Rivet analyses

Measurement of the mass mX produced in B → η′Xs

Experiment: BABAR (PEP-II)

Inspire ID: 642355

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 93 (2004) 061801

Beams: * *

Beam energies: ANY

Run details: - Any process producing Upsilon(4S), originally e+e-

Measurement of the mass mX produced in B → η′Xs where the η′ meson has momentum 2 < p < 2.7 GeV in the Υ(4S) rest frame.

Source code:BABAR_2004_I642355.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief M_x in B -> eta' Xs
  class BABAR_2004_I642355 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2004_I642355);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(),"UFS");
      // histograms
      book(_w_ups4,"/TMP/w_ups4");
      book(_h_X,1,1,1);
    }

    void findDecay(Particle parent, bool & charm, Particles & etaP, Particles & pi0,
           Particles & pip, Particles & Kp, Particles & K0) {
      for(const Particle & p : parent.children()) {
    if(isCharm(p)) {
      charm = true;
      return;
    }
    else if(p.pid()==PID::ETAPRIME) {
      etaP.push_back(p);
    }
    else if(p.abspid()==PID::PIPLUS) {
      pip.push_back(p);
    }
    else if(p.abspid()==PID::KPLUS) {
      Kp.push_back(p);
    }
    else if(p.pid()==PID::PI0) {
      pi0.push_back(p);
    }
    else if(p.pid()==PID::K0S) {
      K0.push_back(p);
    }
    else if(!p.children().empty()) {
      findDecay(p,charm,etaP,pi0,pip,Kp,K0);
    }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for(const Particle & p : ufs.particles(Cuts::pid==300553)) {
    _w_ups4->fill();
        const LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.mom().betaVec());
    for(const Particle & B:p.children()) {
      if(B.abspid()!=511 && B.abspid()!=521) continue;
      // find the decay
      bool charm=false;
      Particles etaP, pi0, pip, Kp, K0;
      findDecay(B,charm,etaP,pi0,pip,Kp,K0);
      if(charm || etaP.size()!=1 ) continue;
      if(Kp.empty()&&Kp.empty()) continue;
      double pEta = boost.transform(etaP[0].momentum()).p3().mod();
      if(pEta<2. || pEta>2.7) continue;
      // four momentum of the Xs system
      FourMomentum pX;
      if(K0.size()==1)
        pX+= K0[0].momentum();
      else if(Kp.size()==1)
        pX+= Kp[0].momentum();
      else
        continue;
      for(const Particle & pi : pip)
        pX+=pi.momentum();
      if(pi0.size()==1)
        pX+=pi0[0].momentum();
      _h_X->fill(pX.mass());

    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_X, 0.5/ *_w_ups4);
    }

    /// @}


    /// @name Histograms
    /// @{
    CounterPtr _w_ups4;
    Histo1DPtr _h_X;
    /// @}


  };


  RIVET_DECLARE_PLUGIN(BABAR_2004_I642355);

}