New Forward tracking algorithm
Closes #108 (closed), #82 (closed), #78 (closed), #70 (closed)
This MR replaces the previous Forward tracking algorithm with a completely refurbished one.
The algorithm is composed of the following steps:
lf_search_initial_windows_t,
lf_triplet_seeding_t,
lf_triplet_keep_best_t,
lf_calculate_parametrization_t,
lf_extend_tracks_x_t,
lf_extend_tracks_uv_t,
lf_quality_filter_length_t,
lf_quality_filter_tWhat follows is a brief description of the algorithm. For more details, see the following presentation TODO.
- lf_search_initial_windows_t: Search windows are defined utilizing UT tracks, according to their estimated qop, for each layer. Windows in X layers are capped to a maximum of 32 hits. UV windows are looser. UT tracks that do not contain enough hits in the windows according to the reconstructibility criteria, are marked and will not be processed.
- lf_triplet_seeding_t: Triplets are seeded from layers in X
{0, 4, 8}and{3, 7, 11}. Hits are traversed such that for every doublet in the extreme layers, a middle hit is found. A maximum ofwindow size * window sizecandidates are kept per triplet of layers. - lf_triplet_keep_best_t: The best triplets are selected, according to their "chi2". Insertion sort is used.
- lf_calculate_parametrization_t: A cubic parametrization of the triplet is calculated, and will be employed in the rest of algorithms.
- lf_extend_tracks_x_t: Triplets are projected to the remaining X layers, and compatible hits are sought. The best according to chi2 from the cubic parametrization is kept, and its chi2 contribution is also saved.
- lf_extend_tracks_uv_t: Tracks are projected to UV stations, compatible hits are sought.
- lf_quality_filter_length_t: Cuts tracks with less than 10 hits.
- lf_quality_filter_t: A Y fit is done. Tracks are cut according to a combination of their X chi2 and Y chi2, and only the best track per UT track is kept.
A comparison of the efficiency of the algorithm with respect to master is shown in the attached plots. Two algorithm configurations are shown, "Nominal" which tracks down to 300 MeV of PT and 1.5 GeV of P, and "Loose" which tracks down to 0 MeV of PT and 3 GeV of P. The following plots are for long tracks from B decays.
Forward_LongFromB_eta25_P_graph_notElectrons.pdf
Forward_LongFromB_eta25_Pt_graph_notElectrons.pdf
Forward_LongFromB_eta25_Eta_graph_notElectrons.pdf
Forward_LongFromB_eta25_Phi_graph_notElectrons.pdf
Similar plots for long tracks from strange decays emphasize the gains for soft physics in particular in the loose configuration.
Forward_LongStrange_eta25_Phi_graph_notElectrons.pdf
Forward_LongStrange_eta25_Pt_graph_notElectrons.pdf