Rivet analyses referenceD0_2010_I871787Precise study of Z pT using novel phi* techniqueExperiment: D0 (Tevatron Run 2) Inspire ID: 871787 Status: VALIDATED Authors:
Beam energies: (980.0, 980.0) GeV Run details:
Using 7.3 pb$^{-1}$ the distribution of the variable $\phi^*$ is measured, which probes the same physical effects as the $Z/\gamma^*$ boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. Results are presented for both the di-electron and di-muon channel. Source code: D0_2010_I871787.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/DileptonFinder.hh"
5
6namespace Rivet {
7
8
9 /// Precise study of Z pT using novel phi* technique
10 class D0_2010_I871787 : public Analysis {
11 public:
12
13 RIVET_DEFAULT_ANALYSIS_CTOR(D0_2010_I871787);
14
15
16 /// @name Analysis methods
17 /// @{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21
22 /// Initialise and register projections
23 FinalState fs;
24 Cut cuts_e = (Cuts::abseta < 1.1 || Cuts::absetaIn( 1.5, 3.0)) && Cuts::pT > 20*GeV;
25 DileptonFinder zfinder_ee(91.2*GeV, 0.2, cuts_e && Cuts::abspid == PID::ELECTRON, Cuts::massIn(70*GeV, 110*GeV));
26 declare(zfinder_ee, "zfinder_ee");
27 Cut cuts_m = Cuts::abseta < 2 && Cuts::pT > 15*GeV;
28 DileptonFinder zfinder_mm(91.2*GeV, 0.0, cuts_m && Cuts::abspid == PID::MUON, Cuts::massIn(70*GeV, 110*GeV));
29 declare(zfinder_mm, "zfinder_mm");
30
31 /// Book histograms here
32 book(_h_phistar_ee, {0., 1., 2., 10.}, {"d01-x01-y01", "d01-x01-y02", "d01-x01-y03"});
33 book(_h_phistar_mm, {0., 1., 2.}, {"d02-x01-y01", "d02-x01-y02"});
34 }
35
36
37 /// Perform the per-event analysis
38 void analyze(const Event& event) {
39
40 const DileptonFinder& zfinder_ee = apply<DileptonFinder>(event, "zfinder_ee");
41 if (zfinder_ee.bosons().size() == 1) {
42 Particles ee = zfinder_ee.constituents();
43 std::sort(ee.begin(), ee.end(), cmpMomByPt);
44 const FourMomentum& eminus = PID::charge3(ee[0].pid()) < 0 ? ee[0].momentum() : ee[1].momentum();
45 const FourMomentum& eplus = PID::charge3(ee[0].pid()) < 0 ? ee[1].momentum() : ee[0].momentum();
46 double phi_acop = M_PI - mapAngle0ToPi(eminus.phi() - eplus.phi());
47 double costhetastar = tanh((eminus.eta() - eplus.eta())/2);
48 double sin2thetastar = 1 - sqr(costhetastar);
49 if (sin2thetastar < 0) sin2thetastar = 0;
50 const double phistar = tan(phi_acop/2) * sqrt(sin2thetastar);
51 const FourMomentum& zmom = zfinder_ee.bosons()[0].momentum();
52 _h_phistar_ee->fill(zmom.rapidity(), phistar);
53 }
54
55 const DileptonFinder& zfinder_mm = apply<DileptonFinder>(event, "zfinder_mm");
56 if (zfinder_mm.bosons().size() == 1) {
57 Particles mm = zfinder_mm.constituents();
58 std::sort(mm.begin(), mm.end(), cmpMomByPt);
59 const FourMomentum& mminus = PID::charge3(mm[0].pid()) < 0 ? mm[0].momentum() : mm[1].momentum();
60 const FourMomentum& mplus = PID::charge3(mm[0].pid()) < 0 ? mm[1].momentum() : mm[0].momentum();
61 double phi_acop = M_PI - mapAngle0ToPi(mminus.phi() - mplus.phi());
62 double costhetastar = tanh((mminus.eta() - mplus.eta())/2);
63 double sin2thetastar = 1 - sqr(costhetastar);
64 if (sin2thetastar < 0) sin2thetastar = 0;
65 const double phistar = tan(phi_acop/2) * sqrt(sin2thetastar);
66 const FourMomentum& zmom = zfinder_mm.bosons()[0].momentum();
67 _h_phistar_mm->fill(zmom.rapidity(), phistar);
68 }
69 }
70
71
72 /// Normalise histograms etc., after the run
73 void finalize() {
74 normalize({_h_phistar_ee, _h_phistar_mm});
75 }
76
77 /// @}
78
79
80 private:
81
82 /// @name Histograms
83 /// @{
84 Histo1DGroupPtr _h_phistar_ee, _h_phistar_mm;
85 /// @}
86
87
88 };
89
90
91
92 RIVET_DECLARE_ALIASED_PLUGIN(D0_2010_I871787, D0_2010_S8821313);
93
94}
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