Rivet analyses

title: BELLE_2008_I768236

$B\to D^*\ell\nu_\ell$ decays

Experiment: BELLE (KEKB)

Inspire ID: 768236

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 77 (2008) 091503

Beams: * *

Beam energies: ANY

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

Measurement of the hadronic mass, helicity and $w$ distributions for $B\to D^*\ell\nu_\ell$ decays. The background subtracted data was read from the plots in the paper.

Source code:BELLE_2008_I768236.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> D** l nu class BELLE_2008_I768236 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2008_I768236);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BB(ufs);
  BB.addStable(411);
  BB.addStable(-411);
  BB.addStable(421);
  BB.addStable(-421);
  BB.addStable(413);
  BB.addStable(-413);
  BB.addStable(423);
  BB.addStable(-423);
  BB.addStable(PID::PI0);
  declare(BB, "BB");
  // hists
  for (unsigned int ix = 0; ix < 4; ++ix) {
    book(_h_mass[ix], 1, 1, 1 + ix);
    if (ix == 3 || ix == 1) continue;
    book(_h_hel[ix], 2, 1, 1 + ix);
    book(_h_w[ix], 3, 1, 1 + ix);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int> mode1[4] = {{{-411, 1}, {211, 1}, {-11, 1}, {12, 1}},
                                                    {{411, 1}, {-211, 1}, {11, 1}, {-12, 1}},
                                                    {{-411, 1}, {211, 1}, {-13, 1}, {14, 1}},
                                                    {{411, 1}, {-211, 1}, {13, 1}, {-14, 1}}};
  static const map<PdgId, unsigned int> mode2[4] = {{{-413, 1}, {211, 1}, {-11, 1}, {12, 1}},
                                                    {{413, 1}, {-211, 1}, {11, 1}, {-12, 1}},
                                                    {{-413, 1}, {211, 1}, {-13, 1}, {14, 1}},
                                                    {{413, 1}, {-211, 1}, {13, 1}, {-14, 1}}};
  static const map<PdgId, unsigned int> mode3[4] = {{{-421, 1}, {-211, 1}, {-11, 1}, {12, 1}},
                                                    {{421, 1}, {211, 1}, {11, 1}, {-12, 1}},
                                                    {{-421, 1}, {-211, 1}, {-13, 1}, {14, 1}},
                                                    {{421, 1}, {211, 1}, {13, 1}, {-14, 1}}};
  static const map<PdgId, unsigned int> mode4[4] = {{{-423, 1}, {-211, 1}, {-11, 1}, {12, 1}},
                                                    {{423, 1}, {211, 1}, {11, 1}, {-12, 1}},
                                                    {{-423, 1}, {-211, 1}, {-13, 1}, {14, 1}},
                                                    {{423, 1}, {211, 1}, {13, 1}, {-14, 1}}};
  // loop over B mesons
  DecayedParticles BB = apply<DecayedParticles>(event, "BB");
  // loop over particles
  for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
    for (unsigned int il = 0; il < 4; ++il) {
      int iD, imode = 0;
      if (BB.modeMatches(ix, 4, mode1[il])) {
        imode = 0;
        iD = 411;
      }
      else if (BB.modeMatches(ix, 4, mode2[il])) {
        imode = 1;
        iD = 413;
      }
      else if (BB.modeMatches(ix, 4, mode3[il])) {
        imode = 2;
        iD = 421;
      }
      else if (BB.modeMatches(ix, 4, mode4[il])) {
        imode = 3;
        iD = 423;
      }
      else
        continue;
      int sign = il % 2 == 0 ? 1 : -1;
      int ipi = -sign * 211;
      iD *= -sign;
      if (imode < 2) ipi *= -1;
      const Particle& pi1 = BB.decayProducts()[ix].at(ipi)[0];
      const Particle& DD = BB.decayProducts()[ix].at(iD)[0];
      FourMomentum pHad = pi1.mom() + DD.mom();
      double mass = pHad.mass();
      _h_mass[imode]->fill(mass);
      // just the D pi modes for helicty and w
      if (imode % 2 != 0) continue;
      // check ingtermediate
      int inter = -1;
      for (unsigned int iz = 0; iz < BB.decaying()[ix].children().size(); ++iz) {
        if (BB.decaying()[ix].children()[iz].abspid() == 10411
            || BB.decaying()[ix].children()[iz].abspid() == 10421) {
          inter = 0;
          break;
        }
        else if (BB.decaying()[ix].children()[iz].abspid() == 415
                 || BB.decaying()[ix].children()[iz].abspid() == 425) {
          inter = 2;
          break;
        }
      }
      if (inter < 0) continue;
      // First boost all relevant momenta into the B-rest frame
      const LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
          BB.decaying()[ix].mom().betaVec());
      // Momenta in B rest frame:
      FourMomentum pDSS = boost1.transform(pHad);
      FourMomentum pW = boost1.transform(BB.decaying()[ix].mom() - pHad);
      FourMomentum ppi = boost1.transform(pi1);
      const LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDSS.betaVec());
      double ctheta = pW.p3().unit().dot(boost2.transform(ppi).p3().unit());
      _h_hel[inter]->fill(abs(ctheta));
      double mB2 = BB.decaying()[ix].mom().mass2();
      double mD2 = sqr(mass);
      double w = (mB2 + mD2 - pW.mass2()) / (2. * sqrt(mB2) * sqrt(mD2));
      _h_w[inter]->fill(w);
    }
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[4], _h_hel[3], _h_w[3];
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2008_I768236);

} ```