We've discussed how to select tracks from the vertex and at this
point the method is different for the MRS and the FFS.
It's clear if one looks at the fTrackVertex member in the BrGlbTrack
class:
fTrackVertex; // track vertex (intersection with beam line for Mrs)
// intersection with BB plane for Ffs
(the BB plane (for Ffs) has the beam axis as normal vector)
This means that the bbVtx-trackVtx distribution is only gaussian
for MRS at 90 deg and for FFS at 0 deg. At 30 deg the distribution will
be a distorted gaussian. This effect is probably not very big, but I
think we should change it so that the distribution is gaussian and the
method is the same for MRS/FFS.
A way to do this is to define a plane with the bb vertex as origin and
the normal vector parallel with the spectrometer (z-axis of
TPM1/D1). Tracks should be projected to this plane and the track selection
cuts done in the distance from the track intersection to the origin (bb
vertex) of the plane.
This requires a few changes in BrMrsTrackingModule and BrFfsTrackingModule.
I know that Flemming and Djamel discussed this at some point - Flemming do
you have any comments?
Claus
+-------------------------------------------------------------+
| Claus Jørgensen |
| Cand. Scient. Phone : (+45) 33 32 49 49 |
| Cell : (+45) 27 28 49 49 |
| Niels Bohr Institute, Ta-2, Office : (+45) 35 32 53 07 |
| Blegdamsvej 17, DK-2100, E-mail : ekman@nbi.dk |
| University of Copenhagen Home : www.nbi.dk/~ekman/ |
+-------------------------------------------------------------+
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