Rivet analyses

m_ππ and q² distribution in B⁺ → π⁺π⁻ℓ⁺ν_ℓ

Experiment: BELLE (KEKB)

Inspire ID: 1796822

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 2005.07766

Beams: * *

Beam energies: ANY

Run details: - Any process producing the relevant decay, originally e+e- at the Upsilon(4s)

Measurement of the m_ππ and q² distributions in the B⁺ → π⁺π⁻ℓ⁺ν_ℓ decay by the BELLE collaboration

Source code:`BELLE_2020_I1796822.cc`

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

namespace Rivet {


  /// @brief B->D semileptonic decays
  class BELLE_2020_I1796822 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2020_I1796822);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(UnstableParticles(), "UFS");
      // Book histograms
      book(_h_mpipi,1,1,1);
      book(_h_q2   ,2,1,1);
      book(_nB,"/TMP/nB");
    }

    void findChildren(const Particle & p, unsigned int &ncount,
              Particles & pi, Particles & ell, Particles & nu) {
      _nB->fill();
      for (const Particle &child : p.children()) {
    if(child.children().empty()) {
      if(child.abspid()==211) {
        ++ncount;
        pi.push_back(child);
      }
      else if(child.abspid()==11 || child.abspid()==13) {
        ++ncount;
        ell.push_back(child);
      }
      else if(child.abspid()==12 || child.abspid()==14) {
        ++ncount;
        nu.push_back(child);
      }
      else if(child.pid()!=22)
        ++ncount;
    }
    // veto gamma gamma decaying mesons and K0
    else if(child.pid()==111 || child.pid()==221 || child.pid()==331 ||
        child.pid()==130 || child.pid()==310) {
      ++ncount;
    }
    else
      findChildren(child,ncount,pi,ell,nu);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::BPLUS)) {
    Particles pi,ell,nu;
    unsigned int ncount = 0;
    findChildren(p,ncount,pi,ell,nu);
    // check the decay
    // 4 outgoing
    if(ncount!=4) continue;
    // including pi+ pi-
    if(pi.size()!=2 || pi[0].pid() != -pi[1].pid()) continue;
    // and ell- nubar or ell+ nu
    if(ell.size()!=1 || nu.size()!=1) continue;
    int inu = ell[0].abspid()+1;
    if(ell[0].pid()>0) inu *=-1;
    if(nu[0].pid()!=inu) continue;
    // fill histos
    // m pipi
    FourMomentum ppi = pi[0].momentum()+pi[1].momentum();
    _h_mpipi->fill(ppi.mass());
    // q2
    FourMomentum q = p.momentum() - ppi;
    _h_q2->fill(q.mass2());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_mpipi,1e5/ *_nB);
      scale(_h_q2   ,1e5/ *_nB);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mpipi,_h_q2;
    CounterPtr _nB;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BELLE_2020_I1796822);

}

Rivet analyses

mππ and q2 distribution in B+ → π+π−ℓ+νℓ

Source code:BELLE_2020_I1796822.cc

m_ππ and q² distribution in B⁺ → π⁺π⁻ℓ⁺ν_ℓ

Source code:`BELLE_2020_I1796822.cc`