Rivet analyses

title: BELLE_2004_I623102

Mass and angular distributions in $B^-\to D^{(*)+}\pi^-\pi^-$

Experiment: BELLE (KEKB)

Inspire ID: 623102

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 69 (2004) 112002

Beams: * *

Beam energies: ANY

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

Mass and angular distributions in $B^-\to D^{(*)+}\pi^-\pi^-$. The data were read from the figures in the paper and the backgrounds given subtracted.

Source code:BELLE_2004_I623102.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> D** pi class BELLE_2004_I623102 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2004_I623102);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BP(ufs);
  BP.addStable(411);
  BP.addStable(-411);
  BP.addStable(413);
  BP.addStable(-413);
  declare(BP, "BP");
  // histograms
  book(_h_mass[0], 1, 1, 1);
  book(_h_mass[1], 4, 1, 1);
  book(_b_mass, {-1., -0.67, -0.33, 0, 0.33, 0.67, 1.});
  for (unsigned int ix = 0; ix < 6; ++ix) {
    book(_b_mass->bin(ix + 1), 2, 1, 1 + ix);
  }
  for (unsigned int iy = 0; iy < 4; ++iy) {
    if (iy == 0)
      book(_b_angle[0], {0., 5., 5.9, 6.2, 400});
    else
      book(_b_angle[iy], {0., 5.76, 5.98, 6.15, 400});
    for (unsigned int ix = 0; ix < 4; ++ix) {
      if (iy == 0)
        book(_b_angle[0]->bin(ix + 1), 3, 1, 1 + ix);
      else
        book(_b_angle[iy]->bin(ix + 1), 5, iy, 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) {
    int sign = BP.decaying()[ix].pid() / BP.decaying()[ix].abspid();
    int imode = 0;
    if (sign > 0 && BP.modeMatches(ix, 3, mode1))
      imode = 0;
    else if (sign < 0 && BP.modeMatches(ix, 3, mode1CC))
      imode = 0;
    else if (sign > 0 && BP.modeMatches(ix, 3, mode2))
      imode = 1;
    else if (sign < 0 && BP.modeMatches(ix, 3, mode2CC))
      imode = 1;
    else
      continue;
    const Particles& pip = BP.decayProducts()[ix].at(sign * 211);
    const Particle& Dm = BP.decayProducts()[ix].at(-sign * (411 + imode * 2))[0];
    // find the mnimum Dpi mass
    double mDpi[2] = {(Dm.mom() + pip[0].mom()).mass(), (Dm.mom() + pip[1].mom()).mass()};
    unsigned int iloc = 0;
    if (mDpi[0] > mDpi[1]) {
      iloc = 1;
      swap(mDpi[0], mDpi[1]);
    }
    _h_mass[imode]->fill(mDpi[0]);
    // compute the helicity angles
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
        BP.decaying()[ix].mom().betaVec());
    // D pi mass and angle
    FourMomentum pDpi = Dm.mom() + pip[iloc].mom();
    pDpi = boost1.transform(pDpi);
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDpi.betaVec());
    FourMomentum pPi = boost1.transform(pip[iloc].mom());
    FourMomentum pPi3 = boost2.transform(pPi);
    double cDpi = -pPi3.p3().unit().dot(pDpi.p3().unit());
    // fill histos
    if (imode == 0) {
      _b_mass->fill(cDpi, mDpi[0]);
      _b_angle[0]->fill(sqr(mDpi[0]), cDpi);
    }
    else {
      _b_angle[1]->fill(sqr(mDpi[0]), cDpi);
      // find the pion from the D* decay
      Particle pi2;
      if (Dm.children().size() != 2) continue;
      if ((Dm.children()[0].pid() == -sign * 411 || Dm.children()[0].pid() == -sign * 411)
          && (Dm.children()[1].pid() == -sign * 211 || Dm.children()[1].pid() == 111)) {
        pi2 = Dm.children()[1];
      }
      else if ((Dm.children()[1].pid() == -sign * 411 || Dm.children()[1].pid() == -sign * 411)
               && (Dm.children()[0].pid() == -sign * 211 || Dm.children()[0].pid() == 111)) {
        pi2 = Dm.children()[0];
      }
      else {
        continue;
      }
      FourMomentum pPi2 = boost1.transform(pi2.mom());
      FourMomentum pDm = boost1.transform(Dm.mom());
      Vector3 axis = pDm.p3().unit();
      Vector3 trans1 = pPi.p3() - pPi.p3().dot(axis) * axis;
      Vector3 trans2 = pPi2.p3() - pPi2.p3().dot(axis) * axis;
      const double chi = atan2(trans1.cross(trans2).dot(axis), trans1.dot(trans2));
      _b_angle[3]->fill(sqr(mDpi[0]), chi);
      pDm = boost2.transform(pDm);
      pPi2 = boost2.transform(pPi2);
      LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pDm.betaVec());
      pPi2 = boost3.transform(pPi2);
      const double cTheta = pPi2.p3().unit().dot(pPi3.p3().unit());
      _b_angle[2]->fill(sqr(mDpi[0]), cTheta);
    }
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[2];
Histo1DGroupPtr _b_mass, _b_angle[4];
const map<PdgId, unsigned int> mode1 = {{211, 2}, {-411, 1}};
const map<PdgId, unsigned int> mode1CC = {{-211, 2}, {411, 1}};
const map<PdgId, unsigned int> mode2 = {{211, 2}, {-413, 1}};
const map<PdgId, unsigned int> mode2CC = {{-211, 2}, {413, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2004_I623102);

} ```