1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4
  5namespace Rivet {
  6
  7
  8  /// @brief M_x in B -> eta' Xs
  9  class BABAR_2004_I642355 : public Analysis {
 10  public:
 11
 12    /// Constructor
 13    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2004_I642355);
 14
 15
 16    /// @name Analysis methods
 17    ///@{
 18
 19    /// Book histograms and initialise projections before the run
 20    void init() {
 21      // projections
 22      declare(UnstableParticles(),"UFS");
 23      // histograms
 24      book(_w_ups4,"/TMP/w_ups4");
 25      book(_h_X,1,1,1);
 26    }
 27
 28    void findDecay(Particle parent, bool & charm, Particles & etaP, Particles & pi0,
 29		   Particles & pip, Particles & Kp, Particles & K0) {
 30      for(const Particle & p : parent.children()) {
 31	if(isCharm(p)) {
 32	  charm = true;
 33	  return;
 34	}
 35	else if(p.pid()==PID::ETAPRIME) {
 36	  etaP.push_back(p);
 37	}
 38	else if(p.abspid()==PID::PIPLUS) {
 39	  pip.push_back(p);
 40	}
 41	else if(p.abspid()==PID::KPLUS) {
 42	  Kp.push_back(p);
 43	}
 44	else if(p.pid()==PID::PI0) {
 45	  pi0.push_back(p);
 46	}
 47	else if(p.pid()==PID::K0S) {
 48	  K0.push_back(p);
 49	}
 50	else if(!p.children().empty()) {
 51	  findDecay(p,charm,etaP,pi0,pip,Kp,K0); 
 52	}
 53      }
 54    }
 55
 56    /// Perform the per-event analysis
 57    void analyze(const Event& event) {
 58      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
 59      for(const Particle & p : ufs.particles(Cuts::pid==300553)) {
 60	_w_ups4->fill();
 61        const LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.mom().betaVec());
 62	for(const Particle & B:p.children()) {
 63	  if(B.abspid()!=511 && B.abspid()!=521) continue;
 64	  // find the decay
 65	  bool charm=false;
 66	  Particles etaP, pi0, pip, Kp, K0;
 67	  findDecay(B,charm,etaP,pi0,pip,Kp,K0);
 68	  if(charm || etaP.size()!=1 ) continue;
 69	  if(Kp.empty()&&Kp.empty()) continue;
 70	  double pEta = boost.transform(etaP[0].momentum()).p3().mod();
 71	  if(pEta<2. || pEta>2.7) continue;
 72	  // four momentum of the Xs system
 73	  FourMomentum pX;
 74	  if(K0.size()==1)
 75	    pX+= K0[0].momentum();
 76	  else if(Kp.size()==1)
 77	    pX+= Kp[0].momentum();
 78	  else
 79	    continue;
 80	  for(const Particle & pi : pip)
 81	    pX+=pi.momentum();
 82	  if(pi0.size()==1)
 83	    pX+=pi0[0].momentum();
 84	  _h_X->fill(pX.mass());
 85	  
 86	}
 87      }
 88    }
 89
 90
 91    /// Normalise histograms etc., after the run
 92    void finalize() {
 93      scale(_h_X, 0.5/ *_w_ups4);
 94    }
 95
 96    ///@}
 97
 98
 99    /// @name Histograms
100    ///@{
101    CounterPtr _w_ups4;
102    Histo1DPtr _h_X;
103    ///@}
104
105
106  };
107
108
109  RIVET_DECLARE_PLUGIN(BABAR_2004_I642355);
110
111}