Rivet analyses referenceBELLE_2009_I815978$\gamma\gamma\to \pi^0\pi^0$ for centre-of-mass energies between 0.6 and 4.1 GeVExperiment: BELLE (KEKB) Inspire ID: 815978 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the differential cross section for $\gamma\gamma\to \pi^0\pi^0$ for $0.6 \text{GeV} < W < 4.1 \text{GeV}$. Both the cross section as a function of the centre-of-mass energy of the photonic collision, and the differential cross section with respect to the kaon scattering angle are measured. Source code: BELLE_2009_I815978.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4
5namespace Rivet {
6
7
8 /// @brief gamma gamma -> pi0 pi0
9 class BELLE_2009_I815978 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2009_I815978);
14
15
16 /// @name Analysis methods
17 /// @{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21 // Initialise and register projections
22 declare(FinalState(), "FS");
23 // histos
24 if (inRange(sqrtS()/GeV,0.6,3.3) || inRange(sqrtS()/GeV,3.6,4.1)) {
25 if (sqrtS()>0.72) book(_sigmapipi[0],"TMP/npipi_1",refData(31, 1, 1));
26 book(_sigmapipi[1],"TMP/npipi_2",refData(31, 1, 2));
27 double sMin=0.6, step=0.02;
28 unsigned int ihist=1,iy=1;
29 while (sMin<4.1) {
30 if (inRange(sqrtS()/GeV, sMin, sMin+step)) {
31 break;
32 }
33 sMin+=step;
34 iy+=1;
35 if (iy==4) {
36 ihist+=1;
37 iy=1;
38 }
39 if(fuzzyEquals(1.8, sMin)) step=0.04;
40 else if(fuzzyEquals(2.4, sMin)) step=0.1;
41 else if(fuzzyEquals(3.2, sMin)) sMin=3.6;
42 }
43 if (!inRange(sqrtS()/GeV,3.2,3.6)) book(_h_cTheta,ihist,1,iy);
44 }
45 else {
46 throw Error("Invalid CMS energy for BELLE_2009_I815978");
47 }
48 }
49
50
51 /// Perform the per-event analysis
52 void analyze(const Event& event) {
53 Particles part = apply<FinalState>(event,"FS").particles();
54 if (part.size()!=2) vetoEvent;
55 for (const Particle & p : part) {
56 if (p.pid()!=PID::PI0) vetoEvent;
57 }
58 double cTheta = abs(part[0].mom().z()/part[0].mom().p3().mod());
59 if (cTheta<=0.6&&_sigmapipi[0]) _sigmapipi[0]->fill(sqrtS());
60 if (cTheta<=0.8&&_sigmapipi[1]) _sigmapipi[1]->fill(sqrtS());
61 if (_h_cTheta ) _h_cTheta ->fill(cTheta);
62 }
63
64
65 /// Normalise histograms etc., after the run
66 void finalize() {
67 double fact = crossSection()/nanobarn/sumOfWeights();
68 if (_h_cTheta ) scale(_h_cTheta ,fact);
69 for (unsigned int ix=0; ix<2; ++ix) {
70 if (!_sigmapipi[ix]) continue;
71 scale(_sigmapipi[ix],fact);
72 Estimate1DPtr tmp;
73 book(tmp, 31, 1, 1+ix);
74 barchart(_sigmapipi[ix],tmp);
75 }
76 }
77
78 /// @}
79
80
81 /// @name Histograms
82 /// @{
83 Histo1DPtr _sigmapipi[2],_h_cTheta;
84 /// @}
85
86
87 };
88
89
90 RIVET_DECLARE_PLUGIN(BELLE_2009_I815978);
91
92}
|