Rivet analyses

B_c⁺ → J/ψπ⁺ and B_c⁺ → J/ψπ⁺π⁺π⁻

Experiment: LHCB (LHC)

Inspire ID: 1097092

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phy.Rev.Lett. 108 (2012) 251802

Beams: * *

Beam energies: ANY

Run details: - Any process producing B_c+, originally pp

Angular distributions in between the muons B_c⁺ → J/ψπ⁺ and B_c⁺ → J/ψπ⁺π⁺π⁻ with the muons from J/ψ → μ⁺μ⁻ and mass distributions in B_c⁺ → J/ψπ⁺π⁺π⁻. The data were read from the plots in the paper and may not be corrected for efficiency and acceptance.

Source code:`LHCB_2012_I1097092.cc`

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

namespace Rivet {


  /// @brief B_c - > jpsi pi+ and pi+pi+pi-
  class LHCB_2012_I1097092 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2012_I1097092);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 541);
      declare(ufs, "UFS");
      DecayedParticles BC(ufs);
      BC.addStable(PID::PI0);
      BC.addStable(PID::K0S);
      BC.addStable(PID::JPSI);
      declare(BC, "BC");
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_h_mass[ix], 1 + ix, 1, 1);
        book(_h_ctheta[ix], 3, 1, 1 + ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{443, 1}, {211, 1}};
      static const map<PdgId, unsigned int>& mode1CC = {{443, 1}, {-211, 1}};
      static const map<PdgId, unsigned int>& mode2 = {{443, 1}, {211, 2}, {-211, 1}};
      static const map<PdgId, unsigned int>& mode2CC = {{443, 1}, {-211, 2}, {211, 1}};
      DecayedParticles BC = apply<DecayedParticles>(event, "BC");
      // loop over particles
      for (unsigned int ix = 0; ix < BC.decaying().size(); ++ix) {
        int sign = BC.decaying()[ix].pid() / BC.decaying()[ix].abspid();
        int imode = -1;
        if ((sign == 1 && BC.modeMatches(ix, 2, mode1)) || (sign == -1 && BC.modeMatches(ix, 2, mode1CC))) {
          imode = 0;
        }
        else if ((sign == 1 && BC.modeMatches(ix, 4, mode2))
                 || (sign == -1 && BC.modeMatches(ix, 4, mode2CC))) {
          const Particle& pim = BC.decayProducts()[ix].at(-sign * 211)[0];
          const Particles& pip = BC.decayProducts()[ix].at(sign * 211);
          _h_mass[0]->fill((pim.momentum() + pip[0].momentum() + pip[1].momentum()).mass());
          _h_mass[1]->fill((pim.momentum() + pip[0].momentum()).mass());
          _h_mass[1]->fill((pim.momentum() + pip[1].momentum()).mass());
          imode = 1;
        }
        else
          continue;
        // check the J/psi decay mode
        const Particle& jpsi = BC.decayProducts()[ix].at(443)[0];
        if (jpsi.children().size() != 2 || jpsi.children()[0].pid() != -jpsi.children()[1].pid()
            || jpsi.children()[0].abspid() != 13)
          continue;
        Particle muon = jpsi.children()[0].pid() == 13 ? jpsi.children()[0] : jpsi.children()[1];
        LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
            BC.decaying()[ix].momentum().betaVec());
        FourMomentum pJPsi = boost1.transform(jpsi.momentum());
        FourMomentum pMu = boost1.transform(muon.momentum());
        // to j/psi rest frame
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pJPsi.betaVec());
        Vector3 axis = pJPsi.p3().unit();
        FourMomentum pp = boost2.transform(pMu);
        // calculate angle
        double cTheta = pp.p3().unit().dot(axis);
        _h_ctheta[imode]->fill(cTheta);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 2; ++ix) {
        normalize(_h_mass[ix]);
        normalize(_h_ctheta[ix]);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[2];
    Histo1DPtr _h_ctheta[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(LHCB_2012_I1097092);

}

Rivet analyses

Bc+ → J/ψπ+ and Bc+ → J/ψπ+π+π−

Source code:LHCB_2012_I1097092.cc

B_c⁺ → J/ψπ⁺ and B_c⁺ → J/ψπ⁺π⁺π⁻

Source code:`LHCB_2012_I1097092.cc`