New DOCA and IP functors for T-Tracks

This MR introduces three new functors dedicated primarily to T-Tracks, NONLINEAR_DOCA, NONLINEAR_POCA, and GSIP, for estimation of the distance of closest approach and the corresponding point, as well as an impact parameter, respectively.

All the functors rely on an LHCb::Trajectory interface, which is now working correctly for T-Tracks because of the improvements proposed in LHCb!5276 (merged) !4572 (merged). In the case of NONLINEAR_DOCA, the result is computed using the TrajPoca algorithm, while for GSIP it's a Golden-Section minimisation proposed in LHCb!5276 (merged).

MC distributions of the new variables

Presentations

• "New T-track functors" [WP3 meeting; September 30].

References

• [1] "Physics with T-tracks using 2024 data"; General Performance Meeting; Apr. 28
• [2] "FarTreeFitter: a dedicated framework for fitting decay chains inside the magnet region"; RTA-DPA general meeting; May 2

FYI: @femartin @isanders

Depends on LHCb!5276 (merged). Goes with Moore!5196 (merged) !4572 (merged).