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BELLE_2024_I2810686

Differential branching ratio in $B^0\to\pi^-\ell^+\nu_\ell$ and $B^+\to\rho^0\ell^+\nu_\ell$
Experiment: BELLE (KEKB)
Inspire ID: 2810686
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
No references listed
Beams: * *
Beam energies: ANY
Run details:
  • Events with B-decays, either particle guns or collisions, originally e+e- at the Upsilon(4S)

Differential branching ratio in $B^0\to\pi^-\ell^+\nu_\ell$ and $B^+\to\rho^0\ell^+\nu_\ell$

Source code: BELLE_2024_I2810686.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4
  5namespace Rivet {
  6
  7
  8  /// @brief B0 -> pi- and B+ rho0 semi-leptonic
  9  class BELLE_2024_I2810686 : public Analysis {
 10  public:
 11
 12    /// Constructor
 13    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2024_I2810686);
 14
 15
 16    /// @name Analysis methods
 17    /// @{
 18
 19    /// Book histograms and initialise projections before the run
 20    void init() {
 21
 22      // Initialise and register projections
 23      declare(UnstableParticles(), "UFS");
 24      for(unsigned int ix=0;ix<2;++ix) {
 25        book(_h[ix],1,1,1+ix);
 26        book(_c[ix],"TMP/c_"+toString(ix));
 27      }
 28    }
 29
 30    // Calculate the Q2 using mother and daugher meson
 31    double q2(const Particle& B, int mesonID) {
 32      FourMomentum q = B.mom() - select(B.children(), Cuts::pid==mesonID)[0];
 33      return q*q;
 34    }
 35
 36    // Check for explicit decay into pdgids
 37    bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
 38      // Trivial check to ignore any other decays but the one in question modulo photons
 39      const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
 40      if (children.size()!=ids.size()) return false;
 41      // Check for the explicit decay
 42      return all(ids, [&](int i){return count(children, hasPID(i))==1;});
 43    }
 44
 45    /// Perform the per-event analysis
 46    void analyze(const Event& event) {
 47      // Loop over B0 Mesons
 48      for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==PID::B0)) {
 49        _c[0]->fill();
 50        if(p.pid()<0) {
 51          if (isSemileptonicDecay(p, {PID::PIPLUS, PID::ELECTRON, PID::NU_EBAR}) ||
 52              isSemileptonicDecay(p, {PID::PIPLUS, PID::MUON,     PID::NU_MUBAR})) {
 53            _h[0]->fill(q2(p, PID::PIPLUS));
 54          }
 55        }
 56        else {
 57          if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E }) ||
 58              isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU})) {
 59            _h[0]->fill(q2(p, PID::PIMINUS));
 60          }
 61        }
 62      }
 63      for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==PID::BPLUS)) {
 64        _c[1]->fill();
 65        if(p.pid()<0) {
 66          if (isSemileptonicDecay(p, {PID::RHO0, PID::ELECTRON, PID::NU_EBAR}) ||
 67              isSemileptonicDecay(p, {PID::RHO0, PID::MUON,     PID::NU_MUBAR})) {
 68            _h[1]->fill(q2(p, PID::RHO0));
 69          }
 70        }
 71        else {
 72          if (isSemileptonicDecay(p, {PID::RHO0, PID::POSITRON, PID::NU_E }) ||
 73              isSemileptonicDecay(p, {PID::RHO0, PID::ANTIMUON, PID::NU_MU})) {
 74            _h[1]->fill(q2(p, PID::RHO0));
 75          }
 76        }
 77      }
 78    }
 79
 80
 81    /// Normalise histograms etc., after the run
 82    void finalize() {
 83      for(unsigned int ix=0;ix<2;++ix) {
 84        scale(_h[ix], 0.5e4/ *_c[ix]);
 85      }
 86    }
 87
 88    /// @}
 89
 90
 91    /// @name Histograms
 92    /// @{
 93    Histo1DPtr _h[2];
 94    CounterPtr _c[2];
 95    /// @}
 96
 97
 98  };
 99
100
101  RIVET_DECLARE_PLUGIN(BELLE_2024_I2810686);
102
103}