Rivet analyses

title: BABAR_2008_I791879

$B^-\to \Lambda_c^+\bar{p}^-\pi^-$

Experiment: BABAR (PEP-II)

Inspire ID: 791879

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 78 (2008) 112003

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+-

Measurement of the $\Lambda_c^+\bar{p}^-$ mass distributon in $B^-\to \Lambda_c^+\bar{p}^-\pi^-$ and helicity angle in $B^-\to \Sigma_c^0(\to\Lambda_c^+\pi^-)\bar{p}^-$. Data read from plots in paper but is background subtraced and efficiency corrected.

Source code:BABAR_2008_I791879.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B- -> Lambdac+ pbar pi- class BABAR_2008_I791879 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I791879);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == PID::BPLUS);
  declare(ufs, "UFS");
  DecayedParticles BP(ufs);
  BP.addStable(4122);
  BP.addStable(-4122);
  declare(BP, "BP");
  // histos
  book(_h[0], "TMP/hA", refData(1, 1, 1));
  book(_h[1], 2, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{-4122, 1}, {2212, 1}, {211, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{4122, 1}, {-2212, 1}, {-211, 1}};
  DecayedParticles BP = apply<DecayedParticles>(event, "BP");
  for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
    // select right decay mode
    int sign = 1;
    if (BP.decaying()[ix].pid() > 0 && BP.modeMatches(ix, 3, mode))
      sign = 1;
    else if (BP.decaying()[ix].pid() < 0 && BP.modeMatches(ix, 3, modeCC))
      sign = -1;
    else
      continue;
    const Particle& lam = BP.decayProducts()[ix].at(-4122 * sign)[0];
    const Particle& pp = BP.decayProducts()[ix].at(2212 * sign)[0];
    const Particle& pip = BP.decayProducts()[ix].at(211 * sign)[0];
    _h[0]->fill((lam.momentum() + pp.momentum()).mass());
    if (BP.decaying()[ix].children().size() == 2
        && (BP.decaying()[ix].children()[0].abspid() == 4112
            || BP.decaying()[ix].children()[1].abspid() == 4112)) {
      LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
          BP.decaying()[ix].momentum().betaVec());
      FourMomentum pSigma = boost1.transform(lam.momentum() + pip.momentum());
      Vector3 axis = -pSigma.p3().unit();
      FourMomentum pLambda = boost1.transform(lam.momentum());
      LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pSigma.betaVec());
      _h[1]->fill(axis.dot(boost2.transform(pLambda).p3().unit()));
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // phase space volumes in the different bins (PR has python program which computed these)
  vector<double> phsp = {
      0.1351399774095767,  0.24107906667337267, 0.3088204600383566,  0.36206863378662535,
      0.40659958403332336, 0.4450070368053994,  0.47872719863744506, 0.5086545750109557,
      0.5353906093802568,  0.5593621540798246,  0.5808845790744056,  0.6001982286826937,
      0.6174908272498764,  0.6329119405055217,  0.6465826880700479,  0.6586024850910634,
      0.6690538534165392,  0.67800593732165,    0.685517125504117,   0.6916370414215524,
      0.6964080775759626,  0.6998665941923083,  0.7020438666137178,  0.7029668415116569,
      0.7026587454114315,  0.701139577428797,   0.6984265098419529,  0.6945342141075089,
      0.6894751254590167,  0.6832596558172149,  0.6758963620528058,  0.6673920744258324,
      0.657751988084915,   0.6469797186756903,  0.6350773212151493,  0.6220452692510539,
      0.6078823887065968,  0.5925857373802724,  0.5761504163391165,  0.5585692926468113};
  // normalize the histograms
  for (unsigned int ix = 0; ix < 2; ++ix) normalize(_h[ix], 1., false);
  // convert first plot to scatter and normalize to phase space volume in bin
  // convert to scatter
  Estimate1DPtr tmp;
  book(tmp, 1, 1, 1);
  barchart(_h[0], tmp);
  double step = 0.0344;
  // divide by phase space volume
  for (unsigned int ip = 0; ip < tmp->numBins(); ++ip) tmp->bin(ip + 1).scale(1. / phsp[ip] / step);
}
/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2008_I791879);

} ```