From 605da18cd7f61b8532721767ba7369fccc663942 Mon Sep 17 00:00:00 2001 From: Maximiliano Puccio Date: Wed, 18 Feb 2026 12:26:08 +0100 Subject: [PATCH] [ITS] Protect ultra low pt selections at the tracklet level Checked on Pb-Pb simulation that this does not change the number of reconstructed tracks --- Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx b/Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx index 70f4e3d1d3fc7..29fb4ac4c69b5 100644 --- a/Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx +++ b/Detectors/ITSMFT/ITS/tracking/src/TimeFrame.cxx @@ -344,7 +344,6 @@ void TimeFrame::initialise(const int iteration, const TrackingParameter mMSangles.resize(trkParam.NLayers); mPhiCuts.resize(mClusters.size() - 1, 0.f); - float oneOverR{0.001f * 0.3f * std::abs(mBz) / trkParam.TrackletMinPt}; for (unsigned int iLayer{0}; iLayer < nLayers; ++iLayer) { mMSangles[iLayer] = math_utils::MSangle(0.14f, trkParam.TrackletMinPt, trkParam.LayerxX0[iLayer]); @@ -352,12 +351,14 @@ void TimeFrame::initialise(const int iteration, const TrackingParameter if (iLayer < mClusters.size() - 1) { const float& r1 = trkParam.LayerRadii[iLayer]; const float& r2 = trkParam.LayerRadii[iLayer + 1]; + oneOverR = (0.5 * oneOverR >= 1.f / r2) ? 2.f / r2 - o2::constants::math::Almost0 : oneOverR; const float res1 = o2::gpu::CAMath::Hypot(trkParam.PVres, mPositionResolution[iLayer]); const float res2 = o2::gpu::CAMath::Hypot(trkParam.PVres, mPositionResolution[iLayer + 1]); const float cosTheta1half = o2::gpu::CAMath::Sqrt(1.f - math_utils::Sq(0.5f * r1 * oneOverR)); const float cosTheta2half = o2::gpu::CAMath::Sqrt(1.f - math_utils::Sq(0.5f * r2 * oneOverR)); float x = r2 * cosTheta1half - r1 * cosTheta2half; float delta = o2::gpu::CAMath::Sqrt(1.f / (1.f - 0.25f * math_utils::Sq(x * oneOverR)) * (math_utils::Sq(0.25f * r1 * r2 * math_utils::Sq(oneOverR) / cosTheta2half + cosTheta1half) * math_utils::Sq(res1) + math_utils::Sq(0.25f * r1 * r2 * math_utils::Sq(oneOverR) / cosTheta1half + cosTheta2half) * math_utils::Sq(res2))); + /// the expression std::asin(0.5f * x * oneOverR) is equivalent to std::aCos(0.5f * r1 * oneOverR) - std::acos(0.5 * r2 * oneOverR) mPhiCuts[iLayer] = std::min(o2::gpu::CAMath::ASin(0.5f * x * oneOverR) + 2.f * mMSangles[iLayer] + delta, o2::constants::math::PI * 0.5f); } }