Rivet analyses referencePLUTO_1984_I204487$\gamma\gamma\to\pi^+\pi^-$ for centre-of-mass energies between 0.36 and 1.72 GeVExperiment: PLUTO (PETRA) Inspire ID: 204487 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the differential cross section for $\gamma\gamma\to\pi^+\pi^-$. The cross section as a function of the centre-of-mass energy of the photonic collision is measured. Source code: PLUTO_1984_I204487.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4
5namespace Rivet {
6
7
8 /// @brief gamma gamma -> pi+pi-
9 class PLUTO_1984_I204487 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(PLUTO_1984_I204487);
14
15
16 /// @name Analysis methods
17 ///@{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21 // Final state
22 declare(FinalState(),"FS");
23 // check CMS energy in range
24 if(sqrtS()<0.36*GeV || sqrtS()>1.72*GeV)
25 throw Error("Invalid CMS energy for PLUTO_1984_I1260740");
26 book(_cPi, "/TMP/nPi");
27 }
28
29
30 /// Perform the per-event analysis
31 void analyze(const Event& event) {
32 Particles part = applyProjection<FinalState>(event,"FS").particles();
33 if(part.size()!=2) vetoEvent;
34 double cTheta(0.);
35 bool foundP(false),foundM(false);
36 for(const Particle & p : part) {
37 if(p.pid()==PID::PIPLUS) {
38 foundP=true;
39 cTheta = abs(p.momentum().z()/p.momentum().p3().mod());
40 }
41 else if(p.pid()==PID::PIMINUS)
42 foundM=true;
43 }
44 if(!foundP || !foundM) vetoEvent;
45 if(cTheta<=0.2) _cPi->fill();
46 }
47
48
49 /// Normalise histograms etc., after the run
50 void finalize() {
51 double fact = crossSection()/nanobarn/sumOfWeights();
52 double sigma = _cPi->val()*fact/0.2;
53 double error = _cPi->err()*fact/0.2;
54 Scatter2D temphisto(refData(1, 1, 1));
55 Scatter2DPtr mult;
56 book(mult, 1, 1, 1);
57 for (size_t b = 0; b < temphisto.numPoints(); b++) {
58 const double x = temphisto.point(b).x();
59 pair<double,double> ex = temphisto.point(b).xErrs();
60 pair<double,double> ex2 = ex;
61 if(ex2.first ==0.) ex2. first=0.0001;
62 if(ex2.second==0.) ex2.second=0.0001;
63 if (inRange(sqrtS(), x-ex2.first, x+ex2.second)) {
64 mult->addPoint(x, sigma, ex, make_pair(error,error));
65 }
66 else {
67 mult->addPoint(x, 0., ex, make_pair(0.,.0));
68 }
69 }
70 }
71
72 ///@}
73
74
75 /// @name Histograms
76 ///@{
77 CounterPtr _cPi;
78 ///@}
79
80
81 };
82
83
84 RIVET_DECLARE_PLUGIN(PLUTO_1984_I204487);
85
86}
|