[PWGHF] Add 3-prong combinatorics with ML-based single-track selection

[fchinu]

This PR adds a simple workflow, similar to the trackIndexSkimCreator (TISC), that runs the combinatorics for Ds and D+ mesons (at the moment only these two are supported) using a ML model to select tracks before the combinatorics.

The ML I used to test this PR is a multiclass BDT which distinguishes background tracks from signal pions/kaons. Two separate models are trained for D+ -> piKpi and Ds -> phi pi -> KKPi.
The idea would be to get a faster and more efficient TISC by pruning the amount of tracks to be processed in the combinatorics. In the TISC, all tracks passing the selections are considered for the combinatorics. Here, I only loop on tracks that satisfy a given hypothesis for a given decay: for example, for the D+, I only loop on tracks passing the BDT selection for 1) D+ pions, 2) D+ kaons and 3) D+ pions again.

Testing on MC (LHC25a5) for central PbPb collisions, this leads to a sizable improvement as compared to the TISC (which was ran enabling only Ds and D+ candidates), both in terms of efficiency:

	generated	TISC matched	TISC eff. (%)	ML matched	ML eff. (%)	ML/TISC
D+ inclusive	7 695	28	0.364	53	0.689	1.89
D+ prompt	4 387	21	0.479	35	0.798	1.67
D+ non-prompt	3 308	7	0.212	18	0.544	2.57
Ds inclusive	3 966	27	0.681	39	0.983	1.44
Ds prompt	1 366	7	0.512	10	0.732	1.43
Ds non-prompt	2 600	20	0.769	29	1.115	1.45

Of number of candidates:

	TISC	ML	ML/TISC
candidates	99 439	71 408	0.72
D+ candidates	69 114	57 002	0.82
Ds candidates	33 200	15 502	0.47
candidates flagged both D+ and Ds	2 875	1 096	0.38

And of CPU:

	TISC	ML	ML/TISC
wall time	5 794 s	1 122 s	0.19
CPU, whole pipeline	7 694 s	3 126 s	0.41

Further tests would be needed before considering using this workflow at analysis level.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 0 warnings, 🔕 2 disabled

[alibuild]

Error while checking build/O2Physics/o2 for 23ad41b at 2026-09-11 14:35:

## sw/BUILD/O2Physics-latest/log
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:460:157: error: arithmetic between enumeration type 'TrackTimingStep' and floating-point type 'float' is deprecated [-Werror=deprecated-enum-float-conversion]
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:840:144: error: arithmetic between enumeration type 'TimingStep' and floating-point type 'float' is deprecated [-Werror=deprecated-enum-float-conversion]
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:846:150: error: arithmetic between enumeration type 'LoopCounter' and floating-point type 'float' is deprecated [-Werror=deprecated-enum-float-conversion]
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/Utils/utilsEvSelHf.h:408:36: error: 'const struct o2::soa::Table<o2::aod::Hash<519320931>, o2::aod::Hash<1837103245>, o2::aod::Hash<519320931>, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<1174303634>, o2::aod::Hash<1219172363>, o2::aod::Hash<2286545062> > >::TableIteratorBase<o2::soa::DefaultIndexPolicy, o2::soa::Join<o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<1174303634>, o2::aod::Hash<1219172363>, o2::aod::Hash<2286545062> > >, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<1174303634>, o2::aod::Hash<1219172363>, o2::aod::Hash<2286545062> > >' has no member named 'isInelGt0'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/Utils/utilsEvSelHf.h:408:36: error: 'const struct o2::soa::Table<o2::aod::Hash<519320931>, o2::aod::Hash<1837103245>, o2::aod::Hash<519320931>, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<2009600272>, o2::aod::Hash<1261423717>, o2::aod::Hash<2286545062> > >::TableIteratorBase<o2::soa::DefaultIndexPolicy, o2::soa::Join<o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<2009600272>, o2::aod::Hash<1261423717>, o2::aod::Hash<2286545062> > >, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<2009600272>, o2::aod::Hash<1261423717>, o2::aod::Hash<2286545062> > >' has no member named 'isInelGt0'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/Utils/utilsEvSelHf.h:408:36: error: 'const struct o2::soa::Table<o2::aod::Hash<519320931>, o2::aod::Hash<1837103245>, o2::aod::Hash<519320931>, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<3914022046>, o2::aod::Hash<1102176623>, o2::aod::Hash<2286545062> > >::TableIteratorBase<o2::soa::DefaultIndexPolicy, o2::soa::Join<o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<3914022046>, o2::aod::Hash<1102176623>, o2::aod::Hash<2286545062> > >, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<3914022046>, o2::aod::Hash<1102176623>, o2::aod::Hash<2286545062> > >' has no member named 'isInelGt0'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/Utils/utilsEvSelHf.h:408:36: error: 'const struct o2::soa::Table<o2::aod::Hash<519320931>, o2::aod::Hash<1837103245>, o2::aod::Hash<519320931>, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<4025989913>, o2::aod::Hash<845892459>, o2::aod::Hash<2286545062> > >::TableIteratorBase<o2::soa::DefaultIndexPolicy, o2::soa::Join<o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<4025989913>, o2::aod::Hash<845892459>, o2::aod::Hash<2286545062> > >, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<4025989913>, o2::aod::Hash<845892459>, o2::aod::Hash<2286545062> > >' has no member named 'isInelGt0'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/Utils/utilsEvSelHf.h:408:36: error: 'const struct o2::soa::Table<o2::aod::Hash<519320931>, o2::aod::Hash<1837103245>, o2::aod::Hash<519320931>, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> > >::TableIteratorBase<o2::soa::DefaultIndexPolicy, o2::soa::Join<o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> > >, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >, o2::soa::Table<o2::aod::Hash<254116537>, o2::aod::Hash<3484684091>, o2::aod::Hash<2286545062> > >' has no member named 'isInelGt0'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGHF/Utils/utilsEvSelHf.h:408:36: error: 'const struct o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> >::TableIteratorBase<o2::soa::DefaultIndexPolicy, o2::soa::Table<o2::aod::Hash<1373761118>, o2::aod::Hash<4191360419>, o2::aod::Hash<2286545062> > >' has no member named 'isInelGt0'
ninja: build stopped: subcommand failed.

Full log here.

[alibuild]

Error while checking build/O2Physics/code-check for c024fc4 at 2026-09-11 15:44:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 3 errors and 22 warnings.'
Found 3 errors and 22 warnings.
++ [[ 3 -gt 0 ]]
++ cat /sw/BUILD/5816e278e75ada6393fc90b680ad55115fde5d92/O2Physics-code-check/errors.txt
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:191:41: error: no header providing "std::distance" is directly included [misc-include-cleaner,-warnings-as-errors]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:398:40: error: no header providing "std::size_t" is directly included [misc-include-cleaner,-warnings-as-errors]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:461:35: error: no header providing "TH1" is directly included [misc-include-cleaner,-warnings-as-errors]
++ [[ 22 -gt 0 ]]
++ cat /sw/BUILD/5816e278e75ada6393fc90b680ad55115fde5d92/O2Physics-code-check/warnings.txt
PWGHF/Core/HfMlResponseHfTracks.h:38:9: warning: function-like macro 'CHECK_AND_FILL_VEC_HF_TRACK' used; consider a 'constexpr' template function [cppcoreguidelines-macro-usage]
PWGHF/Core/HfMlResponseHfTracks.h:138:3: warning: function 'getModelBin' should be marked [[nodiscard]] [modernize-use-nodiscard]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:118:11: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:183:43: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:183:72: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:183:101: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:183:130: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:183:159: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:183:177: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:183:197: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:189:42: warning: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:189:55: warning: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:190:25: warning: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:191:50: warning: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:339:41: warning: initializer for member 'response' is redundant [readability-redundant-member-init]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:423:43: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:423:60: warning: implicit conversion 'bool' -> 'int' [readability-implicit-bool-conversion]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:732:78: warning: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:735:70: warning: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:988:9: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:1103:5: warning: uninitialized record type: 'whichHypo3Prong' [cppcoreguidelines-pro-type-member-init]
PWGHF/D2H/TableProducer/mlBasedTrackSelector.cxx:1252:13: warning: empty catch statements hide issues; to handle exceptions appropriately, consider re-throwing, handling, or avoiding catch altogether [bugprone-empty-catch]
++ [[ 3 -gt 0 ]]
++ exit 1
--

Full log here.