13 – 17 April

I continue with the project started last week: a class to calculate the probability ratio. While getting this, I port some other functions into the class that were used with the ROOT interpreter before. My progress is quite good, so on Wednesday I’m able to finish this and have a ratio value for each particle combination.

On Thursday, I stay at home to write and stand by in case I need to drive to Bochum. The next day I’m back in Jülich to start with the next big task on the list: the distance to a propagated track.

The idea here is, that a combined candidate has to come at some point from the origin. By using the momentum and position information from the reconstruction, one can propagate this particle back to the presumable origin at (0,0,0), the interaction point. This should be done until this track is closest to the interaction point and the distance to this stored. The distance shouldn’t be far off, otherwise the track is probably from a wrong combination.

My first idea is to use momentum and position information to define a helix, which is approximately the path a charged particle takes in a solenoid magnetic field as we have it in PANDA. From this helix it is now possible to calculate the distance to a point and this should be minimizable, at least numerically. I find a paper describing exactly this, so I read it to understand the effort needed to implement this.