From c5582998d531ef34500668e033bb6179c6b48244 Mon Sep 17 00:00:00 2001
From: Volker Friese <friese@lxi099.gsi.de>
Date: Wed, 31 Jan 2024 06:04:29 +0100
Subject: [PATCH] First version of V0 trigger algorithm
---
algo/CMakeLists.txt | 2 +
algo/trigger/V0Trigger.cxx | 78 ++++++++++++++++++++++++++++++++++++++
algo/trigger/V0Trigger.h | 73 +++++++++++++++++++++++++++++++++++
3 files changed, 153 insertions(+)
create mode 100644 algo/trigger/V0Trigger.cxx
create mode 100644 algo/trigger/V0Trigger.h
diff --git a/algo/CMakeLists.txt b/algo/CMakeLists.txt
index 378c2d50bb..79552f5987 100644
--- a/algo/CMakeLists.txt
+++ b/algo/CMakeLists.txt
@@ -82,6 +82,7 @@ set(SRCS
evbuild/EventbuildChain.cxx
trigger/DigiTriggerConfig.cxx
trigger/TimeClusterTrigger.cxx
+ trigger/V0Trigger.cxx
evselector/DigiEventSelector.cxx
evselector/DigiEventSelectorConfig.cxx
unpack/CommonUnpacker.cxx
@@ -166,6 +167,7 @@ target_include_directories(Algo
${CMAKE_CURRENT_SOURCE_DIR}/ca
${CMAKE_CURRENT_SOURCE_DIR}/qa/unpack
${CMAKE_CURRENT_SOURCE_DIR}/ca/qa
+ ${CMAKE_CURRENT_SOURCE_DIR}/ca/core/data
${CMAKE_CURRENT_SOURCE_DIR}
${CMAKE_SOURCE_DIR}/core/data/global
)
diff --git a/algo/trigger/V0Trigger.cxx b/algo/trigger/V0Trigger.cxx
new file mode 100644
index 0000000000..1bd3937c8d
--- /dev/null
+++ b/algo/trigger/V0Trigger.cxx
@@ -0,0 +1,78 @@
+/* Copyright (C) 2021 GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt
+ SPDX-License-Identifier: GPL-3.0-only
+ Authors: Volker Friese [committer], Dominik Smith */
+
+#include "V0Trigger.h"
+
+namespace cbm::algo
+{
+
+
+ V0Trigger::Result V0Trigger::operator()(const TrackVector& tracks, const V0TriggerConfig& config) const
+ {
+
+ Result result;
+
+ for (auto trackIter1 = tracks.begin(); trackIter1 != tracks.end(); trackIter1++) {
+ for (auto trackIter2 = trackIter1++; trackIter2 != tracks.end(); trackIter2++) {
+
+ // Check track time difference
+ float time1 = trackIter1->fParFirst.GetTime();
+ float time2 = trackIter2->fParFirst.GetTime();
+ if (time2 < time1) {
+ result.second.errTracksUnsorted++;
+ continue;
+ }
+ result.second.numTrackPairs++;
+ if (time2 - time1 > config.cutTime) break;
+ result.second.numTrackPairsWithinTimeCut++;
+
+ // Check PCA cuts
+ auto pca = CalcPCA(trackIter1->fParFirst, trackIter2->fParFirst);
+ double zVertex = pca.first;
+ double dist = pca.second;
+ if (zVertex > config.cutZ && dist < config.cutDist) {
+ double tVertex = 0.5 * (time1 + time2);
+ result.first.push_back(tVertex);
+ }
+ }
+ }
+
+ return result;
+ };
+
+
+ std::pair<double, double> V0Trigger::CalcPCA(const TrackParam& track1, const TrackParam& track2) const
+ {
+
+ // Start point and direction of first track at z = 0
+ const double ax = track1.GetX() - track1.GetTx() * track1.GetZ();
+ const double ay = track1.GetY() - track1.GetTy() * track1.GetZ();
+ const double ux = track1.GetTx();
+ const double uy = track1.GetTy();
+
+ // Start point and direction of second track at z = 0
+ const double bx = track2.GetX() - track2.GetTx() * track2.GetZ();
+ const double by = track2.GetY() - track2.GetTy() * track2.GetZ();
+ const double vx = track2.GetTx();
+ const double vy = track2.GetTy();
+
+ // Difference vectors
+ const double cx = ax - bx;
+ const double cy = ay - by;
+ const double wx = ux - vx;
+ const double wy = uy - vy;
+
+ // z coordinate at closest approach in the x-y plane
+ const double z = -1. * (cx * wx + cy * wy) / (wx * wx + wy * wy);
+
+ // Distance at closest approach in the x-y plane
+ const double dx = cx + z * wx;
+ const double dy = cy + z * wy;
+ const double dist = sqrt(dx * dx + dy * dy);
+
+ return std::make_pair(z, dist);
+ }
+
+
+} // namespace cbm::algo
diff --git a/algo/trigger/V0Trigger.h b/algo/trigger/V0Trigger.h
new file mode 100644
index 0000000000..67bdd732b8
--- /dev/null
+++ b/algo/trigger/V0Trigger.h
@@ -0,0 +1,73 @@
+/* Copyright (C) 2023 GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt
+ SPDX-License-Identifier: GPL-3.0-only
+ Authors: Volker Friese [committer] */
+
+#pragma once // include this header only once per compilation unit
+
+#include "CaTrack.h"
+#include "CaVector.h"
+
+#include <utility>
+#include <vector>
+
+namespace cbm::algo
+{
+
+ /** @struct V0TriggerConfig
+ ** @brief Configuration (cut values) for the V0Trigger class
+**/
+ struct V0TriggerConfig {
+ double cutTime{}; /// Maximum time difference of tracks
+ double cutZ{}; /// Minimum z position at closest approach
+ double cutDist{}; /// Maximum distance at closest approach
+ };
+
+
+ /** @struct V0TriggerMoniData
+ ** @brief Monitoring information for the algorithm V0Trigger
+ **/
+ struct V0TriggerMoniData {
+ size_t errTracksUnsorted{0};
+ size_t numTrackPairs{0};
+ size_t numTrackPairsWithinTimeCut{0};
+ };
+
+
+ class V0Trigger {
+
+ public:
+ typedef std::pair<std::vector<double>, V0TriggerMoniData> Result;
+ typedef cbm::algo::ca::Track Track;
+ typedef cbm::algo::ca::Vector<cbm::algo::ca::Track> TrackVector;
+ typedef cbm::algo::ca::TrackParamS TrackParam;
+
+ /** @brief Constructor **/
+ V0Trigger() = default;
+
+ /** @brief Execution
+ ** @param dataVec Source data vector
+ ** @param winSize Size of trigger window
+ ** @param minNumData Threshold on number of data within the trigger window
+ ** @param deadTime Minimum time between two triggers
+ ** @return Vector of trigger times and monitoring data
+ **/
+ Result operator()(const TrackVector& tracks, const V0TriggerConfig& config) const;
+
+ /** @brief Info to string **/
+ std::string ToString() const;
+
+
+ private:
+ /** @brief Calculation of closest approach of two tracks (straight lines)
+ ** @param track1 Parameters of first track
+ ** @param track2 Parameters of second track
+ ** @return (z position, distance)
+ **
+ ** The closest approach is defined at the z position where the transverse distance of the tracks (in the x-y plane) is minimal.
+ ** This is not strictly the minimal distance in 3-d space, which is mathematically and computationally more involved.
+ ** It should be a good criterion for the purpose of finding displaced vertices.
+ **/
+ std::pair<double, double> CalcPCA(const TrackParam& track1, const TrackParam& track2) const;
+ };
+
+} // namespace cbm::algo
--
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