Rivet analyses

title: CLEOII_1994_I378319

Spectra for $D_1(2420)^+$ and $D_2^*(2460)^+$

Experiment: CLEOII (CESR)

Inspire ID: 378319

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B340 (1994) 194-204

Beams: e- e+

Beam energies: (5.3, 5.3)GeV

Run details: none listed

Measurement of the scaled momentum spectra for $D_1(2420)^+$ and $D^*_2(2460)^+$ mesons at 10.58 GeV.

Source code:CLEOII_1994_I378319.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D_1+ and D_2 spectra class CLEOII_1994_I378319 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1994_I378319);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(Beam(), "Beams");
  declare(UnstableParticles(), "UFS");
  // book histos
  book(_h_D2_cTheta, 2, 1, 1);
  book(_h_D2_x, 4, 1, 1);
  book(_h_D1_cTheta, 3, 1, 1);
  book(_h_D1_x, 4, 1, 2);
  for (unsigned int ix = 0; ix < 3; ++ix) book(_r[ix], 5, 1, ix + 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const int idD1 = 10413;
  static const int idD2 = 415;
  // Get beams and average beam momentum
  const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
  const double Emax = (beams.first.p3().mod() + beams.second.p3().mod()) / 2.0;
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  for (const Particle& p : ufs.particles(Cuts::abspid == idD1 or Cuts::abspid == idD2)) {
    if (p.abspid() == idD1) {
      // spectrum
      double Pmax = sqrt(sqr(Emax) - sqr(2.421));
      double xp = p.momentum().p3().mod() / Pmax;
      _h_D1_x->fill(xp);
    }
    else {
      double Pmax = sqrt(sqr(Emax) - sqr(2.461));
      double xp = p.momentum().p3().mod() / Pmax;
      _h_D2_x->fill(xp);
    }
    int sign = p.pid() / p.abspid();
    Particle Dstar;
    if (p.children().size() != 2) continue;
    if (p.children()[0].pid() == sign * 423 && p.children()[1].pid() == sign * 211) {
      Dstar = p.children()[0];
    }
    else if (p.children()[1].pid() == sign * 423 && p.children()[0].pid() == sign * 211) {
      Dstar = p.children()[1];
    }
    else if (p.children()[0].pid() == sign * 421 && p.children()[1].pid() == sign * 211) {
      if (p.abspid() != idD1) _r[0]->fill("10.58"s);
      continue;
    }
    else if (p.children()[1].pid() == sign * 421 && p.children()[0].pid() == sign * 211) {
      if (p.abspid() != idD1) _r[0]->fill("10.58"s);
      continue;
    }
    else {
      continue;
    }
    if (p.abspid() == idD1)
      _r[2]->fill("10.58"s);
    else
      _r[1]->fill("10.58"s);
    if (Dstar.children().size() != 2) continue;
    Particle pion;
    if (Dstar.children()[0].pid() == 111 && Dstar.children()[1].pid() == sign * 421) {
      pion = Dstar.children()[0];
    }
    else if (Dstar.children()[1].pid() == 111 && Dstar.children()[0].pid() == sign * 421) {
      pion = Dstar.children()[1];
    }
    else
      continue;
    // first boost to the D_1,2 rest frame
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    FourMomentum pDstar = boost1.transform(Dstar.momentum());
    FourMomentum pPion = boost1.transform(pion.momentum());
    // to D* rest frame
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDstar.betaVec());
    Vector3 axis = pDstar.p3().unit();
    FourMomentum pp = boost2.transform(pPion);
    // calculate angle
    double cTheta = pp.p3().unit().dot(axis);
    if (p.abspid() == idD1)
      _h_D1_cTheta->fill(cTheta);
    else
      _h_D2_cTheta->fill(cTheta);
  }
}

/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_D2_cTheta);
  normalize(_h_D2_x);
  normalize(_h_D1_cTheta);
  normalize(_h_D1_x);
  for (unsigned int ix = 0; ix < 3; ++ix) scale(_r[ix], crossSection() / sumOfWeights() / picobarn);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_D2_cTheta, _h_D2_x, _h_D1_cTheta, _h_D1_x;
BinnedHistoPtr<string> _r[3];
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOII_1994_I378319);

} ```