Rivet analyses referenceSTAR_2009_UE_HELENUE measurement in $pp$ at 200 GeVExperiment: STAR (RHIC) Spires ID: None Status: PRELIMINARY Authors:
Beam energies: (100.0, 100.0) GeV Run details:
WARNING! Mark as "STAR preliminary" and contact authors when using this! UE analysis similar to Rick Field's leading jet analysis. SIScone with radius/resolution parameter R=0.7 is used. Particles with $pT > 0.2 \text{GeV}$ and $|\eta| < 1$ are included in the analysis. All particles are assumed to have zero mass. Only jets with neutral energy $< 0.7$ are included. For the transMIN and transMAX $\Delta(\phi)$ is between $\pi/3$ and $2\pi/3$, and $\Delta(\eta) < 2.0$. For the jet region the area of the jet is used for the normalization, i.e. the scaling factor is $\pi R^2$ and not $\mathrm{d}\phi\mathrm{d}\eta$ (this is different from what Rick Field does!). The tracking efficiency is $\sim 0.8$, but that is an approximation, as below $pT \sim 0.6 \text{GeV}$ it is falling quite steeply. Source code: STAR_2009_UE_HELEN.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/ChargedFinalState.hh"
4#include "Rivet/Projections/NeutralFinalState.hh"
5#include "Rivet/Projections/MergedFinalState.hh"
6#include "Rivet/Projections/VetoedFinalState.hh"
7#include "Rivet/Projections/FastJets.hh"
8#include "fastjet/SISConePlugin.hh"
9
10namespace Rivet {
11
12
13 /// @brief STAR underlying event
14 ///
15 /// @author Hendrik Hoeth
16 class STAR_2009_UE_HELEN : public Analysis {
17 public:
18
19 /// Constructor
20 RIVET_DEFAULT_ANALYSIS_CTOR(STAR_2009_UE_HELEN);
21
22
23 /// @name Analysis methods
24 /// @{
25
26 void init() {
27 // Charged final state, |eta|<1, pT>0.2GeV
28 const Cut c = Cuts::abseta < 1.0 && Cuts::pT >= 0.2*GeV;
29
30 const ChargedFinalState cfs(c);
31 declare(cfs, "CFS");
32
33 // Neutral final state, |eta|<1, ET>0.2GeV (needed for the jets)
34 const NeutralFinalState nfs(c);
35 declare(nfs, "NFS");
36
37 // STAR can't see neutrons and K^0_L
38 VetoedFinalState vfs(nfs);
39 vfs.vetoNeutrinos();
40 vfs.addVetoPairId(PID::K0L);
41 vfs.addVetoPairId(PID::NEUTRON);
42 declare(vfs, "VFS");
43
44 // Jets are reconstructed from charged and neutral particles,
45 // and the cuts are different (pT vs. ET), so we need to merge them.
46 const MergedFinalState jfs(cfs, vfs);
47 declare(jfs, "JFS");
48
49 // SISCone, R = 0.7, overlap_threshold = 0.75
50 declare(FastJets(jfs, JetAlg::SISCONE, 0.7), "AllJets");
51
52 // Book histograms
53 book(_hist_pmaxnchg, 1, 1, 1);
54 book(_hist_pminnchg, 2, 1, 1);
55 book(_hist_anchg, 3, 1, 1);
56 }
57
58
59 // Do the analysis
60 void analyze(const Event& e) {
61 const FinalState& cfs = apply<ChargedFinalState>(e, "CFS");
62 if (cfs.particles().size() < 1) {
63 MSG_DEBUG("Failed multiplicity cut");
64 vetoEvent;
65 }
66
67 const Jets& alljets = apply<FastJets>(e, "AllJets").jetsByPt();
68 MSG_DEBUG("Total jet multiplicity = " << alljets.size());
69
70 // The jet acceptance region is |eta|<(1-R)=0.3 (with R = jet radius)
71 // Jets also must have a neutral energy fraction of < 0.7
72 Jets jets;
73 for (const Jet& jet : alljets) {
74 if (jet.neutralEnergy()/jet.totalEnergy() < 0.7 && jet.abseta() < 0.3) {
75 jets.push_back(jet);
76 }
77 }
78
79 // This analysis requires a di-jet like event.
80 // WARNING: There is more data in preparation, some of which
81 // does _not_ have this constraint!
82 if (jets.size() != 2) {
83 MSG_DEBUG("Failed jet multiplicity cut");
84 vetoEvent;
85 }
86
87 // The di-jet constraints in this analysis are:
88 // - 2 and only 2 jets in the acceptance region
89 // - delta(Phi) between the jets is > 150 degrees
90 // - Pt_awayjet/Pt_towards_jet > 0.7
91 if (deltaPhi(jets[0].phi(), jets[1].phi()) <= 5*PI/6 ||
92 jets[1].pT()/jets[0].pT() <= 0.7)
93 {
94 MSG_DEBUG("Failed di-jet criteria");
95 vetoEvent;
96 }
97
98 // Now lets start ...
99 const double jetphi = jets[0].phi();
100 const double jetpT = jets[0].pT()/GeV;
101
102 size_t numTrans1(0), numTrans2(0), numAway(0);
103
104 // Calculate all the charged stuff
105 for (const Particle& p : cfs.particles()) {
106 const double dPhi = deltaPhi(p.phi(), jetphi);
107 const double pT = p.pT();
108 const double phi = p.phi();
109 double rotatedphi = phi - jetphi;
110 while (rotatedphi < 0) rotatedphi += 2*PI;
111
112 // @TODO: WARNING: The following lines are a hack to correct
113 // for the STAR tracking efficiency. Once we have the
114 // final numbers (corrected to hadron level), we need
115 // to remove this!!!!
116 if (1.0*rand()/static_cast<double>(RAND_MAX) > 0.87834-exp(-1.48994-0.788432*pT)) {
117 continue;
118 }
119 // -------- end of efficiency hack -------
120
121 if (dPhi < PI/3.0) {
122 // toward
123 }
124 else if (dPhi < 2*PI/3.0) {
125 if (rotatedphi <= PI) {
126 ++numTrans1;
127 }
128 else {
129 ++numTrans2;
130 }
131 }
132 else {
133 ++numAway;
134 }
135 } // end charged particle loop
136
137 // Fill the histograms
138 _hist_pmaxnchg->fill(jetpT, double(numTrans1>numTrans2 ? numTrans1 : numTrans2)/(2*PI/3));
139 _hist_pminnchg->fill(jetpT, double(numTrans1<numTrans2 ? numTrans1 : numTrans2)/(2*PI/3));
140 _hist_anchg->fill(jetpT, (double)numAway/(PI*0.7*0.7)); // jet area = pi*R^2
141
142 }
143
144
145 void finalize() {
146 /// @todo Really nothing to do?
147 }
148
149 /// @}
150
151
152 private:
153
154 Profile1DPtr _hist_pmaxnchg;
155 Profile1DPtr _hist_pminnchg;
156 Profile1DPtr _hist_anchg;
157
158 };
159
160
161 RIVET_DECLARE_PLUGIN(STAR_2009_UE_HELEN);
162
163}
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