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Re: Helix and FairTrackParH [message #9057 is a reply to message #9051] Thu, 23 July 2009 18:15 Go to previous messageGo to previous message
Gianluigi Boca is currently offline  Gianluigi Boca
Messages: 177
Registered: March 2004
first-grade participant
 From: *gsi.de
ok, here is the recipy.
You need to know only the starting point of the track and the starting momentum.
Then :

1) find the centre of the Helix circle in the XY plane by drawing
a segment perpendicular to the 2-dimensional (Px, Py) vector.
Such a segment has direction (-Py, Px). Find the
point on such segment that is a Radius distant from the initial
point of the track. That is the center of the trajectory.
Here there is an ambiguity that depends on the charge of the
track. In other words, you must know the charge of track in
order to decide on which side the center lies.
2) You fi0 is defined by the starting point of your track with
respect to any arbitrary but chosen once for all reference
frame in the XY plane.

If you want you can call me on the phone (+496159711680) for better
explanations.

Gianluigi

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