Rivet analyses referenceOPAL_1998_I470419Photon and Light Meson Production in Hadronic $Z^0$ DecaysExperiment: OPAL (LEP 1) Inspire ID: 470419 Status: VALIDATED Authors:
Beam energies: (45.6, 45.6) GeV Run details:
The inclusive production rates and differential cross sections of photons and mesons with a final state containing photons have been measured with the OPAL detector at LEP. The light mesons covered by the measurements are the $\pi^0$, $\eta$, $\rho(770)^\pm$, $\omega(782)$, $\eta'(958)$ and $a_0(980)^\pm$. Source code: OPAL_1998_I470419.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/Beam.hh"
4#include "Rivet/Projections/FinalState.hh"
5#include "Rivet/Projections/ChargedFinalState.hh"
6#include "Rivet/Projections/UnstableParticles.hh"
7
8namespace Rivet {
9
10
11 /// @brief OPAL photon/light meson paper
12 ///
13 /// @author Peter Richardson
14 class OPAL_1998_I470419 : public Analysis {
15 public:
16
17 RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_1998_I470419);
18
19
20 /// @name Analysis methods
21 /// @{
22
23 void init() {
24 declare(Beam(), "Beams");
25 declare(ChargedFinalState(), "FS");
26 declare(UnstableParticles(), "UFS");
27 book(_histXePhoton , 2, 1, 1);
28 book(_histXiPhoton , 3, 1, 1);
29 book(_histXePi , 4, 1, 1);
30 book(_histXiPi , 5, 1, 1);
31 book(_histXeEta , 6, 1, 1);
32 book(_histXiEta , 7, 1, 1);
33 book(_histXeRho , 8, 1, 1);
34 book(_histXiRho , 9, 1, 1);
35 book(_histXeOmega ,10, 1, 1);
36 book(_histXiOmega ,11, 1, 1);
37 book(_histXeEtaPrime ,12, 1, 1);
38 book(_histXiEtaPrime ,13, 1, 1);
39 book(_histXeA0 ,14, 1, 1);
40 book(_histXiA0 ,15, 1, 1);
41 }
42
43
44 void analyze(const Event& e) {
45 // First, veto on leptonic events by requiring at least 4 charged FS particles
46 const FinalState& fs = apply<FinalState>(e, "FS");
47 const size_t numParticles = fs.particles().size();
48
49 // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
50 if (numParticles < 2) {
51 MSG_DEBUG("Failed leptonic event cut");
52 vetoEvent;
53 }
54 MSG_DEBUG("Passed leptonic event cut");
55
56 // Get beams and average beam momentum
57 const ParticlePair& beams = apply<Beam>(e, "Beams").beams();
58 const double meanBeamMom = ( beams.first.p3().mod() +
59 beams.second.p3().mod() ) / 2.0;
60 MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
61
62 // Final state of unstable particles to get particle spectra
63 const UnstableParticles& ufs = apply<UnstableParticles>(e, "UFS");
64
65 for (const Particle& p : ufs.particles()) {
66 const int id = p.abspid();
67 double xi = -log(p.p3().mod()/meanBeamMom);
68 double xE = p.E()/meanBeamMom;
69 switch (id) {
70 case 22: // Photons
71 _histXePhoton->fill(xE);
72 _histXiPhoton->fill(xi);
73 break;
74 case 111: // Neutral pions
75 _histXePi->fill(xE);
76 _histXiPi->fill(xi);
77 break;
78 case 221: // eta
79 _histXeEta->fill(xE);
80 _histXiEta->fill(xi);
81 break;
82 case 213: // Charged rho (770)
83 _histXeRho->fill(xE);
84 _histXiRho->fill(xi);
85 break;
86 case 223: // omega (782)
87 _histXeOmega->fill(xE);
88 _histXiOmega->fill(xi);
89 break;
90 case 331: // eta' (958)
91 _histXeEtaPrime->fill(xE);
92 _histXiEtaPrime->fill(xi);
93 break;
94 case 9000211: // Charged a_0 (980)
95 _histXeA0->fill(xE);
96 _histXiA0->fill(xi);
97 break;
98 }
99 }
100 }
101
102
103 /// Finalize
104 void finalize() {
105 scale(_histXePhoton , 1./sumOfWeights());
106 scale(_histXiPhoton , 1./sumOfWeights());
107 scale(_histXePi , 1./sumOfWeights());
108 scale(_histXiPi , 1./sumOfWeights());
109 scale(_histXeEta , 1./sumOfWeights());
110 scale(_histXiEta , 1./sumOfWeights());
111 scale(_histXeRho , 1./sumOfWeights());
112 scale(_histXiRho , 1./sumOfWeights());
113 scale(_histXeOmega , 1./sumOfWeights());
114 scale(_histXiOmega , 1./sumOfWeights());
115 scale(_histXeEtaPrime, 1./sumOfWeights());
116 scale(_histXiEtaPrime, 1./sumOfWeights());
117 scale(_histXeA0 , 1./sumOfWeights());
118 scale(_histXiA0 , 1./sumOfWeights());
119 }
120
121 /// @}
122
123
124 private:
125
126 /// @{
127 Histo1DPtr _histXePhoton;
128 Histo1DPtr _histXiPhoton;
129 Histo1DPtr _histXePi;
130 Histo1DPtr _histXiPi;
131 Histo1DPtr _histXeEta;
132 Histo1DPtr _histXiEta;
133 Histo1DPtr _histXeRho;
134 Histo1DPtr _histXiRho;
135 Histo1DPtr _histXeOmega;
136 Histo1DPtr _histXiOmega;
137 Histo1DPtr _histXeEtaPrime;
138 Histo1DPtr _histXiEtaPrime;
139 Histo1DPtr _histXeA0;
140 Histo1DPtr _histXiA0;
141 /// @}
142
143 };
144
145
146
147 RIVET_DECLARE_ALIASED_PLUGIN(OPAL_1998_I470419, OPAL_1998_S3749908);
148
149}
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