Please apologize that I add my opinion here (don't want to cause
confusion).
To my view there is still a difference between the polar coordinate
systems where theta measures the polar angle with respect to the z axis
and phi measures the azimuthal angle with respect to the x axis, thus
theta ranges [0,180] and phi [0,360]. Shifting phi to [-90,270] is simply
a rotation of the polar coordinate system around the z-axis.
Tong's coordinate system with negative theta's and phi's within
[-90,90] might be symmetric and convenient for visualization
but is not a polar coordinate system in the above sense.
The physics finally should usually given in a conventional polar
coordinate system.
Michael
> Douglas Hasell wrote:
>
> > Hi,
> >
> > Unfortunately I have thought of a plausible reason for using
> > the range [-90,270) for the azimuthal angle which Chris suggested today.
> >
> > Something that we might do rather naively for a given track is
> > determine its azimuthal angle by taking the average of the azimuthal
> > angles for the track segments which make up the track. So if the track
> > segments have azimuthal angles 1, 359, 0 for example, then the average
> > (180) clearly isn't what we want.
> >
> > Hopefully people are clever enough to avoid this sort of error
> > but I can imagine it slipping through on occasion.
> >
> > Not saying I'm convinced we should start changing code yet but
> > maybe....
> >
> > Cheers,
> > Douglas
> >
> > 26-415 M.I.T. Tel: +1 617 258 7199
> > 77 Massachusetts Avenue Fax: +1 617 258 5440
> > Cambridge, MA 02139, USA E-mail: hasell@mit.edu
>
> Hi,
>
> This is exactly why my symetric system is superior to
> others even though it is unconventional (or I reversed the
> definition of theta and phi).
> My theta runs from -Pi to +Pi and phi runs from -Pi/2 to +Pi/2.
> Therefore, negative (positive) theta is left (right) sector, and
> negative (positvie) phi is bottom (top) half of the chamber.
> Just looking at the two angles, you can visualize where the
> track is going^;^.
>
> -T
>
>
>
>
--+-------------------------------------+--------------------------+ | Office: | Home: | |-------------------------------------|--------------------------| | Dr. Michael Kohl | Michael Kohl | | Laboratory for Nuclear Science | 89 Marlborough Street | | MIT-Bates Linear Accelerator Center | Boston, MA 02116 | | Middleton, MA 01949 | U.S.A. | | U.S.A. | | | - - - - - - - - - - - - | - - - - - - - - -| | Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de | | Phone: +1-617-253-9207 | +1-617-859-0879 | | Fax: +1-617-253-9599 | | | http://blast.lns.mit.edu | | +-------------------------------------+--------------------------+
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:29 EST