Constrained_Z.cc

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//
//
// File: Constrained_Z.cc
// Purpose: Do kinematic fitting for a (Z->ll)+jets event.
// Created: Apr, 2004, sss
//
// CMSSW File      : src/Constrained_Z.cc
// Original Author : Scott Stuart Snyder <snyder@bnl.gov> for D0
// Imported to CMSSW by Haryo Sumowidagdo <Suharyo.Sumowidagdo@cern.ch>
//

#include "TopQuarkAnalysis/TopHitFit/interface/Constrained_Z.h"
#include "TopQuarkAnalysis/TopHitFit/interface/Fourvec_Event.h"
#include "TopQuarkAnalysis/TopHitFit/interface/Lepjets_Event.h"
#include "TopQuarkAnalysis/TopHitFit/interface/Defaults.h"
#include <ostream>
#include <cassert>
#include <cstdio>

namespace hitfit {

  //*************************************************************************
  // Argument handling.
  //

  Constrained_Z_Args::Constrained_Z_Args(const Defaults& defs)
      //
      // Purpose: Constructor.
      //
      // Inputs:
      //   defs -        The Defaults instance from which to initialize.
      //
      : _zmass(defs.get_float("zmass")), _fourvec_constrainer_args(defs) {}

  double Constrained_Z_Args::zmass() const
  //
  // Purpose: Return the zmass parameter.
  //          See the header for documentation.
  //
  {
    return _zmass;
  }

  const Fourvec_Constrainer_Args& Constrained_Z_Args::fourvec_constrainer_args() const
  //
  // Purpose: Return the contained subobject parameters.
  //
  {
    return _fourvec_constrainer_args;
  }

  //*************************************************************************

  Constrained_Z::Constrained_Z(const Constrained_Z_Args& args)
      //
      // Purpose: Constructor.
      //
      // Inputs:
      //   args -        The parameter settings for this instance.
      //
      : _args(args), _constrainer(args.fourvec_constrainer_args()) {
    char buf[256];
    sprintf(buf, "(%d) = %f", lepton_label, _args.zmass());
    _constrainer.add_constraint(buf);
  }

  namespace {

    FE_Obj make_fe_obj(const Lepjets_Event_Lep& obj, double mass, int type)
    //
    // Purpose: Helper to create an object to put into the Fourvec_Event.
    //
    // Inputs:
    //   obj -         The input object.
    //   mass -        The mass to which it should be constrained.
    //   type -        The type to assign it.
    //
    // Returns:
    //   The constructed FE_Obj.
    //
    {
      return FE_Obj(obj.p(), mass, type, obj.p_sigma(), obj.eta_sigma(), obj.phi_sigma(), obj.res().p_res().inverse());
    }

    void do_import(const Lepjets_Event& ev, Fourvec_Event& fe)
    //
    // Purpose: Convert from a Lepjets_Event to a Fourvec_Event.
    //
    // Inputs:
    //   ev -          The input event.
    //
    // Outputs:
    //   fe -          The initialized Fourvec_Event.
    //
    {
      assert(ev.nleps() >= 2);
      fe.add(make_fe_obj(ev.lep(0), 0, lepton_label));
      fe.add(make_fe_obj(ev.lep(1), 0, lepton_label));

      for (std::vector<Lepjets_Event_Jet>::size_type j = 0; j < ev.njets(); j++)
        fe.add(make_fe_obj(ev.jet(j), 0, isr_label));

      Fourvec kt = ev.kt();
      fe.set_kt_error(ev.kt_res().sigma(kt.x()), ev.kt_res().sigma(kt.y()), 0);
      fe.set_x_p(ev.met());
    }

    void do_export(const Fourvec_Event& fe, Lepjets_Event& ev)
    //
    // Purpose: Convert from a Fourvec_Event to a Lepjets_Event.
    //
    // Inputs:
    //   fe -          The input event.
    //   ev -          The original Lepjets_Event.
    //
    // Outputs:
    //   ev -          The updated Lepjets_Event.
    //
    {
      ev.lep(0).p() = fe.obj(0).p;
      ev.lep(1).p() = fe.obj(1).p;

      for (std::vector<Lepjets_Event_Jet>::size_type j = 0, k = 1; j < ev.njets(); j++)
        ev.jet(j).p() = fe.obj(k++).p;

      Fourvec nu;
      ev.met() = nu;
    }

  }  // unnamed namespace

  double Constrained_Z::constrain(Lepjets_Event& ev, Column_Vector& pull)
  //
  // Purpose: Do a constrained fit for EV.
  //          Returns the pull quantities in PULL.
  //          Returns the chisq; this will be < 0 if the fit failed
  //          to converge.
  //
  // Inputs:
  //   ev -          The event we're fitting.
  //
  // Outputs:
  //   ev -          The fitted event.
  //   pull -        Pull quantities for well-measured variables.
  //
  // Returns:
  //   The fit chisq, or < 0 if the fit didn't converge.
  //
  {
    Fourvec_Event fe;
    do_import(ev, fe);
    Column_Vector pully;
    double m, sigm;
    double chisq = _constrainer.constrain(fe, m, sigm, pull, pully);
    do_export(fe, ev);

    return chisq;
  }

  std::ostream& operator<<(std::ostream& s, const Constrained_Z& cz)
  //
  // Purpose: Print the object to S.
  //
  // Inputs:
  //   s -           The stream to which to write.
  //   cz -          The object to write.
  //
  // Returns:
  //   The stream S.
  //
  {
    return s << cz._constrainer;
  }

}  // namespace hitfit