1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4#include "Rivet/Projections/DecayedParticles.hh"
 5
 6namespace Rivet {
 7
 8
 9  /// @brief B_c -> J/psi pi+pi0
10  class LHCB_2024_I2756705 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2024_I2756705);
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      UnstableParticles ufs = UnstableParticles(Cuts::abspid==541);
22      declare(ufs, "UFS");
23      DecayedParticles BC(ufs);
24      BC.addStable( PID::PI0);
25      BC.addStable( PID::JPSI);
26      declare(BC, "BC");
27      book(_h,1,1,1);
28    }
29
30
31    /// Perform the per-event analysis
32    void analyze(const Event& event) {
33      static const map<PdgId,unsigned int> & mode   = { { 443,1}, { 211,1}, { 111,1} };
34      static const map<PdgId,unsigned int> & modeCC = { { 443,1}, {-211,1}, { 111,1} };
35      DecayedParticles BC = apply<DecayedParticles>(event, "BC");
36      // loop over particles
37      for(unsigned int ix=0;ix<BC.decaying().size();++ix) {
38	int sign = BC.decaying()[ix].pid()/BC.decaying()[ix].abspid();
39	if ((sign== 1 && BC.modeMatches(ix,3,mode  )) ||
40	    (sign==-1 && BC.modeMatches(ix,3,modeCC))) {
41	  const Particle & pi0 = BC.decayProducts()[ix].at(      111)[0];
42	  const Particle & pip = BC.decayProducts()[ix].at( sign*211)[0];
43	  FourMomentum ptotal=pi0.momentum()+pip.momentum();
44          _h->fill(ptotal.mass());
45        }
46      }
47    }
48
49
50    /// Normalise histograms etc., after the run
51    void finalize() {
52      normalize(_h,1.,false);
53    }
54
55    /// @}
56
57    /// @name Histograms
58    /// @{
59    Histo1DPtr _h;
60    /// @}
61
62  };
63
64
65  RIVET_DECLARE_PLUGIN(LHCB_2024_I2756705);
66
67}