Rivet analyses

title: LHCB_2023_I2643022

Mass distributions in $B^+\to J/\psi\eta^\prime K^+$

Experiment: LHCB (LHC)

Inspire ID: 2643022

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2303.09443

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+, originally pp

Mass distributions in $B^+\to J/\psi\eta^\prime K^+$. Background subtracted data extracted from figure 2 in the paper.

Source code:LHCB_2023_I2643022.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B+ -> J/psi eta' K+ class LHCB_2023_I2643022 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2023_I2643022);


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

/// Book histograms and initialise projections before the run
void init() {
  // projection
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BP(ufs);
  BP.addStable(PID::ETAPRIME);
  BP.addStable(PID::JPSI);
  declare(BP, "BP");
  // histos
  for (unsigned int ix = 0; ix < 3; ++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}, {331, 1}, {443, 1}};
  static const map<PdgId, unsigned int> modeCC = {{-321, 1}, {331, 1}, {443, 1}};
  DecayedParticles BP = apply<DecayedParticles>(event, "BP");
  // loop over particles
  for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
    int sign = 1;
    if (BP.decaying()[ix].pid() > 0 && BP.modeMatches(ix, 3, mode)) {
      sign = 1;
    }
    else if (BP.decaying()[ix].pid() < 0 && BP.modeMatches(ix, 3, modeCC)) {
      sign = -1;
    }
    else {
      continue;
    }
    const Particle& Kp = BP.decayProducts()[ix].at(sign * 321)[0];
    const Particle& eta = BP.decayProducts()[ix].at(331)[0];
    const Particle& psi = BP.decayProducts()[ix].at(443)[0];
    _h[0]->fill((Kp.mom() + eta.mom()).mass());
    _h[1]->fill((psi.mom() + eta.mom()).mass());
    _h[2]->fill((psi.mom() + Kp.mom()).mass());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h, 1.0, false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[3];
/// @}

};

RIVET_DECLARE_PLUGIN(LHCB_2023_I2643022);

} ```