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URGENT: geane - coordinate system [message #5097]

Thu, 27 September 2007 14:09

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Hi!

The geane coordinate system is different from the panda coordinate system. In geane the beam is going along x: (x,y,z) -> (z,y,-x)

Why is this so? In principle GEANE does not need the information of the beam axis. All relevant information is in the geometry and the field. Both data sets are available in the panda coordinate system. Where are they converted?

Using two different coordinate system creates a mess in the tracking.

Regards, Sebastian.

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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Re: URGENT: geane - coordinate system [message #5098 is a reply to message #5097]

Thu, 27 September 2007 14:56

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Furthermore I am a bit puzzled about TrackParP. Andrea you said this would be (q/p, v,w,v',w').
In the code Mohammad made a comment which says: (v,w,v',w',q/p)

Now what is right? How are the covariances ordered?

Cheers!
Sebastian.

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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Re: URGENT: geane - coordinate system [message #5099 is a reply to message #5098]

Thu, 27 September 2007 15:46

Andrea Fontana
Messages: 32
Registered: May 2007

continuous participant

From: *pv.infn.it

Hi Sebastian,
the reason why the geane system is with beam along x axis
is, as far as I know, historical and we had adopted this
convention to properly call geane. We can perhaps think
of a different approach, but in all our tests it did not seem
necessary so far.
Regarding CbmTrackParP, I think the comment is not correct:
all the calculations in SD are internally done with the
convention (q/p,v',w',v,w). See for instance the calculation
of the covariance matrix in SD, where we write:

...
fDQp = TMath::Sqrt(fabs(fCovMatrix[0]));
fDTV = TMath::Sqrt(fabs(fCovMatrix[5]));
fDTW = TMath::Sqrt(fabs(fCovMatrix[9]));
fDV = TMath::Sqrt(fabs(fCovMatrix[12]));
fDW = TMath::Sqrt(fabs(fCovMatrix[14]));
...

See also our report for the SD definition.
Hope this helps.

Ciao,
Andrea

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Re: URGENT: geane - coordinate system [message #5100 is a reply to message #5098]

Thu, 27 September 2007 15:49

Andrea Fontana
Messages: 32
Registered: May 2007

continuous participant

From: *pv.infn.it

Dear all,

regarding the comments in geane and trackbase, I am working
on them. Some are obsolete and need to be removed.

Andrea

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Re: URGENT: geane - coordinate system [message #5101 is a reply to message #5099]

Thu, 27 September 2007 16:04

Lia Lavezzi
Messages: 291
Registered: May 2007
Location: Torino

first-grade participant

From: *pv.infn.it

Hi Sebastian,
concerning the beam direction and the coordinate difference, the particle direction is along the x axis in the transverse (curvilinear) frame, the so called SC: you can always change the reference system from the SC to the master reference system using the function FromSCToMars in CbmGeaneUtil.
Hope this helps.
Ciao,
Lia.

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Re: URGENT: geane - coordinate system [message #5102 is a reply to message #5101]

Thu, 27 September 2007 16:09

Andrea Fontana
Messages: 32
Registered: May 2007

continuous participant

From: *pv.infn.it

Hi again,
Lia and I just had a brief discussion on this thread and
we believe that in some cases the transformation
(x,y,z) -> (z,y,-x) that we tried at GSI the other day
works correctly, but it is not general. The correct way
to transform is the FromSCToMars suggested by Lia: in this
way the transformation between the two systems is properly
taken into account.

Ciao,
Andrea

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Re: URGENT: geane - coordinate system [message #5103 is a reply to message #5102]

Thu, 27 September 2007 17:17

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Hi!

I will think about the (x,y,z)->(z,y,-x) transformation again. However we do not need (and I do not use) SC (at the moment). Only SD and in this case there is no need to have any one distinguished axis.

My question is: where is the transformation done for the Geometry and the Field?

Anyhow - I am working on GeaneTrackRep to hide all this.

Sebastian.

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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Re: URGENT: geane - coordinate system [message #5104 is a reply to message #5097]

Thu, 27 September 2007 17:32

Andrea Fontana
Messages: 32
Registered: May 2007

continuous participant

From: *pv.infn.it

Hello Sebastian,
we do not understand exactly why a transformation should
be done for the geometry and the field.
In CbmTrackParP the track is defined in the SD system with
a detector plane defined by the user: the track parameters
and the errors are calculated on this plane but the tracking
internally (in ERTRAK) is done always in MARS. So there is
no need to transform geometry and field.
Perhaps we did not understand your question: if our reply
is not satisfactory, can you please add more details to your
question?

Andrea and Lia

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Re: URGENT: geane - coordinate system [message #5105 is a reply to message #5103]

Thu, 27 September 2007 17:38

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Hi!

My question is only this: Are the coordinates of our geometry transformed in geane? Probably not. So why do we have to do the trafo at all? The only reason would be, that we want the SC angles to be meassured with respect to the beam, right?

Sebastian.

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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Re: URGENT: geane - coordinate system [message #5106 is a reply to message #5097]

Thu, 27 September 2007 18:00

Andrea Fontana
Messages: 32
Registered: May 2007

continuous participant

From: *pv.infn.it

Hello,
there is no coordinate transformation: geane tracks in MARS.
The only transformations are in the definition of the track
parameters and in their errors calculation: these can be done
in SC or SD and can be transformed in MARS after the tracking.
At this point MARS for geane is identical to MARS for Panda.

In the first tutorial we shot along x axis, but it was
only to keep things simple: in the second tutorial we shot
isotropically in the Panda (MARS) system, so there is nothing
special about x axis. In SC angles are already defined in
MARS as azimuthal and polar angles. If the track is in SD
you have to calculate them by transforming to SC.

We hope this is clear now.

Ciao,
Andrea and Lia

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Re: URGENT: geane - coordinate system [message #5113 is a reply to message #5106]

Fri, 28 September 2007 11:40

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Hi!

Ok. Very good! Thank you for the clarification. So we do not need to bother with any transformation, because all that is needed is already in TrackParP.

Cool! Sebastian.

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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Re: URGENT: geane - coordinate system [message #5116 is a reply to message #5113]

Fri, 28 September 2007 14:17

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Hi!

I have look into CbmTrackParP and I found the place where the confusion sets in:

TVector3 positionsd = util.FromMARSToSDCoord(TVector3(fX, fY, fZ), forigin, fiver, fjver, fkver);
   fU = positionsd.X(); // CHECK
   fV = positionsd.Y(); // CHECK 
   fW = positionsd.Z(); // CHECK

Since fV and fW are used in the trackrepresentation it is implicetely assumed, that X is along the track. So it has indeed nothing to do with the beam-axis.

In other words:

I would like to have: pos=(1,1,0) mom=(0.1,0,1) in MARS

when being projected onto a plane
o(0,0,0) u(1,0,0) v(0,1,0)

to give
v=1; w=1; v'=0.1; w'=0;

this is currently not the case because of the code shown above.
instead one would get
u=1; v=1; u'=0.1; v'=0;

In principle we should use fU and fV or build in some conversion somewhere.
Still thinking about it....

Cheers! Sebastian.

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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Re: URGENT: geane - coordinate system [message #5117 is a reply to message #5116]

Fri, 28 September 2007 14:23

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Hi!

So understood some more.

The problem is that I interpret my DetPlane different than the geane-convention.

I always think that the detectorplane is spanned by x and y (which could be rotated to u and v).

In Geane v,w (corresponding to y,z) of the plane are assumed to span the plane.

...

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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Re: URGENT: geane - coordinate system [message #5118 is a reply to message #5117]

Fri, 28 September 2007 15:07

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Hi!

Ok. It works. Sorry for the confusion!
There will be demo with the GeaneTrackRep in Action soon.

Cheers and have a nice Weekend! Sebastian

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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Re: URGENT: geane - coordinate system [message #5119 is a reply to message #5118]

Fri, 28 September 2007 16:05

Sebastian Neubert
Messages: 282
Registered: March 2006
Location: Munich

first-grade participant

From: *e18.physik.tu-muenchen.de

Hi!

In recotasks/demo

there is a demo scipt which shows how the GeaneTrackRep and a DemoRecoHit are used to caluclated residuals.

Cheers!
Sebastian.

Sebastian Neubert
Technische Universität München
Department Physik E18
sneubert@e18.physik.tu-muenchen.de
tel: +49-8928912592

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