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`