.711 -19.747 with holding field
0.333 54.268 190.975 -19.772 without holding field
5 0.292 58.708 3.228 1.527
0.292 58.686 2.880 1.511
14 0.352 56.209 176.377 -5.424
0.351 56.199 175.970 -5.440
slight differences are seen, as Aki predicted, the change is phi is the
largest and close to 1-sigma of our resolution.
For details about the holding field algorithms, please consult Aki, their
creator.
I want to thank Aki for the marvelous codes which are very easy to work
with and took only a half day incorporate into the existing library.
Chi
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