TrackerMeasurementFromHits: fix time component of covariance

This value is not used yet, but should be squared, in principle.

src/algorithms/tracking/TrackerMeasurementFromHits.cc

@@ -125,7 +125,7 @@ namespace eicrecon {
             meas2D.setLoc({static_cast<float>(pos[0]),static_cast<float>(pos[1])});                     // 2D location on surface
             meas2D.setTime(hit.getTime());                     // Measurement time
             // fixme: no off-diagonal terms. cov(0,1) = cov(1,0)??
-            meas2D.setCovariance({cov(0,0),cov(1,1),hit.getTimeError(),cov(0,1)}); // Covariance on location and time
+            meas2D.setCovariance({cov(0,0), cov(1,1), hit.getTimeError() * hit.getTimeError(), cov(0,1)}); // Covariance on location and time
             meas2D.addToWeights(1.0);                             // Weight for each of the hits, mirrors hits array
             meas2D.addToHits(hit);
         }