Re: [BLAST_ANAWARE] phi branch point

From: zhangchi (zhangchi@general.lns.mit.edu)
Date: Thu Apr 03 2003 - 12:09:03 EST


>
> pro's of using [-90, 270] convention:
> 1) one less constraint has to be typed in in order to make plots
> "pretty"
> 2) one less line of code has to be typed in in order to perform
> azimuthal averages properly

Please note that this constraint is what you will be typing for a
gazillion times when writing your analysis script. Imagine zooming into
the left sector using a 0-360 convention?

0-360 will not allow us to do some "quick look" thing we v been doing so
far.

> con's of using [-90, 270] convention:
> 1) despite the intuitive feel that all existing code should NOT need
> to be altered for this new convention, all existing code WILL still
> have to be checked; in particular, i can say for SURE that some of
> the monte Carlo code will HAVE to be changed, despite an intuitive
> feel that it shouldn't

I do not see why Monte Carlo must be changed. Geant has been 0-360 all the
time. We or at least I have not had any problem, in generators, monte
carlo or in reconstruction. We never plot from Coda file, we plot from
reconstructed root file.

> 2) this convention does not agree with what the non-BLAST world
> understands readily, and results shown to and received from the
> non-BLAST world will have to be altered

non-BLAST world only knows BLAST has two sectors, left and right. Try
present a plot with three peaks in azimuthal angle to them ?!

> 3) this convention is yet (another) esoteric concept that we would all
> have to carry around, as it goes against the spherical angle ranges
> that we have all known since 10th grade

I also learned from complex analysis, branch cut should be put wherever
convenient. when integrating a function defined from -x1 to +x2, you do it
from -x1 to +x2, not -x1 to 0 plus 0 to +x2, do you?

Chi



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