Rivet analyses

title: BELLE_2008_I756554

Mass and angular distributions in $B^+\to D^0\bar{D}^0K^+$

Experiment: BELLE (KEKB)

Inspire ID: 756554

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 100 (2008) 092001

Beams: * *

Beam energies: ANY

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

Measurement of mass and angular distributions in $B^+\to D^0\bar{D}^0K^+$ decays by the BaBar collaboration. The efficiency corrected, background subtracted, data were read from Figures 3 and 4. The PDG code for the $D_s(2700)$ is not defined but we make the assumption it is the vector $2S$ state with PDG code 100433, although this can b e changed using the PID option.

Source code:BELLE_2008_I756554.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B+ -> D0 Dbar0 K+ class BELLE_2008_I756554 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2008_I756554);


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

/// Book histograms and initialise projections before the run
void init() {
  // set the PDG code
  _pid = getOption<int>("PID", 100433);
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BP(ufs);
  BP.addStable(421);
  BP.addStable(-421);
  declare(BP, "BP");
  // histos
  for (unsigned int ix = 0; ix < 3; ++ix) {
    book(_h_mass[ix], 1, 1, 1 + ix);
  }
  book(_h_angle, 2, 1, 1);
  book(_c, "TMP/c");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles BP = apply<DecayedParticles>(event, "BP");
  // loop over particles
  for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
    int sign = 1;
    if (BP.modeMatches(ix, 3, mode))
      sign = 1;
    else if (BP.modeMatches(ix, 3, modeCC))
      sign = -1;
    else
      continue;
    const Particle& Kp = BP.decayProducts()[ix].at(sign * 321)[0];
    const Particle& D0 = BP.decayProducts()[ix].at(sign * 421)[0];
    const Particle& Dbar0 = BP.decayProducts()[ix].at(-sign * 421)[0];
    _c->fill();
    FourMomentum pDD = D0.mom() + Dbar0.mom();
    double mDD = pDD.mass();
    _h_mass[0]->fill(mDD);
    FourMomentum pDK = D0.mom() + Kp.mom();
    if (mDD > 3.85) _h_mass[2]->fill(pDK.mass());
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
        BP.decaying()[ix].mom().betaVec());
    pDD = boost1.transform(pDD);
    // boost to DD frame
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDD.betaVec());
    FourMomentum pD = boost2.transform(boost1.transform(D0.mom()));
    // helicity angle
    double cTheta = pDD.p3().unit().dot(pD.p3().unit());
    if (cTheta > 0) _h_mass[1]->fill(mDD);
    // check for intermediate DS
    bool Ds2700 = false;
    for (const Particle& child : BP.decaying()[ix].children()) {
      Ds2700 |= child.abspid() == _pid;
    }
    if (!Ds2700) continue;
    pDK = boost1.transform(pDK);
    LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pDK.betaVec());
    FourMomentum pK = boost3.transform(boost1.transform(Kp.mom()));
    cTheta = pDK.p3().unit().dot(pK.p3().unit());
    _h_angle->fill(cTheta);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_mass, 1.0 / *_c);
  normalize(_h_angle);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[3], _h_angle;
CounterPtr _c;
int _pid;
const map<PdgId, unsigned int> mode = {{421, 1}, {-421, 1}, {321, 1}};
const map<PdgId, unsigned int> modeCC = {{421, 1}, {-421, 1}, {-321, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2008_I756554);

} ```