From 3ad5ff86eec226f88870e1f9b6817723ad01da20 Mon Sep 17 00:00:00 2001
From: miranov25 <marian.ivanov@cern.cg>
Date: Wed, 15 Jul 2026 07:16:14 +0200
Subject: [PATCH] TPC: add ITS-TPC combined-momentum sampling trigger

Add a third sampling trigger bit for tracks with matched ITS-TPC
combined momentum. The new trigger uses the Tsallis sampling function on
the combined-track pT instead of the TPC-only pT and stores the
corresponding weight as weight_ITSTPC.

This extends the existing trigger mask scheme:
  0x1: minimum-bias sampling
  0x2: Tsallis sampling using TPC-only track pT
  0x4: Tsallis sampling using ITS-TPC combined-track pT

The output condition is updated so tracks selected by the new ITS-TPC
sampling path are written even when they are not selected by the existing
TPC-only or minimum-bias triggers.

Motivation:
sampling only on TPC-only momentum can bias correlated observables such
as qpt_TPC - qpt_Comb. The new trigger provides a dedicated sampled
stream for combined-track performance studies while preserving the
existing TPC-only and minimum-bias sampling streams.
---
 Detectors/TPC/workflow/src/TPCTimeSeriesSpec.cxx | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/Detectors/TPC/workflow/src/TPCTimeSeriesSpec.cxx b/Detectors/TPC/workflow/src/TPCTimeSeriesSpec.cxx
index dce9703a6a365..dcb53c9f80ff8 100644
--- a/Detectors/TPC/workflow/src/TPCTimeSeriesSpec.cxx
+++ b/Detectors/TPC/workflow/src/TPCTimeSeriesSpec.cxx
@@ -1335,12 +1335,17 @@ class TPCTimeSeries : public Task
     if (mUnbinnedWriter && mStreamer[iThread]) {
       const float factorPt = mSamplingFactor;
       bool writeData = true;
+      bool writeDataITSTPC = false;
       float weight = 0;
+      float weightITSTPC = 0;
       if (mSampleTsallis) {
         std::uniform_real_distribution<> distr(0., 1.);
         writeData = o2::math_utils::Tsallis::downsampleTsallisCharged(tracksTPC[iTrk].getPt(), factorPt, mSqrt, weight, distr(mGenerator[iThread]));
+        if (hasITSTPC) {
+          writeDataITSTPC = o2::math_utils::Tsallis::downsampleTsallisCharged(tracksITSTPC[idxITSTPC.front()].getPt(), factorPt, mSqrt, weightITSTPC, distr(mGenerator[iThread]));
+        }
       }
-      if (writeData || minBiasOk) {
+      if (writeData || writeDataITSTPC || minBiasOk) {
         auto clusterMask = makeClusterBitMask(trackFull);
         const auto& trkOrig = tracksTPC[iTrk];
         const bool isNearestVtx = (idxITSTPC.back() == -1); // is nearest vertex in case no vertex was found
@@ -1395,7 +1400,11 @@ class TPCTimeSeries : public Task
             }
           }
         }
-        const int triggerMask = 0x1 * minBiasOk + 0x2 * writeData;
+        // triggerMask bits:
+        // 0x1: flat minimum-bias stream
+        // 0x2: Tsallis stream sampled with TPC-only pT
+        // 0x4: Tsallis stream sampled with ITS-TPC combined pT
+        const int triggerMask = 0x1 * minBiasOk + 0x2 * writeData + 0x4 * writeDataITSTPC;
 
         float deltaP2ConstrVtx = -999;
         float deltaP3ConstrVtx = -999;
@@ -1446,6 +1455,7 @@ class TPCTimeSeries : public Task
                             << "factorMinBias=" << factorMinBias
                             << "factorPt=" << factorPt
                             << "weight=" << weight
+                            << "weight_ITSTPC=" << weightITSTPC
                             << "dcar_tpc_vertex=" << dcaTPCAtVertex
                             << "dcar_tpc=" << dca[0]
                             << "dcaz_tpc=" << dca[1]