message: use same sine cut in physical track model, employ a bound for the sine after rotation, such that the propagation does not fail even though the sine check seems correct. This basically affects only very low-pt tracks, where resolution is not that critical, and the deterioration is anyhow minor
diff: @@ -34,7 +34,7 @@ GPUd() int AliHLTTPCGMPhysicalTrackModel::PropagateToXBzLight( float x, float B
  float pye = fPy - dx*b; // extrapolated py
  float pxe2 = pt2 - pye*pye;
  - if( fPx<1.e-3f || pxe2<1.e-6f ) return -1; // can not transport to x=x
  + if( fPx<(1.f - HLTCA_MAX_SIN_PHI) || pxe2<(1.f - HLTCA_MAX_SIN_PHI)*(1.f - HLTCA_MAX_SIN_PHI) ) return -1; // can not transport to x=x
  float pxe = AliHLTTPCCAMath::Sqrt( pxe2 ); // extrapolated px
  float pti = 1.f/AliHLTTPCCAMath::Sqrt(pt2);
  @@ -141,6 +141,7 @@ GPUd() int AliHLTTPCGMPhysicalTrackModel::PropagateToXBxByBz( float x,
  // transport in rotated coordinate system to X''=xe:
  + if (t.Px() < (1.f - HLTCA_MAX_SIN_PHI)) t.Px() = 1.f - HLTCA_MAX_SIN_PHI;
  if( t.PropagateToXBzLight( xe, bb, dLp )!=0 ) return -1;
  // rotate coordinate system back to the original R{-1}==R{T}
  @@ -159,6 +160,7 @@ GPUd() int AliHLTTPCGMPhysicalTrackModel::PropagateToXBxByBz( float x,
  // a small (hopefully) additional step to X=x. Perhaps it may be replaced by linear extrapolation.
  float ddLp = 0;
  + if (t.Px() < (1.f - HLTCA_MAX_SIN_PHI)) t.Px() = 1.f - HLTCA_MAX_SIN_PHI;
  if( t.PropagateToXBzLight( x, Bz, ddLp ) !=0 ) return -1;
  dLp+=ddLp;
  