Cluster error parameterization

• Test optimization on default cluster error mode with scaling
• Best parameters found within bounds:
  • scaleChiY1: 1.7779086962105004
  • scaleChiY2: 0.5157460329068477
  • scaleChiY3:1.343090130640468
  • scaleChiZ1: 1.0739495259708887
  • scaleChiZ2: 0.5274259679551516
  • scaleChiZ3: 1.1181900592137066
• The "improvement": +0.15% efficiency, +0.2% clone-rate, -0.5% fake-rate
• All of them around bound by [0.5,2.0] by the optimization bounds

Reminder (GPUTPCGMPropagator.h)

That means: E.g. strongest change: scaleChiY2 and scaleChZ2 -> even a factor of ~2 does not change the behaviour of the tracking much. Suspected reason: chi2 of 9 for a cluster must be an extreme outlier -> Cluster is far away and probably not track-attached in the first place so cut only takes effect when scaling factor (e.g. scaleChi*) is large