| Re: Reconstruction efficiency of LHE tracking [message #9121 is a reply to message #9098] |
Thu, 30 July 2009 16:05   |
StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino
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first-grade participant |
From: *15-87-r.retail.telecomitalia.it
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Hi,
first of all, I suppose you are using tpc and not stt. Please correct me if youa re using stt macros.
The problem appears probably because you are hitting particles at very back angles. where the detector is nto well performant for tracking (and where we expect very few tracks).
If you see the first plot, starting from 0,0,0, you can see that the code does not reconstruct tracks with theta>155°, due mainly to the detector geometry (non enough points to reconstruct the track).
While in the first plot you see a sharp cut, once you smear the vertex in -10, 10, of course the corresponding emission angle will be different, then the sharp cut becomes smooth aroung 155° (you expect that tracks at -10 cm will suffer the cut at thete a bit lowert than 155, while for tracks at +10mm the acceptance should increase a bit at theta more than 155°, but this are small effect. And the tracking is stuill fine.
In the third polot, first of all the hole is not connected to EMC, becuase emc are not used for tracking. Probably at some particular angle there is some geometry effet from the pipe, and than simply tracks are scattered and not reconstructed properly. However, I am quite surprised that you reconstruct up to 160°, apart from the hole due probably to pipe material (if i remember well int he back aprt is not titanium anymore but steel).
Then, it seems there is nothing so awful in the back tracking, or at least it does nto appear from the plot.
My question is now, do we really expect particles at theta < 150°? These should be quite rare events, isn't it?
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