Rivet analyses referenceZEUS_2000_I524911Measurement of azimuthal asymmetries in deep inelastic scatteringExperiment: ZEUS (HERA) Inspire ID: 524911 Status: VALIDATED Authors:
Beam energies: (820.0, 27.5); (27.5, 820.0) GeV Run details:
The distribution of the azimuthal angle for the charged hadrons has been studied in the hadronic centre-of-mass system for neutral current deep inelastic positron-proton scattering with the ZEUS detector at HERA. Measurements of the dependence of the moments of this distribution on the transverse momenta of the charged hadrons are presented. Source code: ZEUS_2000_I524911.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FastJets.hh"
4#include "Rivet/Projections/DISKinematics.hh"
5#include "Rivet/Projections/DISLepton.hh"
6#include "Rivet/Projections/ChargedFinalState.hh"
7
8namespace Rivet {
9
10
11 /// @brief Measurement of azimuthal asymmetries in deep inelastic scattering (ZEUS)
12 class ZEUS_2000_I524911 : public Analysis {
13 public:
14
15 /// Constructor
16 DEFAULT_RIVET_ANALYSIS_CTOR(ZEUS_2000_I524911);
17
18
19 /// @name Analysis methods
20 ///@{
21
22 /// Book histograms and initialise projections before the run
23 void init() {
24
25 // Initialise and register projections
26 declare(DISLepton(), "Lepton");
27 declare(DISKinematics(), "Kinematics");
28
29 // The basic final-state projection:
30 // all final-state particles within
31 // the given eta acceptance
32
33 const ChargedFinalState cfs;
34 declare(cfs, "CFS");
35
36 book(_h["A1"], 1, 1, 1);
37 book(_h["A2"], 1, 1, 2);
38 book(_h["A3"], 1, 1, 3);
39 book(_h["A4"], 1, 1, 4);
40
41 book(_p["cosphi"],2, 1, 1) ;
42 book(_p["cos2phi"],2, 1, 2) ;
43
44// counter pointer to store the no. of events
45 book(_Nevt_after_cuts, "TMP/Nevt_after_cuts");
46
47
48
49 }
50
51
52 /// Perform the per-event analysis
53 void analyze(const Event& event) {
54
55 //const FinalState& fsall = apply<FinalState>(event, "FS");
56 const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
57
58 const DISKinematics& dk = applyProjection<DISKinematics>(event, "Kinematics");
59 const DISLepton& dl = applyProjection<DISLepton>(event,"Lepton");
60
61 double x = dk.x();
62 double y = dk.y();
63 const double Q2 = dk.Q2();
64
65 double PT[] = { 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0};
66 // Extract the particles other than the lepton
67
68 if(x<0.01||x>0.1) vetoEvent;
69 if(y<0.2||y>0.8) vetoEvent;
70 if(Q2 > 7220 || Q2 < 180) vetoEvent;
71
72 _Nevt_after_cuts -> fill();
73
74 Particles particles;
75 particles.reserve(cfs.particles().size());
76
77 ConstGenParticlePtr dislepGP = dl.out().genParticle();
78 for (const Particle& p : cfs.particles()) {
79 ConstGenParticlePtr loopGP = p.genParticle();
80
81 if (loopGP == dislepGP) continue;
82 particles.push_back(p);
83 }
84
85 const LorentzTransform hcmboost = dk.boostHCM();
86 for (size_t ip1 = 0; ip1 < particles.size(); ++ip1) {
87 const Particle& p = particles[ip1];
88
89 // calculate zh
90 double zh = 2.*x/Q2* (dk.beamHadron().E()*p.momentum().E() - dk.beamHadron().pz()*p.momentum().pz()) ;
91 // cout << " zh " << zh << endl;
92 // Boost to hcm
93
94 if (zh < 0.2 ) continue ;
95
96 const FourMomentum hcmMom = hcmboost.transform(p.momentum());
97
98 const double phi =mapAngleMPiToPi(hcmMom.phi())/degree ;
99
100
101
102// Filling histograms with values of cos(phi) and cos(2phi) wrt the corresponding momentum cuts
103
104 for (size_t i = 0; i < 8; ++i) {
105 if(hcmMom.pT() > PT[i] ) {
106 _p["cosphi"]->fill(i+1,cos(hcmMom.phi()));
107 _p["cos2phi"]->fill(i+1,cos(2.*hcmMom.phi()));
108 }
109 }
110
111
112
113 if(hcmMom.pT() > PT[1] ) { _h["A1"] -> fill(phi); }
114
115 if(hcmMom.pT() > PT[3] ) { _h["A2"] -> fill(phi); }
116
117 if(hcmMom.pT() > PT[5] ) { _h["A3"] -> fill(phi); }
118
119 if(hcmMom.pT() > PT[7] ) { _h["A4"] -> fill(phi); }
120
121 }
122
123
124 }
125
126
127
128 /// Normalise histograms etc., after the run
129 void finalize() {
130
131 // correct binwidth in degree to correct for binning from degree to rad by: binwidth/(2PI/10.)
132 double norm = dbl(*_Nevt_after_cuts) ;
133 // cout << " Nev " << norm << " bin_width= " <<_h["A2"]->bin(0).xWidth() << endl;
134 double degTOrad_width = _h["A1"]->bin(0).xWidth()*10./2./M_PI ;
135 if (norm > 1 ) {
136 scale(_h["A1"], degTOrad_width/norm);
137 scale(_h["A2"], degTOrad_width/norm);
138 scale(_h["A3"], degTOrad_width/norm);
139 scale(_h["A4"], degTOrad_width/norm);
140 }
141
142 }
143
144 ///@}
145
146
147 /// @name Histograms
148 ///@{
149 map<string, Histo1DPtr> _h;
150 map<string, Profile1DPtr> _p;
151 map<string, CounterPtr> _c;
152 CounterPtr _Nevt_after_cuts;
153 ///@}
154
155
156
157 };
158
159
160 DECLARE_RIVET_PLUGIN(ZEUS_2000_I524911);
161
162}
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