Vector_Resolution.h

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//
// $Id: Vector_Resolution.h,v 1.1 2011/05/26 09:46:53 mseidel Exp $
//
// File: hitfit/Vector_Resolution.h
// Purpose: Calculate resolutions in p, phi, eta.
// Created: Jul, 2000, sss, based on run 1 mass analysis code.
//
// These objects hold three Resolution objects, one each for p, phi, eta.
// In addition, we have a use_et flag; if set, then the p resolution
// is really in pt.
//
// We can initialize these objects from a string; the format is
//
//   <p-res>/<eta-res>/<phi-res>[/et]
//
// where the resolution formats are as given in Resolution.h.
//
// CMSSW File      : interface/Vector_Resolution.h
// Original Author : Scott Stuart Snyder <snyder@bnl.gov> for D0
// Imported to CMSSW by Haryo Sumowidagdo <Suharyo.Sumowidagdo@cern.ch>
//


#ifndef HITFIT_VECTOR_RESOLUTION_H
#define HITFIT_VECTOR_RESOLUTION_H


#include <string>
#include <iosfwd>
#include "TopQuarkAnalysis/TopHitFit/interface/Resolution.h"
#include "TopQuarkAnalysis/TopHitFit/interface/fourvec.h"


namespace hitfit {


class Vector_Resolution
//
// Purpose: Calculate resolutions in p, phi, eta.
//
{
public:
  // Constructor.  Create a vector resolution object with infinite precision
  Vector_Resolution ();

  // Constructor.  Parse a string as described above.
  Vector_Resolution (std::string s);

  // Constructor from individual resolution objects.
  Vector_Resolution (const Resolution& p_res,
                     const Resolution& eta_res,
                     const Resolution& phi_res,
                     bool use_et = false);

  // Get back the individual resolution objects.
  const Resolution& p_res () const;

  const Resolution& eta_res () const;

  const Resolution& phi_res () const;

  // Return the use_et flag.
  bool use_et () const;

  // Calculate resolutions from a 4-momentum.
  double p_sigma   (const Fourvec& v) const;

  double eta_sigma (const Fourvec& v) const;

  double phi_sigma (const Fourvec& v) const;

  // Smear a 4-vector V according to the resolutions.
  // If DO_SMEAR_DIR is false, only smear the total energy.
  void smear (Fourvec& v,
              CLHEP::HepRandomEngine& engine,
              bool do_smear_dir = false) const;

  // Dump this object, for debugging.
  friend std::ostream& operator<< (std::ostream& s,
                                   const Vector_Resolution& r);

private:
  // State for this object.
  Resolution _p_res;

  Resolution _eta_res;

  Resolution _phi_res;

  bool _use_et;

  // Helper.
  void smear_dir (Fourvec& v, CLHEP::HepRandomEngine& engine) const;
};


} // namespace hitfit


#endif // not HITFIT_VECTOR_RESOLUTION_H