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Add z-specific tomography lines to enhance downstream z

Saverio Mariani requested to merge samarian_velotom_z_ranges into master

See description and requirements in https://gitlab.cern.ch/lhcb/opg/-/work_items/53

=== Description below referred to 2023 conditions, when the development started ===

Tomography data being collected at the pit with lines implemented in !1181 (merged) are found to be concentrated in the central VELO region, while the upstream and downstream ones (where deformation is expected to be maximum) are less populated.

To further help with the tomography analysis, this MR implements an algorithm and an additional trigger line allowing a z range for the material interaction seed (defined for events with at least 3 close VELO track pairs far from the beam).

The line is validated by this figure, showing the material interactions (radial distance from the beamline > 20) in passthrough(in blue), with the NMaterialVertexSeedLine (in green, threshold is here set to 3) and the new lines (in red). In the required z_ranges, the green and red curves agree as expected.

Efficiency for the additional lines on the nominal energy, fully VELO open simulation are:

   NMaterialVertexSeed (z_integrated) 1678/871092 evts (58 KHz)
   NMaterialVertexSeed + z in [-550, -125] 231/871092 (8 KHz)
   NMaterialVertexSeed + z in [200, 1100] 1058/871092 (36 KHz)
Edited by Saverio Mariani

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