Rivet analyses

title: BABAR_2013_I1272843

Differential branching ratios and $CP$ asymmetries in $B\to X_s\ell^+\ell^-$

Experiment: BABAR (PEP-II)

Inspire ID: 1272843

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 112 (2014) 211802

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+ and B0, originally Upsilon(4S) decay

Differential branching ratios and $CP$ asymmetries in $B\to X_s\ell^+\ell^-$

Source code:BABAR_2013_I1272843.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> Xs l+l- class BABAR_2013_I1272843 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2013_I1272843);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(UnstableParticles(Cuts::abspid == 521 || Cuts::abspid == 511), "UFS");
  // Book histograms
  for (unsigned int ix = 0; ix < 2; ++ix) book(_p_A[ix], 1, 1 + ix, 4);
  for (unsigned int iy = 0; iy < 3; ++iy) {
    book(_h_mX[iy], 2, 1, 1 + iy);
    for (unsigned int ix = 0; ix < 2; ++ix) book(_h_q2[ix][iy], 1, 1 + ix, 1 + iy);
  }
  book(_nBottom, "TMP/BottomCounter");
}

void findDecayProducts(bool& charm,
                       const Particle& mother,
                       unsigned int& nK0,
                       unsigned int& nKp,
                       unsigned int& nKm,
                       Particles& lp,
                       Particles& lm) {
  for (const Particle& p : mother.children()) {
    int id = p.pid();
    if (PID::isCharmHadron(p.pid()))
      charm = true;
    else if (id == PID::POSITRON || id == PID::ANTIMUON)
      lp.push_back(p);
    else if (id == PID::ELECTRON || id == PID::MUON)
      lm.push_back(p);
    else if (id == PID::KPLUS)
      ++nKp;
    else if (id == PID::KMINUS)
      ++nKm;
    else if (id == PID::K0S)
      ++nK0;
    else if (id == PID::PI0 || id == PID::PIPLUS || id == PID::PIMINUS) {
      continue;
    }
    else if (!p.children().empty()) {
      findDecayProducts(charm, p, nK0, nKp, nKm, lp, lm);
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  // Loop over bottoms
  for (const Particle& bottom : apply<UnstableParticles>(event, "UFS").particles()) {
    // remove mixing entries etc
    if (bottom.children()[0].abspid() == bottom.abspid()) continue;
    _nBottom->fill();
    bool charm = false;
    Particles lp, lm;
    unsigned int nK0(0), nKp(0), nKm(0);
    findDecayProducts(charm, bottom, nK0, nKp, nKm, lp, lm);
    if (charm) continue;
    unsigned int nk = nKp - nKm + nK0;
    if (nk % 2 == 0) continue;
    if (lp.size() != 1 || lm.size() != 1 || lp[0].pid() != -lm[0].pid()) continue;
    FourMomentum pl = (lp[0].momentum() + lm[0].momentum());
    FourMomentum pX = bottom.momentum() - pl;
    double q2 = pl.mass2();
    double mX = pX.mass();
    if (lm[0].pid() == 11) {
      _h_q2[0][0]->fill(q2);
      _h_q2[1][0]->fill(q2);
      _h_mX[0]->fill(mX);
    }
    else {
      _h_q2[0][1]->fill(q2);
      _h_q2[1][1]->fill(q2);
      _h_mX[1]->fill(mX);
    }
    _h_q2[0][2]->fill(q2);
    _h_q2[1][2]->fill(q2);
    _h_mX[2]->fill(mX);
    // A_CP doesn't include charmonium regions
    if (q2 < 6.8 || (q2 > 10.1 && q2 < 12.9) || q2 > 14.2) {
      double wgt = bottom.pid() > 0 ? -1 : 1;
      _p_A[0]->fill(q2, wgt);
      _p_A[1]->fill(q2, wgt);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int iy = 0; iy < 3; ++iy) {
    scale(_h_mX[iy], 1e6 / *_nBottom);
    for (unsigned int ix = 0; ix < 2; ++ix) scale(_h_q2[ix][iy], 1e6 / *_nBottom);
  }
}
/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_q2[2][3], _h_mX[3];
Profile1DPtr _p_A[2];
CounterPtr _nBottom;
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2013_I1272843);

} ```