Rivet analyses

title: BELLE_2013_I1239347

Mass and angular distributions in the decay $B^0\to\psi(2S) K^+\pi^-$

Experiment: BELLE (KEKB)

Inspire ID: 1239347

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 88 (2013) 7, 074026

Beams: * *

Beam energies: ANY

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

Measurment of mass and angular distributions in $B^0\to\psi(2s)K^++\pi^-$ decays. The data were read from the figures in the paper and may not be corrected.

Source code:BELLE_2013_I1239347.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B0 -> psi(2S) K+ pi- class BELLE_2013_I1239347 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2013_I1239347);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
  declare(ufs, "UFS");
  DecayedParticles B0(ufs);
  B0.addStable(100443);
  declare(B0, "B0");
  // histograms
  for (unsigned int ix = 0; ix < 8; ++ix) book(_h_mass[ix], 1, 1, 1 + ix);
  book(_h_mass[8], 2, 1, 1);
  for (unsigned int ix = 0; ix < 2; ++ix) book(_h_angle[ix], 3, 1, 1 + ix);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{321, 1}, {-211, 1}, {100443, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{-321, 1}, {211, 1}, {100443, 1}};
  DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
  // loop over particles
  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& Kp = B0.decayProducts()[ix].at(321 * sign)[0];
    const Particle& pim = B0.decayProducts()[ix].at(-211 * sign)[0];
    const Particle& psi = B0.decayProducts()[ix].at(100443)[0];
    double mKpi = (Kp.momentum() + pim.momentum()).mass();
    double m2Psipi = (psi.momentum() + pim.momentum()).mass2();
    if (m2Psipi < 19.)
      _h_mass[0]->fill(sqr(mKpi));
    else if (m2Psipi >= 19. && m2Psipi < 20.5)
      _h_mass[1]->fill(sqr(mKpi));
    else if (m2Psipi >= 20.5)
      _h_mass[2]->fill(sqr(mKpi));

    if (mKpi < 0.796) {
      _h_mass[3]->fill(m2Psipi);
      _h_mass[8]->fill(m2Psipi);
    }
    else if (mKpi >= 0.796 && mKpi < 0.996)
      _h_mass[4]->fill(m2Psipi);
    else if (mKpi >= 0.996 && mKpi < 1.332) {
      _h_mass[5]->fill(m2Psipi);
      _h_mass[8]->fill(m2Psipi);
    }
    else if (mKpi >= 1.332 && mKpi < 1.532)
      _h_mass[6]->fill(m2Psipi);
    else if (mKpi >= 1.532) {
      _h_mass[7]->fill(m2Psipi);
      _h_mass[8]->fill(m2Psipi);
    }
    // need leptonic psi' decay for angular dists
    if (psi.children().size() != 2 || psi.children()[0].pid() != -psi.children()[1].pid()
        || (psi.children()[0].abspid() != 11 && psi.children()[0].abspid() != 11))
      vetoEvent;
    Particle lm = psi.children()[0];
    Particle lp = psi.children()[1];
    if (lm.pid() < 0) swap(lm, lp);
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
        B0.decaying()[ix].momentum().betaVec());
    FourMomentum pKstar = boost1.transform(Kp.momentum() + pim.momentum());
    FourMomentum pPsi = boost1.transform(psi.momentum());
    // trans vector in K* frame
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
    FourMomentum pKp = boost2.transform(boost1.transform(Kp.momentum()));
    Vector3 axis1 = pKstar.p3().unit();
    double cTheta1 = axis1.dot(pKp.p3().unit());
    Vector3 trans1 = pKp.p3() - cTheta1 * pKp.p3().mod() * axis1;
    // leptons in psi' frame
    LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPsi.betaVec());
    FourMomentum plm = boost3.transform(boost1.transform(lm.momentum()));
    double cTheta2 = axis1.dot(plm.p3().unit());
    Vector3 trans2 = plm.p3() - cTheta2 * plm.p3().mod() * axis1;
    _h_angle[0]->fill(cTheta2);
    // angle between planes
    double chi = atan2(trans1.cross(trans2).dot(axis1), trans1.dot(trans2));
    _h_angle[1]->fill(chi);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 9; ++ix) normalize(_h_mass[ix], 1., false);
  normalize(_h_angle[0], 1., false);
  normalize(_h_angle[1], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[9], _h_angle[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2013_I1239347);

} ```