Rivet analyses

title: BELLE_2025_I2897384

Mass distributions in $\Lambda_c^+\to p K^0_S \pi^0$ and $p K^-\pi^+$

Experiment: BELLE (KEKB)

Inspire ID: 2897384

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 112 (2025) 1, 012013 - arXiv: 2503.04371

Beams: * *

Beam energies: ANY

Run details: - Any process producing Lambda_c, originally e+e-

Measurement of the mass distributions in the decay $\Lambda_c^+\to p K^0_S \pi^0$ and $p K^-\pi^+$ by BELLE-II. The data were read from the plots in the paper, are corrected for efficiencies and background subtracted. Resolution may not be corrected.

Source code:BELLE_2025_I2897384.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Lambda_c+ -> p K pi class BELLE_2025_I2897384 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2025_I2897384);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 4122);
  declare(ufs, "UFS");
  DecayedParticles LAMBDAC(ufs);
  LAMBDAC.addStable(PID::PI0);
  LAMBDAC.addStable(PID::K0S);
  declare(LAMBDAC, "LAMBDAC");
  // histograms
  for (size_t ix = 0; ix < 6; ++ix) {
    book(_h[ix], 1, 1, 1 + ix);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{PID::PROTON, 1}, {310, 1}, {111, 1}};
  static const map<PdgId, unsigned int>& mode1CC = {{-PID::PROTON, 1}, {310, 1}, {111, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{PID::PROTON, 1}, {-321, 1}, {211, 1}};
  static const map<PdgId, unsigned int>& mode2CC = {{-PID::PROTON, 1}, {321, 1}, {-211, 1}};
  DecayedParticles LAMBDAC = apply<DecayedParticles>(event, "LAMBDAC");
  // loop over particles
  for (size_t ix = 0; ix < LAMBDAC.decaying().size(); ++ix) {
    int sign = 1, imode = 0;
    if (LAMBDAC.decaying()[ix].pid() > 0 && LAMBDAC.modeMatches(ix, 3, mode1)) {
      sign = 1;
    }
    else if (LAMBDAC.decaying()[ix].pid() < 0 && LAMBDAC.modeMatches(ix, 3, mode1CC)) {
      sign = -1;
    }
    else if (LAMBDAC.decaying()[ix].pid() > 0 && LAMBDAC.modeMatches(ix, 3, mode2)) {
      sign = 1;
      imode = 1;
    }
    else if (LAMBDAC.decaying()[ix].pid() < 0 && LAMBDAC.modeMatches(ix, 3, mode2CC)) {
      sign = -1;
      imode = 1;
    }
    else {
      continue;
    }
    const Particle& pp = LAMBDAC.decayProducts()[ix].at(sign * PID::PROTON)[0];
    const Particle& pi = LAMBDAC.decayProducts()[ix].at(imode == 0 ? 111 : sign * 211)[0];
    const Particle& KK = LAMBDAC.decayProducts()[ix].at(imode == 0 ? 310 : -sign * 321)[0];
    _h[0 + imode]->fill((pp.momentum() + KK.momentum()).mass());
    _h[2 + imode]->fill((pp.momentum() + pi.momentum()).mass());
    _h[4 + imode]->fill((KK.momentum() + pi.momentum()).mass());
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[6];
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2025_I2897384);

} ```