Rivet analyses

Proton and Λ momentum spectrum in B decays

Experiment: ARGUS (DORIS)

Inspire ID: 334962

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Z.Phys.C 56 (1992) 1-6

Beams: * *

Beam energies: ANY

Run details: - Any processs producing Upslion(4S), originally e+e-

Measurement of the proton and Λ momentum spectrum in B decays by ARGUS. The corrected data were read from the figures in the paper.

Source code:ARGUS_1992_I334962.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief B-> baryons
  class ARGUS_1992_I334962 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1992_I334962);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(), "UFS");
      // histos
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_h_spect[ix], 1 + ix, 1, 1);
        book(_h_flav[ix], 3, 1, 1 + ix);
      }
    }

    void findDecayProducts(const Particle& parent,
                           Particles& protons_all,
                           Particles& protons_charm,
                           Particles& protons_had,
                           Particles& lambda,
                           bool cBaryon = false) {
      for (const Particle& p : parent.children()) {
        if (p.abspid() == PID::PROTON) {
          protons_all.push_back(p);
          if (cBaryon)
            protons_charm.push_back(p);
          else
            protons_had.push_back(p);
        }
        else if (p.abspid() == PID::LAMBDA) {
          lambda.push_back(p);
          continue;
        }
        else if (!p.children().empty()) {
          bool cBaryonDec = cBaryon || (PID::isCharmHadron(p.pid()) && p.abspid() % 2 == 0);
          findDecayProducts(p, protons_all, protons_charm, protons_had, lambda, cBaryonDec);
        }
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Find the upsilons
      for (const Particle& ups : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid == 300553)) {
        Particles protons[3], lambda;
        findDecayProducts(ups, protons[0], protons[1], protons[2], lambda);
        LorentzTransform boost;
        if (ups.p3().mod() > 1 * MeV) {
          boost = LorentzTransform::mkFrameTransformFromBeta(ups.mom().betaVec());
        }
        for (const Particle& p : protons[0]) {
          double pcm = boost.transform(p.mom()).p3().mod();
          _h_spect[0]->fill(pcm);
        }
        for (const Particle& p : lambda) {
          double pcm = boost.transform(p.mom()).p3().mod();
          _h_spect[1]->fill(pcm);
        }
        for (unsigned int ix = 0; ix < 2; ++ix) {
          for (const Particle& p : protons[ix + 1]) {
            double pcm = boost.transform(p.mom()).p3().mod();
            _h_flav[ix]->fill(pcm);
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_spect, 1.0, false);
      normalize(_h_flav, 1.0, false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_spect[2], _h_flav[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ARGUS_1992_I334962);

}