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/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.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`