Rivet analyses

Mass distributions in B− → Λc+p̄π−

Experiment: BELLE (KEKB)

Inspire ID: 658082

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 242001

Beams: * *

Beam energies: ANY

Run details: none listed

Measurement of mass distributions in B− → Λc+p̄π−. The mass distributions were read from figure 2, which is not corrected, while the corrected helicity distribution was read from figure 3.

Source code:BELLE_2006_I658082.cc

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

namespace Rivet {


  /// @brief B- -> Lambdac+ pbar pi-
  class BELLE_2006_I658082 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2006_I658082);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 521);
      declare(ufs, "UFS");
      DecayedParticles BP(ufs);
      // treat Lambda_c, Sigma_c and sigma_c* as stable
      BP.addStable(4122);
      BP.addStable(-4122);
      declare(BP, "BP");
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_h[ix], 1, 1, 1 + ix);
      }
      book(_h[2], 2, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
      // loop over particles
      for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
        int sign = 1;
        if (BP.decaying()[ix].pid() < 0 && BP.modeMatches(ix, 3, mode))
          sign = 1;
        else if (BP.decaying()[ix].pid() > 0 && BP.modeMatches(ix, 3, modeCC))
          sign = -1;
        else
          continue;
        const Particle& lamC = BP.decayProducts()[ix].at(sign * 4122)[0];
        const Particle& pbar = BP.decayProducts()[ix].at(-sign * 2212)[0];
        const Particle& pim = BP.decayProducts()[ix].at(-sign * 211)[0];
        double mLamCPi = (lamC.mom() + pim.mom()).mass();
        double mPbarPi = (pbar.mom() + pim.mom()).mass();
        double mLamCPB = (lamC.mom() + pbar.mom()).mass();
        if (mLamCPi > 2.6 && mLamCPB > 3.5) _h[0]->fill(mPbarPi);
        if (mLamCPi > 2.6 && mPbarPi > 1.6) _h[1]->fill(mLamCPB);
        if (mLamCPB < 3.6) {
          LorentzTransform boostB = LorentzTransform::mkFrameTransformFromBeta(
              BP.decaying()[ix].mom().betaVec());
          FourMomentum pLamC = boostB.transform(lamC.mom());
          FourMomentum pLamCPB = boostB.transform(lamC.mom() + pbar.mom());
          LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pLamCPB.betaVec());
          pLamC = boost2.transform(pLamC);
          double cTheta = pLamC.p3().unit().dot(pLamCPB.p3().unit());
          _h[2]->fill(cTheta);
        }
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[3];
    const map<PdgId, unsigned int> mode = {{4122, 1}, {-2212, 1}, {-211, 1}};
    const map<PdgId, unsigned int> modeCC = {{-4122, 1}, {2212, 1}, {211, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2006_I658082);

}