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Tracking uncertainties [message #14948] Thu, 11 July 2013 16:07 Go to previous message
Ralf Kliemt is currently offline  Ralf Kliemt
Messages: 507
Registered: May 2007
Location: GSI, Darmstadt
first-grade participant

From: *gsi.de
Hi Lia, Gianluigi and tracking experts.


On the last Panda meeting I talked with Gianluigi about the issue of too low chisquare values in particle fitting. We agreed on the strategy to plot differences to mote-carlo, pull distributions and the uncertainty distributions.

You'll find attached a pdf with such distributions from 10k Psi(3770) -> J/Psi pi+ pi -> e+ e- pi+ pi- events.

First page is the fourmomentum. Here only the energy pulls are a bit wide. Second page has the position variable. Residuals look OK but the pulls are too small.

So I went some steps back and check the first track Parameters.
This is a bit tricky as I need to get the MC truth propagated to the actual region of the first parameter. I did so with Geane and PropagateToPlane. As Plane I use the same plane as it is stored in the reconstructed parameter.

The last row on the second page and the third page show these distributions. However, everything looks aweful.
I guess I made a mistake somewhere.

I put an update to svn and also the macro I use to create these plots. You may use any of your own simulations as it only needs measured charged particles and the mc truth.


Hope to find answers.
Ralf


 
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