|
Rivet analyses reference
ZEUS_1999_I470499
Forward jet production in deep inelastic scattering at HERA (ZEUS)
Experiment: ZEUS (HERA)
Inspire ID: 470499
Status: VALIDATED
Authors:
References:
Beams: e+ p+, p+ e+
Beam energies: (27.5, 820.0); (820.0, 27.5) GeV
The inclusive forward jet cross section in deep inelastic e+p scattering has been measured in the region of x-Bjorken, $4.5 \times 10^{-4}$ to $4.5 \times 10^{-2}$. This measurement is motivated by the search for effects of BFKL-like parton shower evolution. The cross section at hadron level as a function of x is compared to cross sections predicted by various Monte Carlo models. An excess of forward jet production at small x is observed, which is not reproduced by models based on DGLAP parton shower evolution.
Source code:
ZEUS_1999_I470499.cc
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/DISKinematics.hh"
#include "fastjet/SISConePlugin.hh"
#include<cmath>
namespace Rivet {
/// @brief Forward jet production in deep inelastic scattering at HERA (ZEUS)
class ZEUS_1999_I470499 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ZEUS_1999_I470499);
/// @name Analysis methods
///@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
// The basic final-state projection:
// all final-state particles within
// the given eta acceptance
const FinalState fs; /// SHOULD I KEEP THIS AT ALL?
declare(fs, "FS");
// declare jets
double jet_radius = 1.0;///FIGURE THIS OUT
declare(FastJets(fs, FastJets::PXCONE, jet_radius), "Jets");//FIGURE THE JET OUT
// declare DIS Kinematics
declare(DISLepton(), "Lepton");
declare(DISKinematics(), "Kinematics");
// take binning from reference data using HEPData ID (digits in "d01-x01-y01" etc.)
book(_h["xbj"], 1, 1, 1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Retrieve dressed leptons, sorted by pT
const FinalState& fs = apply<FinalState>(event, "FS");
const size_t numParticles = fs.particles().size();
if (numParticles < 2) {
MSG_DEBUG("Failed leptonic event cut");
vetoEvent;
}
const DISKinematics& dk = applyProjection<DISKinematics>(event, "Kinematics");
const DISLepton& dl = applyProjection<DISLepton>(event,"Lepton");
// Get the DIS kinematics
double xbj = dk.x();
double ybj = dk.y();
double Q2 = dk.Q2()/GeV;
//cut on y
if (ybj<0.1) vetoEvent;
if (4.5*pow(10,-4)>xbj && xbj>4.5*pow(10,-2)) vetoEvent;
//Frame transfer
const LorentzTransform breitboost = dk.boostBreit();
//on scattered lepton
FourMomentum leptonMom = dl.out().momentum();
double enel = leptonMom.E();
bool cut = enel>10*GeV;
if (!cut) vetoEvent;
//scattered jets
const Jets jets = apply<FastJets>(event, "Jets").jets(Cuts::Et > 5*GeV && Cuts::eta<2.6, cmpMomByEt);
//Cuts::pz/(820*GeV)>0.036
//&& Cuts::0.5<pow(Et,2)/Q2<2 && Cuts::breMom.pz>0
bool loopjet=false;
for (const Jet&j:jets){
//cout << " j.pz " << j.pz()/(820*GeV) << endl;
if (j.pz()/(820*GeV)<0.036) continue;
// cout << pow(j.Et(),2) << endl;
if (0.5>pow(j.Et(),2)/Q2||pow(j.Et(),2)/Q2>2) continue;
FourMomentum breMom = breitboost.transform(j.momentum());
//cout<< " pz " << breMom.pz() << endl;
if (breMom.pz()<0) continue;
loopjet=true;
}
// cout<< " loojet " << loopjet << endl;
if(loopjet) _h["xbj"]->fill(xbj);
// Fill histogram with leading b-jet pT
}
/// Normalise histograms etc., after the run
void finalize() {
scale(_h["xbj"], crossSection()/nanobarn/sumW());
//normalize(_h["xbj"]);
}
///@}
/// @name Histograms
///@{
map<string, Histo1DPtr> _h;
map<string, Profile1DPtr> _p;
map<string, CounterPtr> _c;
///@}
};
RIVET_DECLARE_PLUGIN(ZEUS_1999_I470499);
}
|
|