PWGHF: add info about K-pi pairs from Lc->pKpi decays, and add direct/reso. decay channel info (#6590)

* Add KPi mass selection for Lc->pKpi.

* Add KPi inv. mass to Lc sparses.

* Fix pion mass in KPi mass calculation.

* Add reso. channel info in LC sparses.

* Add reso. channel info in gen. Lc sparses.

* Add helper function for KPi pair mass.

* Take K*0(892) mass from PhysicsConstants.h in O2.

---------

Co-authored-by: Mattia Faggin <mfaggin@cern.ch>

Author: mfaggin

PWGHF/Core/HfHelper.h

@@ -358,6 +358,18 @@ class HfHelper
     return candidate.m(std::array{o2::constants::physics::MassPiPlus, o2::constants::physics::MassKPlus, o2::constants::physics::MassProton});
   }
 
+  template <typename T>
+  auto invMassKPiPairLcToPKPi(const T& candidate)
+  {
+    return RecoDecay::m(std::array{candidate.pVectorProng1(), candidate.pVectorProng2()}, std::array{o2::constants::physics::MassKPlus, o2::constants::physics::MassPiPlus});
+  }
+
+  template <typename T>
+  auto invMassKPiPairLcToPiKP(const T& candidate)
+  {
+    return RecoDecay::m(std::array{candidate.pVectorProng1(), candidate.pVectorProng0()}, std::array{o2::constants::physics::MassKPlus, o2::constants::physics::MassPiPlus});
+  }
+
   // Ξc± → p± K∓ π±
 
   template <typename T>

PWGHF/Core/SelectorCuts.h

@@ -462,7 +462,7 @@ constexpr double cuts[nBinsPt][nCutVars] = {{0.05, 0.2, 0.1, 1000.0, 0.2, 300.0,
 namespace hf_cuts_lc_to_p_k_pi
 {
 static constexpr int nBinsPt = 10;
-static constexpr int nCutVars = 7;
+static constexpr int nCutVars = 8;
 // default values for the pT bin edges (can be used to configure histogram axis)
 // offset by 1 from the bin numbers in cuts array
 constexpr double binsPt[nBinsPt + 1] = {
@@ -480,16 +480,16 @@ constexpr double binsPt[nBinsPt + 1] = {
 auto vecBinsPt = std::vector<double>{binsPt, binsPt + nBinsPt + 1};
 
 // default values for the cuts
-constexpr double cuts[nBinsPt][nCutVars] = {{0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 0  < pT < 1  */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 1  < pT < 2  */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 2  < pT < 3  */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 3  < pT < 4  */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 4  < pT < 5  */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 5  < pT < 6  */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 6  < pT < 8  */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 8  < pT < 12 */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.},  /* 12 < pT < 24 */
-                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0.}}; /* 24 < pT < 36 */
+constexpr double cuts[nBinsPt][nCutVars] = {{0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 0  < pT < 1  */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 1  < pT < 2  */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 2  < pT < 3  */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 3  < pT < 4  */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 4  < pT < 5  */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 5  < pT < 6  */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 6  < pT < 8  */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 8  < pT < 12 */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.},  /* 12 < pT < 24 */
+                                            {0.400, 0.4, 0.4, 0.4, 0., 0.005, 0., -1.}}; /* 24 < pT < 36 */
 
 // row labels
 static const std::vector<std::string> labelsPt = {
@@ -505,7 +505,7 @@ static const std::vector<std::string> labelsPt = {
   "pT bin 9"};
 
 // column labels
-static const std::vector<std::string> labelsCutVar = {"m", "pT p", "pT K", "pT Pi", "Chi2PCA", "decay length", "cos pointing angle"};
+static const std::vector<std::string> labelsCutVar = {"m", "pT p", "pT K", "pT Pi", "Chi2PCA", "decay length", "cos pointing angle", "mass (Kpi)"};
 } // namespace hf_cuts_lc_to_p_k_pi
 
 namespace hf_cuts_lc_to_k0s_p