Rivet analyses

title: BELLE_2018_I1698390

Mass distribution in $\Xi_c^+\to\Xi^-\pi^+\pi^+$

Experiment: BELLE (KEKB)

Inspire ID: 1698390

Status: VALIDATED

Authors: - Peter Richardson

References: none listed

Beams: * *

Beam energies: ANY

Run details: - Any process producing Xi_c

Measurement of the $\Xi^-\pi^+$ mass distribution in $\Xi_c^+\to\Xi^-\pi^+\pi^+$. N.B. data read from figure in paper and background extracted using line on the figure subtracted.

Source code:BELLE_2018_I1698390.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Xi_c -> xi pi pi class BELLE_2018_I1698390 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2018_I1698390);


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

/// Book histograms and initialise projections before the run
void init() {
  // projection
  declare(UnstableParticles(), "UFS");
  // histo
  book(_h, 1, 1, 1);
}

void findDecay(int& sign, const Particle& parent, Particles& xi, Particles& pi, unsigned int& nstable) {
  for (const Particle& p : parent.children()) {
    if (p.pid() == sign * 3312) {
      ++nstable;
      xi.push_back(p);
    }
    else if (p.pid() == sign * 211) {
      ++nstable;
      pi.push_back(p);
    }
    else if (p.children().empty())
      ++nstable;
    else
      findDecay(sign, p, xi, pi, nstable);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid == 4232)) {
    int sign = p.pid() / p.abspid();
    Particles xi, pi;
    unsigned int nstable(0);
    findDecay(sign, p, xi, pi, nstable);
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    if (nstable == 3 && xi.size() == 1 && pi.size() == 2) {
      double p1 = boost.transform(pi[0].momentum()).p3().mod();
      double p2 = boost.transform(pi[1].momentum()).p3().mod();
      double mass = p1 > p2 ? (pi[1].momentum() + xi[0].momentum()).mass()
                            : (pi[0].momentum() + xi[0].momentum()).mass();
      _h->fill(mass);
    }
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(BELLE_2018_I1698390);

} ```