Rivet analyses

title: LHCB_2024_I2756705

$\pi^+\pi^0$ mass distribution in $B_c^+\to J/\psi \pi^+\pi^0$ decays

Experiment: LHCB (LHC)

Inspire ID: 2756705

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - JHEP 04 (2024) 151 - arXiv: 2402.05523

Beams: * *

Beam energies: ANY

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

Mass distributions in $B_c^+$ decays to $J/\psi \pi^+\pi^0$. The background subtracted data were extracted from figure 5 in the paper.

Source code:LHCB_2024_I2756705.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B_c -> J/psi pi+pi0 class LHCB_2024_I2756705 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2024_I2756705);

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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 541);
  declare(ufs, "UFS");
  DecayedParticles BC(ufs);
  BC.addStable(PID::PI0);
  BC.addStable(PID::JPSI);
  declare(BC, "BC");
  book(_h, 1, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{443, 1}, {211, 1}, {111, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{443, 1}, {-211, 1}, {111, 1}};
  DecayedParticles BC = apply<DecayedParticles>(event, "BC");
  // loop over particles
  for (unsigned int ix = 0; ix < BC.decaying().size(); ++ix) {
    int sign = BC.decaying()[ix].pid() / BC.decaying()[ix].abspid();
    if ((sign == 1 && BC.modeMatches(ix, 3, mode)) || (sign == -1 && BC.modeMatches(ix, 3, modeCC))) {
      const Particle& pi0 = BC.decayProducts()[ix].at(111)[0];
      const Particle& pip = BC.decayProducts()[ix].at(sign * 211)[0];
      FourMomentum ptotal = pi0.momentum() + pip.momentum();
      _h->fill(ptotal.mass());
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h, 1., false);
}

/// @}

/// @name Histograms
/// @{
Histo1DPtr _h;
/// @}

};

RIVET_DECLARE_PLUGIN(LHCB_2024_I2756705);

} ```