1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/Beam.hh"
 4#include "Rivet/Projections/UnstableParticles.hh"
 5
 6namespace Rivet {
 7
 8
 9  /// @brief Excited Lambda_c spectra
10  class ARGUS_1997_I440304 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1997_I440304);
15
16
17    /// @name Analysis methods
18    /// @{
19
20    /// Book histograms and initialise projections before the run
21    void init() {
22      // projections
23      declare(Beam(), "Beams");
24      declare(UnstableParticles(), "UFS");
25      // book histos
26      book(_h_rate1,1,1,1);
27      book(_h_rate2,1,2,1);
28      book(_h_x,2,1,1);
29    }
30
31
32    void findDecayProducts(Particle parent, Particles & Lambda_c, Particles & pions,unsigned int & nstable) {
33      for(const Particle & p : parent.children()) {
34	if(p.abspid()==4122) {
35	  Lambda_c.push_back(p);
36	  ++nstable;
37	}
38	else if(p.abspid()==PID::PIPLUS) {
39	  pions.push_back(p);
40	  ++nstable;
41	}
42	else if(!p.children().empty())
43	  findDecayProducts(p,Lambda_c,pions,nstable);
44	else
45	  ++nstable;
46      }
47    }
48
49    /// Perform the per-event analysis
50    void analyze(const Event& event) {
51      static const int id2595 = 14122;
52      // Get beams and average beam momentum
53      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
54      const double Emax = ( beams.first.p3().mod() + beams.second.p3().mod() ) / 2.0;
55      const double Pmax = sqrt(sqr(Emax)-sqr(2.595));
56      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
57      for (const Particle& p : ufs.particles(Cuts::abspid==id2595)) {
58	// spectrum
59	double xp = p.momentum().p3().mod()/Pmax;
60	_h_x->fill(xp);
61	Particles Lambda_c,pions;
62	unsigned int nstable(0);
63	findDecayProducts(p,Lambda_c,pions,nstable);
64	if(nstable==3&&pions.size()==2&&Lambda_c.size()==1) {
65	  _h_rate1->fill(xp);
66	  _h_rate2->fill(xp);
67	}
68      }
69    }
70
71
72    /// Normalise histograms etc., after the run
73    void finalize() {
74      normalize(_h_x);
75      // br for lambda_c mode from pdg 2018
76      double br = 0.0623;
77      scale(_h_rate1,0.3*br*crossSection()/sumOfWeights()/picobarn);
78      scale(_h_rate2,    br*crossSection()/sumOfWeights()/picobarn);
79    }
80
81    /// @}
82
83
84    /// @name Histograms
85    /// @{
86    Histo1DPtr _h_x,_h_rate1,_h_rate2;
87    /// @}
88
89
90  };
91
92
93  RIVET_DECLARE_PLUGIN(ARGUS_1997_I440304);
94
95}