Rivet analyses

title: BELLE_2021_I1917200

Leptonic mass moments in $B\to X_c\ell\nu$ decays

Experiment: BELLE (KEKB)

Inspire ID: 1917200

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.D 104 (2021) 11, 112011

Beams: * *

Beam energies: ANY

Run details: - B meson production in Upsilon(4S) decays

Measurement of leptonic mass moments in $B\to X_c\ell\nu$ decays.

Source code:BELLE_2021_I1917200.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> c l nu moments class BELLE_2021_I1917200 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2021_I1917200);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521), "UFS");
  // histos
  for (unsigned int il = 0; il < 2; ++il) {
    for (unsigned int ix = 0; ix < 4; ++ix) {
      book(_p[il][ix], 4 * il + 1 + ix, 1, 1);
    }
    for (unsigned int ix = 4; ix < 8; ++ix) {
      book(_p[il][ix], "TMP/p_" + toString(il) + "_" + toString(ix),
           refData<YODA::BinnedEstimate<string>>(4 * il + 1, 1, 1));
    }
  }
}

void findDecayProducts(const Particle& parent,
                       Particles& em,
                       Particles& ep,
                       Particles& nue,
                       Particles& nueBar,
                       bool& charm) {
  for (const Particle& p : parent.children()) {
    if (PID::isCharmHadron(p.pid())) {
      charm = true;
    }
    else if (p.pid() == PID::EMINUS || p.pid() == PID::MUON) {
      em.push_back(p);
    }
    else if (p.pid() == PID::EPLUS || p.pid() == PID::ANTIMUON) {
      ep.push_back(p);
    }
    else if (p.pid() == PID::NU_E || p.pid() == PID::NU_MU) {
      nue.push_back(p);
    }
    else if (p.pid() == PID::NU_EBAR || p.pid() == PID::NU_MUBAR) {
      nueBar.push_back(p);
    }
    else if (PID::isBottomHadron(p.pid())) {
      findDecayProducts(p, em, ep, nue, nueBar, charm);
    }
    else if (!PID::isHadron(p.pid())) {
      findDecayProducts(p, em, ep, nue, nueBar, charm);
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  if (_edges.empty()) _edges = _p[0][0]->xEdges();
  // find and loop over Upslion(4S)
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
    if (p.children().empty() || (p.children().size() == 1 && p.children()[1].abspid() == p.abspid())) {
      continue;
    }
    // find decay products
    bool charm = false;
    Particles em, ep, nue, nueBar;
    findDecayProducts(p, em, ep, nue, nueBar, charm);
    if (!charm) continue;
    FourMomentum pl, pnu;
    unsigned int il = 0;
    if (em.size() == 1 && nueBar.size() == 1 && em[0].pid() + 1 == -nueBar[0].pid()) {
      pl = em[0].momentum();
      pnu = nueBar[0].momentum();
      if (em[0].abspid() == 13) il = 1;
    }
    else if (ep.size() == 1 && nue.size() == 1 && nue[0].pid() == -ep[0].pid() + 1) {
      pl = ep[0].momentum();
      pnu = nue[0].momentum();
      if (ep[0].abspid() == 13) il = 1;
    }
    else {
      continue;
    }
    double q2 = (pl + pnu).mass2();
    vector<double> q2n(8);
    for (unsigned int ix = 0; ix < 8; ++ix) q2n[ix] = pow(q2, 1 + ix);
    if (q2 < 3.0) continue;
    double q2cut = 3.0;
    for (unsigned int ibin = 0; ibin < 15; ++ibin) {
      if (q2 > q2cut) {
        for (unsigned int ix = 0; ix < 8; ++ix) {
          _p[il][ix]->fill(_edges[ibin], q2n[ix]);
        }
      }
      else {
        break;
      }
      q2cut += 0.5;
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int il = 0; il < 2; ++il) {
    BinnedEstimatePtr<string> tmp[3];
    for (unsigned int ix = 0; ix < 3; ++ix) book(tmp[ix], 3 * il + 9 + ix, 1, 1);
    for (unsigned int iy = 0; iy < _p[il][0]->numBins(); ++iy) {
      const double N = _p[il][0]->bin(iy + 1).effNumEntries();
      double q2 = _p[il][0]->bin(iy + 1).mean(2), q4 = _p[il][1]->bin(iy + 1).mean(2),
             q6 = _p[il][2]->bin(iy + 1).mean(2), q8 = _p[il][3]->bin(iy + 1).mean(2),
             q10 = _p[il][4]->bin(iy + 1).mean(2), q12 = _p[il][5]->bin(iy + 1).mean(2),
             q14 = _p[il][6]->bin(iy + 1).mean(2), q16 = _p[il][7]->bin(iy + 1).mean(2);
      // q4 case
      if (N <= 9) continue; // q8 needs 8 events + Bessel correction
      double value = q4 - sqr(q2);
      double error = (-sqr(q4) + 4 * sqr(q2) * (-sqr(q2) + 2 * q4) - 4 * q2 * q6 + q8) / N;
      tmp[0]->bin(iy + 1).set(value, sqrt(error));
      // q6 case
      if (N <= 13) continue; // q12 needs 12 events + Bessel correction
      value = q6 + q2 * (2 * sqr(q2) - 3 * q4);
      error = (q12 - sqr(q6) - 6 * q2 * (q10 - 5 * q4 * q6) + 3 * q4 * (3 * sqr(q4) - 2 * q8)
               + sqr(q2) * (-72 * sqr(q4) + 36 * sqr(q2) * (-sqr(q2) + 3 * q4) - 48 * q2 * q6 + 21 * q8))
          / N;
      tmp[1]->bin(iy + 1).set(value, sqrt(error));
      // q8 case
      if (N <= 17) continue; // q16 needs 16 events + Bessel correction
      value = q8 + q2 * (-3 * q2 * sqr(q2) + 6 * q2 * q4 - 4 * q6);
      error = (q16 - 8 * q6 * (q10 - 2 * q4 * q6) - sqr(q8)
               - 8 * q2 * (q14 - 3 * q4 * (q10 - 4 * q4 * q6) - 6 * q6 * q8)
               + 4 * sqr(q2)
                   * (7 * q12 - 28 * sqr(q6) + 6 * q2 * (-3 * q10 + 22 * q4 * q6)
                      + 3 * q4 * (12 * sqr(q4) - 11 * q8)
                      + 3 * sqr(q2)
                          * (-12 * sqr(q2) * (sqr(q2) - 4 * q4) - 51 * sqr(q4) - 28 * q2 * q6 + 13 * q8)))
          / N;
      tmp[2]->bin(iy + 1).set(value, sqrt(error));
    }
  }
}

/// @}


/// @name Histograms
/// @{
BinnedProfilePtr<string> _p[2][8];
vector<string> _edges;
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2021_I1917200);

} ```