Example pcm qa at builder (#3920)

* Example pcm qa at builder

* Require TPC only

* Please consider the following formatting changes (#187)

* true TPC only ONLY

---------

Co-authored-by: David Dobrigkeit Chinellato <david.dobrigkeit.chinellato.cern.ch>
Co-authored-by: ALICE Builder <alibuild@users.noreply.github.com>

Author: ddobrigk

PWGLF/TableProducer/lambdakzerobuilder.cxx

@@ -153,6 +153,8 @@ struct lambdakzeroBuilder {
 
   ConfigurableAxis axisX{"axisX", {200, 0, 200}, "X_{IU}"};
   ConfigurableAxis axisRadius{"axisRadius", {500, 0, 50}, "Radius (cm)"};
+  ConfigurableAxis axisDeltaDistanceRadii{"axisDeltaDistanceRadii", {500, -50, 50}, "(cm)"};
+  ConfigurableAxis axisPositionGuess{"axisPositionGuess", {240, 0, 120}, "(cm)"};
 
   int mRunNumber;
   float d_bz;
@@ -290,6 +292,16 @@ struct lambdakzeroBuilder {
       registry.add("h2dTopoVarPosDCAToPV", "h2dTopoVarPosDCAToPV", kTH2D, {axisPtQA, axisTopoVarDCAToPV});
       registry.add("h2dTopoVarNegDCAToPV", "h2dTopoVarNegDCAToPV", kTH2D, {axisPtQA, axisTopoVarDCAToPV});
       registry.add("h2dTopoVarDCAV0ToPV", "h2dTopoVarDCAV0ToPV", kTH2D, {axisPtQA, axisTopoVarDCAV0ToPV});
+
+      // QA for PCM
+      registry.add("h2d_pcm_DeltaDistanceRadii_True", "h2d_pcm_DeltaDistanceRadii_True", kTH2D, {axisPtQA, axisDeltaDistanceRadii});
+      registry.add("h2d_pcm_DeltaDistanceRadii_Bg", "h2d_pcm_DeltaDistanceRadii_Bg", kTH2D, {axisPtQA, axisDeltaDistanceRadii});
+      registry.add("h2d_pcm_PositionGuess_True", "h2d_pcm_PositionGuess_True", kTH2D, {axisPtQA, axisPositionGuess});
+      registry.add("h2d_pcm_PositionGuess_Bg", "h2d_pcm_PositionGuess_Bg", kTH2D, {axisPtQA, axisPositionGuess});
+      registry.add("h2d_pcm_RadiallyOutgoingAtThisRadius1_True", "h2d_pcm_RadiallyOutgoingAtThisRadius1_True", kTH2D, {axisPtQA, axisPositionGuess});
+      registry.add("h2d_pcm_RadiallyOutgoingAtThisRadius2_True", "h2d_pcm_RadiallyOutgoingAtThisRadius2_True", kTH2D, {axisPtQA, axisPositionGuess});
+      registry.add("h2d_pcm_RadiallyOutgoingAtThisRadius1_Bg", "h2d_pcm_RadiallyOutgoingAtThisRadius1_Bg", kTH2D, {axisPtQA, axisPositionGuess});
+      registry.add("h2d_pcm_RadiallyOutgoingAtThisRadius2_Bg", "h2d_pcm_RadiallyOutgoingAtThisRadius2_Bg", kTH2D, {axisPtQA, axisPositionGuess});
     }
 
     mRunNumber = 0;
@@ -672,6 +684,45 @@ struct lambdakzeroBuilder {
       registry.fill(HIST("h2dTopoVarNegDCAToPV"), lPt, v0candidate.negDCAxy);
       registry.fill(HIST("h2dTopoVarDCAV0ToPV"), lPt, dcaV0toPV);
 
+      // -------------------------------------------------------------------------------------
+      // PCM finding tests
+      //
+      // a) delta1 = D - R1 - R2
+      //             D: distance between two track helix centers in xy
+      //             R1, R2: track radii
+
+      o2::math_utils::CircleXYf_t trcCircle1, trcCircle2;
+      float sna, csa;
+      posTrackPar.getCircleParams(d_bz, trcCircle1, sna, csa);
+      negTrackPar.getCircleParams(d_bz, trcCircle2, sna, csa);
+
+      // distance between circle centers (one circle is at origin -> easy)
+      float centerDistance = std::hypot(trcCircle1.xC - trcCircle2.xC, trcCircle1.yC - trcCircle2.yC);
+
+      // b) delta2 = abs(R2/(R1+R2)*rvec1 + R1/(R1+R2)*rvec2)
+      float r1_r = trcCircle1.rC / (trcCircle1.rC + trcCircle2.rC);
+      float r2_r = trcCircle2.rC / (trcCircle1.rC + trcCircle2.rC);
+      float delta2 = std::hypot(r2_r * trcCircle1.xC + r1_r * trcCircle2.xC, r2_r * trcCircle1.yC + r1_r * trcCircle2.yC);
+
+      // c) delta3 = sqrt(D^2-R^2); D: distance origin-center, R: radius
+      float delta3_track1 = TMath::Sqrt(TMath::Power(trcCircle1.xC, 2) + TMath::Power(trcCircle1.yC, 2) - TMath::Power(trcCircle1.rC, 2));
+      float delta3_track2 = TMath::Sqrt(TMath::Power(trcCircle2.xC, 2) + TMath::Power(trcCircle2.yC, 2) - TMath::Power(trcCircle2.rC, 2));
+
+      // let's just use tagged, cause we can
+      if (!posTrack.hasITS() && !posTrack.hasTRD() && !posTrack.hasTOF() && !negTrack.hasITS() && !negTrack.hasTRD() && !negTrack.hasTOF()) {
+        if (V0.isTrueGamma()) {
+          registry.fill(HIST("h2d_pcm_DeltaDistanceRadii_True"), lPt, centerDistance - trcCircle1.rC - trcCircle2.rC);
+          registry.fill(HIST("h2d_pcm_PositionGuess_True"), lPt, delta2);
+          registry.fill(HIST("h2d_pcm_RadiallyOutgoingAtThisRadius1_True"), lPt, delta3_track1);
+          registry.fill(HIST("h2d_pcm_RadiallyOutgoingAtThisRadius2_True"), lPt, delta3_track2);
+        } else {
+          registry.fill(HIST("h2d_pcm_DeltaDistanceRadii_Bg"), lPt, centerDistance - trcCircle1.rC - trcCircle2.rC);
+          registry.fill(HIST("h2d_pcm_PositionGuess_Bg"), lPt, delta2);
+          registry.fill(HIST("h2d_pcm_RadiallyOutgoingAtThisRadius1_Bg"), lPt, delta3_track1);
+          registry.fill(HIST("h2d_pcm_RadiallyOutgoingAtThisRadius2_Bg"), lPt, delta3_track2);
+        }
+      }
+      // -------------------------------------------------------------------------------------
     } // end QA
     return true;
   }