Rivet analyses

title: LHCB_2015_I1401225

Mass distributions in the decay $D^0\to K^-\pi^+\mu^+\mu^-$

Experiment: LHCB (LHC)

Inspire ID: 1401225

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 757 (2016) 558-567

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0

Kinematic distributions in the decay $D^0\to K^-\pi^+\mu^+\mu^-$. Resolution/acceptance effects have been not unfolded.

Source code:LHCB_2015_I1401225.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief class LHCB_2015_I1401225 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2015_I1401225);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 421);
  declare(ufs, "UFS");
  DecayedParticles D0(ufs);
  D0.addStable(PID::PI0);
  D0.addStable(PID::K0S);
  declare(D0, "D0");
  for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix], 1, 1, 1 + ix);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{321, 1}, {211, 1}, {13, 1}, {-13, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{321, 1}, {-211, 1}, {13, 1}, {-13, 1}};
  DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
  // loop over particles
  for (unsigned int ix = 0; ix < D0.decaying().size(); ++ix) {
    int sign = 1;
    if (D0.decaying()[ix].pid() > 0 && D0.modeMatches(ix, 4, mode)) {
      sign = 1;
    }
    else if (D0.decaying()[ix].pid() < 0 && D0.modeMatches(ix, 4, modeCC)) {
      sign = -1;
    }
    else
      continue;
    const Particle& Kp = D0.decayProducts()[ix].at(-sign * 321)[0];
    const Particle& pim = D0.decayProducts()[ix].at(sign * 211)[0];
    const Particle& mup = D0.decayProducts()[ix].at(13)[0];
    const Particle& mum = D0.decayProducts()[ix].at(-13)[0];
    _h[0]->fill((Kp.momentum() + pim.momentum()).mass() / MeV);
    _h[1]->fill((mum.momentum() + mup.momentum()).mass() / MeV);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 2; ++ix) normalize(_h[ix], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2];
/// @}

};

RIVET_DECLARE_PLUGIN(LHCB_2015_I1401225);

} ```