From ca58ffa552ae62e2165bb10486d3bdffb3ea6757 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?BiaoZhang=20=28=E5=BC=A0=E5=BD=AA=29?=
 <52267892+zhangbiao-phy@users.noreply.github.com>
Date: Sat, 30 May 2026 20:44:32 +0200
Subject: [PATCH] Enhance deuteron candidate selection parameters

Added configurations for deuteron candidate selection and DCA preselection.
---
 PWGHF/D2H/Tasks/taskCd.cxx | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/PWGHF/D2H/Tasks/taskCd.cxx b/PWGHF/D2H/Tasks/taskCd.cxx
index d4ca3b0fbf6..a7997f5c189 100644
--- a/PWGHF/D2H/Tasks/taskCd.cxx
+++ b/PWGHF/D2H/Tasks/taskCd.cxx
@@ -10,7 +10,7 @@
 // or submit itself to any jurisdiction.
 
 /// \file taskCd.cxx
-/// \brief Cd± → d± K∓ π±  analysis task
+/// \brief cd± → d± K∓ π±  analysis task
 /// \author Biao Zhang <biao.zhang@cern.ch>, Heidelberg Universiity
 
 #include "PWGHF/Core/CentralityEstimation.h"
@@ -175,6 +175,10 @@ struct HfTaskCd {
   Configurable<bool> fillTHn{"fillTHn", false, "fill THn"};
   Configurable<bool> fillCandLiteTree{"fillCandLiteTree", false, "Flag to fill candiates lite tree"};
   Configurable<bool> fillCandFullTree{"fillCandFullTree", false, "Flag to fill candiates full tree"};
+  Configurable<bool> cfgUseTofPidForDeuteron{"cfgUseTofPidForDeuteron", false, "Use TOF PID for deuteron candidates"};
+  Configurable<bool> cfgCutOnDeuteronDcaOrdering{"cfgCutOnDeuteronDcaOrdering", false, "Require deuteron DCA to be smaller than kaon and pion DCAs"};
+  Configurable<float> cfgMinDeuteronDcaPreselection{"cfgMinDeuteronDcaPreselection", 0.004, "Minimum deuteron DCA for preselection (cm)"};
+  Configurable<float> cfgMaxDeuteronTofPidPreselection{"cfgMaxDeuteronTofPidPreselection", 5, "Maximum |nSigma TOF| for deuteron preselection"};
 
   SliceCache cache;
 
@@ -406,6 +410,7 @@ struct HfTaskCd {
         float nSigmaItsDe = 0.f;
         float nSigmaTofDe = 0.f, nSigmaTofKa = 0.f, nSigmaTofPi = 0.f;
 
+        float dcaDeuteron = 0.f, dcaKaon = 0.f, dcaPion = 0.f;
         // int itsNClusterSizeDe = 0;
 
         float tpcSignalsDe = 0.f;
@@ -420,8 +425,8 @@ struct HfTaskCd {
         nSigmaTpcKa = candidate.nSigTpcKa1();
         nSigmaTofKa = candidate.nSigTofKa1();
 
-        const bool selDeKPi = (candidate.isSelCdToDeKPi() >= 1);
-        const bool selPiKDe = (candidate.isSelCdToPiKDe() >= 1);
+        const bool selDeKPi = (candidate.isSelCdToDeKPi() >= selectionFlagCd);
+        const bool selPiKDe = (candidate.isSelCdToPiKDe() >= selectionFlagCd);
 
         auto prong0 = candidate.template prong0_as<TrackType>();
         auto prong1 = candidate.template prong1_as<TrackType>();
@@ -446,6 +451,10 @@ struct HfTaskCd {
           tpcSignalsDe = prong0.tpcSignal();
           tpcSignalsPi = prong2.tpcSignal();
           itsSignalsDe = itsSignal(prong0);
+
+          dcaDeuteron = candidate.impactParameter0();
+          dcaKaon = candidate.impactParameter1();
+          dcaPion = candidate.impactParameter2();
         } else if (selPiKDe) {
           candFlag = -1;
           pSignedDe = prong2.tpcInnerParam() * prong2.sign();
@@ -460,6 +469,10 @@ struct HfTaskCd {
           tpcSignalsDe = prong2.tpcSignal();
           tpcSignalsPi = prong0.tpcSignal();
           itsSignalsDe = itsSignal(prong2);
+
+          dcaDeuteron = candidate.impactParameter2();
+          dcaKaon = candidate.impactParameter1();
+          dcaPion = candidate.impactParameter0();
         }
 
         //  PID QA
@@ -476,6 +489,15 @@ struct HfTaskCd {
         registry.fill(HIST("Data/hNsigmaTPCKaVsP"), prong1.tpcInnerParam() * prong1.sign(), nSigmaTpcKa);
         registry.fill(HIST("Data/hNsigmaTOFKaVsP"), prong1.tpcInnerParam() * prong1.sign(), nSigmaTofKa);
 
+        if (cfgUseTofPidForDeuteron && std::abs(nSigmaTofDe) > cfgMaxDeuteronTofPidPreselection) {
+          continue;
+        }
+        if (std::abs(dcaDeuteron) < cfgMinDeuteronDcaPreselection) {
+          continue;
+        }
+        if (cfgCutOnDeuteronDcaOrdering && (std::abs(dcaDeuteron) > std::abs(dcaKaon) || std::abs(dcaDeuteron) > std::abs(dcaPion))) {
+          continue;
+        }
         if (fillCandLiteTree) {
 
           rowCandCdLite(