From 754b9e8669b8c2588c91e3a295ce470bb1aa9895 Mon Sep 17 00:00:00 2001
From: Marco Cattaneo <marco.cattaneo@cern.ch>
Date: Sat, 26 May 2018 08:48:54 +0000
Subject: [PATCH] Merge branch 'wh_addLinearStateZTraj' into '2018-patches'
Added LinearStateZTraj.h to Tr/TrackKernel
See merge request lhcb/Rec!1082
(cherry picked from commit 452f3f354ef6f4d5dec5772c9366c03bf68b4b29)
f3941e82 added LinearStateZTraj.h
---
Tr/TrackKernel/TrackKernel/LinearStateZTraj.h | 82 +++++++++++++++++++
1 file changed, 82 insertions(+)
create mode 100644 Tr/TrackKernel/TrackKernel/LinearStateZTraj.h
diff --git a/Tr/TrackKernel/TrackKernel/LinearStateZTraj.h b/Tr/TrackKernel/TrackKernel/LinearStateZTraj.h
new file mode 100644
index 00000000000..0a83e26204d
--- /dev/null
+++ b/Tr/TrackKernel/TrackKernel/LinearStateZTraj.h
@@ -0,0 +1,82 @@
+#ifndef LINEARSTATEZTRAJ_H
+#define LINEARSTATEZTRAJ_H
+
+#include "TrackKernel/ZTrajectory.h"
+
+
+
+
+namespace LHCb
+{
+ // ==========================================================================
+ /** @class LinearStateZTraj
+ *
+ * ZTrajectory class for a simple line parametrized by a State. The
+ * difference with StateZTraj is that this one cannot account for
+ * bending in a field. However, it does provide a correct covariance
+ * matrix in the call to 'state(z)', which unfortunately doesn't.
+ *
+ * @author Wouter Hulsbergen
+ * @date 2018-05-25
+ */
+ class LinearStateZTraj : public ZTrajectory
+ {
+ private:
+ const LHCb::State m_state ; /// state on which trajectory is based
+ public:
+ /// Constructor from a state
+ LinearStateZTraj( const LHCb::State& state ) : m_state{state} {}
+ /// Clone
+ std::unique_ptr<LHCb::Trajectory> clone() const override final {
+ return std::unique_ptr<LHCb::Trajectory>{new LinearStateZTraj{*this}}; }
+ /// Return the cached state
+ const LHCb::State& state() const { return m_state ; }
+ /// Position at location z
+ Point position( double z ) const override final {
+ return Point{m_state.x() + (z-m_state.z())*m_state.tx(),m_state.y() + (z-m_state.z())*m_state.ty(),1.0} ; }
+ /// First derivative of position to z
+ Vector direction( double /*z*/ ) const override final { return Vector{m_state.tx(),m_state.ty(),1.0} ; }
+ /// Second derivative of position to z
+ Vector curvature( double /*z*/ ) const override final { return Vector{0,0,0} ; }
+ /// Distance in z until the deviation from the linear
+ /// approximation differs from this trajectory by a given tolerance.
+ double distTo1stError( double /*z*/, double /*tolerance*/, int /*pathDirection*/ ) const override final { return 10*Gaudi::Units::km ; }
+ /// Distance in z until the deviation from the quadratic
+ /// approximation differs from this trajectory by a given tolerance.
+ double distTo2ndError( double /*z*/, double /*tolerance*/, int /*pathDirection*/ ) const override final { return 10*Gaudi::Units::km ; }
+ /// Create a parabolic approximation to the trajectory
+ void expansion( double z, Gaudi::XYZPoint& p, Gaudi::XYZVector& dp, Gaudi::XYZVector& ddp ) const override final
+ {
+ p = position(z) ;
+ dp = direction(z) ;
+ ddp = curvature(z) ;
+ }
+ /// Arclength of total trajectory
+ using ZTrajectory::arclength;
+ /// Arclength between 2 z -locations
+ double arclength(double z1, double z2) const override final { return (z2-z1)*direction(z1).R() ; }
+ /// Estimate for expansion parameter 'z' closest to point
+ double muEstimate(const Point& p) const override final { return p.z() ; }
+ /// return a state at position z
+ virtual LHCb::State state( double z ) const override final
+ {
+ LHCb::State rc = m_state ;
+ rc.linearTransportTo( z ) ;
+ return rc ;
+ }
+ /// return a state vector at position z
+ virtual LHCb::StateVector stateVector( double z ) const override final
+ {
+ const double dz = z - m_state.z() ;
+ return LHCb::StateVector{Gaudi::TrackVector{m_state.x()+dz*m_state.tx(),
+ m_state.y()+dz*m_state.ty(),
+ m_state.tx(),m_state.ty(),m_state.qOverP()},z} ;
+ }
+ /// return the set of reference statevectors for this parameterization (if any)
+ virtual std::vector<StateVector> refStateVectors() const override final {
+ return std::vector<StateVector>{StateVector{m_state.stateVector(),m_state.z()}}; }
+ } ;
+}
+
+
+#endif
--
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