GSF throws warnings regularly with ODD

[andiwand]

I see the following warning quite often with the GSF and the ODD:

Encountered 47 cases where x/X0 exceeds the range of the Bethe-Heitler-Approximation. The maximum x/X0 encountered was 2.0238. Enable DEBUG output for more information.

To avoid CI failures I had to reduce the number of events we run in test_examples with https://github.com/acts-project/acts/pull/3733.

@benjaminhuth mentioned that we may have to re-parametrize the energy loss polynom or to understand why we encounter such thick material in the ODD.

[andiwand]

https://github.com/acts-project/acts/pull/3739 improves the situation by clamping X/X0 to the valid range of the approximation.

Still open

• [ ] investigate where and why we exceed the valid input range of the approximation
• [ ] define a procedure to train/retrain the approximation
• [ ] retrain the approximation for the ODD if necessary

[AJPfleger]

devmeeting: The problem is not ODD specific and can also be seen in ATHENA on the ITk.

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