Rivet analyses

title: BELLE_2007_I733011

$\bar{B}^0\to D^0\pi^+\pi^-$

Experiment: BELLE (KEKB)

Inspire ID: 733011

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 76 (2007) 012006

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0, originally upsilno(4S)

Measurement of mass and angular distributions in $\bar{B}^0\to D^0\pi^+\pi^-$. The data were read from the plots in the paper and the given backgrounds subtracted, however the data is not efficiency corrected.

Source code:BELLE_2007_I733011.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Bbar0 -> D0 pi+ pi- class BELLE_2007_I733011 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I733011);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
  declare(ufs, "UFS");
  DecayedParticles B0(ufs);
  B0.addStable(421);
  B0.addStable(-421);
  declare(B0, "B0");
  // histos
  for (unsigned int ix = 0; ix < 3; ++ix) {
    book(_h_pipi[ix], 3, 1, 1 + ix);
    if (ix == 2) continue;
    book(_h_mass[ix], 1, 1, 1 + ix);
    book(_h_Dpi[ix], 2, 1, 1 + ix);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
  for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
    int sign = 1;
    if (B0.decaying()[ix].pid() > 0 && B0.modeMatches(ix, 3, mode))
      sign = 1;
    else if (B0.decaying()[ix].pid() < 0 && B0.modeMatches(ix, 3, modeCC))
      sign = -1;
    else {
      continue;
    }
    const Particle& pip = B0.decayProducts()[ix].at(sign * 211)[0];
    const Particle& pim = B0.decayProducts()[ix].at(-sign * 211)[0];
    const Particle& D0 = B0.decayProducts()[ix].at(-sign * 421)[0];
    // compute the helicity angles
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
        B0.decaying()[ix].mom().betaVec());
    // D pi mass and angle
    FourMomentum pDpi = D0.mom() + pim.mom();
    double mDpi = pDpi.mass();
    pDpi = boost1.transform(pDpi);
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDpi.betaVec());
    FourMomentum pD = boost2.transform(boost1.transform(D0.mom()));
    double cDpi = pD.p3().unit().dot(pDpi.p3().unit());
    // fill histos
    if (abs(mDpi - 2.46) < .1)
      _h_Dpi[0]->fill(cDpi);
    else if (abs(mDpi - 2.30) < .1)
      _h_Dpi[1]->fill(cDpi);
    if (cDpi > 0.) _h_mass[0]->fill(mDpi);
    // pi pi mass and angle
    FourMomentum ppipi = pim.mom() + pip.mom();
    double mpipi = ppipi.mass();
    ppipi = boost1.transform(ppipi);
    LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
    FourMomentum ppip = boost3.transform(boost1.transform(pip.mom()));
    double cpipi = -ppip.p3().unit().dot(ppipi.p3().unit());
    // fill angles
    if (abs(mpipi - 0.78) < 0.2)
      _h_pipi[0]->fill(cpipi);
    else if (abs(mpipi - 1.20) < 0.1)
      _h_pipi[1]->fill(cpipi);
    else if (mpipi < 0.6)
      _h_pipi[2]->fill(cpipi);
    if (cpipi > 0.) _h_mass[1]->fill(mpipi);
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[2], _h_Dpi[2], _h_pipi[3];
const map<PdgId, unsigned int> mode = {{211, 1}, {-211, 1}, {-421, 1}};
const map<PdgId, unsigned int> modeCC = {{211, 1}, {-211, 1}, {421, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2007_I733011);

} ```