1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief chi_c at 7 TeV
 9  class LHCB_2012_I1087907 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2012_I1087907);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      declare(UnstableParticles(), "UFS");
22      for(unsigned int ichi=0;ichi<2;++ichi) {
23	book(_h_chi[ichi],"TMP/h_CHI_"+toString(ichi),refData(1,1,1));
24      }
25    }
26
27
28    /// Perform the per-event analysis
29    void analyze(const Event& event) {
30
31      // Final state of unstable particles to get particle spectra
32      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
33
34      for (const Particle& p : ufs.particles(Cuts::pid==20443 ||
35					     Cuts::pid==445)) {
36	// prompt
37	if(p.fromBottom()) continue;
38	// J/psi /gamma mode
39	if(p.children().size()!=2) continue;
40	Particle Jpsi;
41	if(p.children()[0].pid()==22 && p.children()[1].pid()==443) {
42	  Jpsi=p.children()[1];
43	}
44	else if(p.children()[1].pid()==22 && p.children()[0].pid()==443) {
45	  Jpsi=p.children()[0];
46	}
47	else
48	  continue;
49	double absrap=Jpsi.absrap();
50	if(absrap<2. || absrap>4.5) continue;
51	unsigned int ichi = p.pid()==20443 ? 0 : 1;
52	double xp=Jpsi.perp();
53	_h_chi[ichi]->fill(xp);
54      }
55    }
56
57
58    /// Normalise histograms etc., after the run
59    void finalize() {
60      // chi_c to gamma J/psi branching ratios from PDG 2021
61      vector<double> br = {0.343,0.190};
62      Estimate1DPtr tmp;
63      book(tmp,1,1,1);
64      divide(_h_chi[1],_h_chi[0],tmp);
65      tmp->scale(br[1]/br[0]);
66    }
67
68    /// @}
69
70
71    /// @name Histograms
72    /// @{
73    Histo1DPtr _h_chi[2];
74    /// @}
75
76
77  };
78
79
80  RIVET_DECLARE_PLUGIN(LHCB_2012_I1087907);
81
82}