From 9c423fc086752441033009f925ce0d8aac8c63d9 Mon Sep 17 00:00:00 2001
From: swagata87 <physics.swagata@gmail.com>
Date: Thu, 27 Oct 2022 15:08:59 +0200
Subject: [PATCH] require states to be pos-def

---
 .../src/TsosGaussianStateConversions.cc           | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/TrackingTools/GsfTracking/src/TsosGaussianStateConversions.cc b/TrackingTools/GsfTracking/src/TsosGaussianStateConversions.cc
index d4c6e1b11d244..1692614f23389 100644
--- a/TrackingTools/GsfTracking/src/TsosGaussianStateConversions.cc
+++ b/TrackingTools/GsfTracking/src/TsosGaussianStateConversions.cc
@@ -40,12 +40,15 @@ namespace GaussianStateConversions {
     std::vector<TrajectoryStateOnSurface> components;
     components.reserve(singleStates.size());
     for (auto const& ic : singleStates) {
-      components.emplace_back((*ic).weight(),
-                              LocalTrajectoryParameters((*ic).mean(), pzSign, charged),
-                              LocalTrajectoryError((*ic).covariance()),
-                              surface,
-                              field,
-                              side);
+      //require states to be positive-definite
+      if (double det = 0; (*ic).covariance().Det2(det) && det > 0) {
+        components.emplace_back((*ic).weight(),
+                                LocalTrajectoryParameters((*ic).mean(), pzSign, charged),
+                                LocalTrajectoryError((*ic).covariance()),
+                                surface,
+                                field,
+                                side);
+      }
     }
     return TrajectoryStateOnSurface((BasicTrajectoryState*)new BasicMultiTrajectoryState(components));
   }