Rivet analyses

title: BELLE_2024_I2778312

Mass and angular distributions in $B^-\to D^0\pi^-\pi^0$ in the $\rho$ region

Experiment: BELLE (KEKB)

Inspire ID: 2778312

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 109 (2024) 11, L111103 - arXiv: 2404.10874

Beams: * *

Beam energies: ANY

Run details: - Any process producing B mesons, originally Upsilon(4S) decays

Measurement of the mass and angular distribution in $B^-\to D^0\pi^-\pi^0$ decays in the $\rho$ region

Source code:BELLE_2024_I2778312.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> D rho class BELLE_2024_I2778312 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2024_I2778312);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == -521);
  declare(ufs, "UFS");
  DecayedParticles BP(ufs);
  BP.addStable(421);
  BP.addStable(111);
  declare(BP, "BP");
  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) {
  DecayedParticles BP = apply<DecayedParticles>(event, "BP");
  for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
    if (!BP.modeMatches(ix, 3, mode)) continue;
    const Particle& pim = BP.decayProducts()[ix].at(-211)[0];
    const Particle& pi0 = BP.decayProducts()[ix].at(111)[0];
    // compute the helicity angles
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
        BP.decaying()[ix].mom().betaVec());

    // pi pi mass and angle
    FourMomentum ppipi = pim.mom() + pi0.mom();
    ppipi = boost1.transform(ppipi);
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
    FourMomentum pPi = boost1.transform(pim.mom());
    FourMomentum pPi3 = boost2.transform(pPi);
    double cTheta = -pPi3.p3().unit().dot(ppipi.p3().unit());
    if (cTheta > 0.7) continue;
    _h[0]->fill(cTheta);
    _h[1]->fill(ppipi.mass() / GeV);
  }
}


/// 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];
const map<PdgId, unsigned int> mode = {{-211, 1}, {111, 1}, {421, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2024_I2778312);

} ```