Rivet analyses

title: BELLE_2007_I748975

$B^+\to p \bar{\Lambda}^0\gamma$, $B^+\to p \bar{\Lambda}^0\pi^0$ and $B^0\to p \bar{\Lambda}^0\pi^-$

Experiment: BELLE (KEKB)

Inspire ID: 748975

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 76 (2007) 052004

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0 and B+ mesons, originally Upsilon(4S) decays

Mass and angular distributions in $B^+\to p \bar{\Lambda}^0\gamma$, $B^+\to p \bar{\Lambda}^0\pi^0$ and $B^0\to p \bar{\Lambda}^0\pi^-$ decays. The mass distributions, $\alpha$ parameters and average $\bar{\Lambda}^0$ energies were read from the table in the paper, while the $\cos\theta_p$ distributions were extracted from the figures.

Source code:BELLE_2007_I748975.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B-> p Lambdabar X decays class BELLE_2007_I748975 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I748975);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BB(ufs);
  BB.addStable(PID::PI0);
  BB.addStable(3122);
  BB.addStable(-3122);
  declare(BB, "BB");
  // histos
  for (unsigned int iy = 0; iy < 3; ++iy) {
    book(_h_mass[iy], 1, 1, 1 + iy);
    book(_h_cosp[iy], 2, 1, 1 + iy);
    book(_h_alpha[iy][0], 3, 1, 1 + iy);
    book(_h_alpha[iy][1], "TMP/h_alpha_" + toString(1 + iy));
    book(_h_E[iy][0], 4, 1, 1 + iy);
    book(_h_E[iy][1], "TMP/h_E_" + toString(1 + iy));
  }
  for (unsigned int iy = 0; iy < 2; ++iy) {
    book(_c[iy], "TMP/c_" + toString(iy + 1));
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles BB = apply<DecayedParticles>(event, "BB");
  // loop over particles
  for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
    int imode = 0, sign = 1, idOther = 22;
    if (BB.decaying()[ix].abspid() == 521) {
      _c[0]->fill();
      if (BB.modeMatches(ix, 3, mode1)) {
        imode = 0;
        sign = 1;
      }
      else if (BB.modeMatches(ix, 3, mode1CC)) {
        imode = 0;
        sign = -1;
      }
      else if (BB.modeMatches(ix, 3, mode2)) {
        imode = 1;
        sign = 1;
        idOther = 111;
      }
      else if (BB.modeMatches(ix, 3, mode2CC)) {
        imode = 1;
        sign = -1;
        idOther = 111;
      }
      else
        continue;
    }
    else {
      _c[1]->fill();
      if (BB.modeMatches(ix, 3, mode3)) {
        imode = 2;
        sign = 1;
        idOther = -211;
      }
      else if (BB.modeMatches(ix, 3, mode3CC)) {
        imode = 2;
        sign = -1;
        idOther = 211;
      }
      else
        continue;
    }
    const Particle& pp = BB.decayProducts()[ix].at(sign * 2212)[0];
    const Particle& lbar = BB.decayProducts()[ix].at(-sign * 3122)[0];
    const Particle& other = BB.decayProducts()[ix].at(idOther)[0];
    FourMomentum pbaryon = pp.mom() + lbar.mom();
    double mass = pbaryon.mass();
    _h_mass[imode]->fill(mass);
    // boost to B rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
        BB.decaying()[ix].mom().betaVec());
    FourMomentum pLam = boost.transform(lbar.mom());
    pbaryon = boost.transform(pbaryon);
    FourMomentum pProton = boost.transform(pp.mom());
    _h_E[imode][0]->fill(pLam.E());
    _h_E[imode][1]->fill();
    if (mass < 2.8) {
      Vector3 axis = boost.transform(other.mom()).p3().unit();
      LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(pbaryon.betaVec());
      double cosp = axis.dot(boost1.transform(pProton).p3().unit());
      _h_cosp[imode]->fill(cosp);
    }
    // finally the alpha parameter
    // Lambda decay products
    if (lbar.children().size() != 2) continue;
    Particle pbar;
    if (lbar.children()[0].pid() == -2212 && lbar.children()[1].pid() == 211) {
      pbar = lbar.children()[0];
    }
    else if (lbar.children()[1].pid() == -sign * 2212 && lbar.children()[0].pid() == sign * 211) {
      pbar = lbar.children()[1];
    }
    else {
      continue;
    }
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pLam.betaVec());
    Vector3 axis1 = -boost2.transform(boost.transform(BB.decaying()[ix].mom())).p3().unit();
    Vector3 axis2 = -boost2.transform(boost.transform(pbar.mom())).p3().unit();
    double cTheta = axis1.dot(axis2);
    _h_alpha[imode][0]->fill(1.5 * cTheta);
    _h_alpha[imode][1]->fill();
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_cosp, 1.0, false);
  scale(_h_mass[0], 1e6 / *_c[0]);
  scale(_h_mass[1], 1e6 / *_c[0]);
  scale(_h_mass[2], 1e6 / *_c[1]);
  for (unsigned int ix = 0; ix < 3; ++ix) {
    scale(_h_alpha[ix][0], 1. / *_h_alpha[ix][1]);
    scale(_h_E[ix][0], 1. / *_h_E[ix][1]);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[3], _h_cosp[3];
CounterPtr _h_alpha[3][2], _h_E[3][2];
CounterPtr _c[2];
const map<PdgId, unsigned int> mode1 = {{2212, 1}, {-3122, 1}, {22, 1}};
const map<PdgId, unsigned int> mode1CC = {{-2212, 1}, {3122, 1}, {22, 1}};
const map<PdgId, unsigned int> mode2 = {{2212, 1}, {-3122, 1}, {111, 1}};
const map<PdgId, unsigned int> mode2CC = {{-2212, 1}, {3122, 1}, {111, 1}};
const map<PdgId, unsigned int> mode3 = {{2212, 1}, {-3122, 1}, {-211, 1}};
const map<PdgId, unsigned int> mode3CC = {{-2212, 1}, {3122, 1}, {211, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2007_I748975);

} ```