Rivet analyses referenceD0_2010_S8821313Precise study of Z pT using novel 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_S8821313.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Tools/BinnedHistogram.hh"
4#include "Rivet/Projections/FinalState.hh"
5#include "Rivet/Projections/ZFinder.hh"
6
7namespace Rivet {
8
9
10 class D0_2010_S8821313 : public Analysis {
11 public:
12
13 RIVET_DEFAULT_ANALYSIS_CTOR(D0_2010_S8821313);
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 = (Cuts::abseta < 1.1 || Cuts::absetaIn( 1.5, 3.0)) && Cuts::pT > 20*GeV;
25 ZFinder zfinder_ee(fs, cuts, PID::ELECTRON, 70*GeV, 110*GeV, 0.2, ZFinder::ClusterPhotons::NODECAY, ZFinder::AddPhotons::YES);
26 declare(zfinder_ee, "zfinder_ee");
27 ZFinder zfinder_mm(fs, Cuts::abseta < 2 && Cuts::pT > 15*GeV, PID::MUON, 70*GeV, 110*GeV, 0.0, ZFinder::ClusterPhotons::NONE, ZFinder::AddPhotons::NO);
28 declare(zfinder_mm, "zfinder_mm");
29
30 /// Book histograms here
31 {Histo1DPtr tmp; _h_phistar_ee.add(0.0, 1.0, book(tmp, 1, 1, 1));}
32 {Histo1DPtr tmp; _h_phistar_ee.add(1.0, 2.0, book(tmp, 1, 1, 2));}
33 {Histo1DPtr tmp; _h_phistar_ee.add(2.0, 10.0,book(tmp, 1, 1, 3));}
34 {Histo1DPtr tmp; _h_phistar_mm.add(0.0, 1.0, book(tmp, 2, 1, 1));}
35 {Histo1DPtr tmp; _h_phistar_mm.add(1.0, 2.0, book(tmp, 2, 1, 2));}
36 }
37
38
39 /// Perform the per-event analysis
40 void analyze(const Event& event) {
41 const double weight = 1.0;
42
43 const ZFinder& zfinder_ee = apply<ZFinder>(event, "zfinder_ee");
44 if (zfinder_ee.bosons().size() == 1) {
45 Particles ee = zfinder_ee.constituents();
46 std::sort(ee.begin(), ee.end(), cmpMomByPt);
47 const FourMomentum& eminus = PID::charge3(ee[0].pid()) < 0 ? ee[0].momentum() : ee[1].momentum();
48 const FourMomentum& eplus = PID::charge3(ee[0].pid()) < 0 ? ee[1].momentum() : ee[0].momentum();
49 double phi_acop = M_PI - mapAngle0ToPi(eminus.phi() - eplus.phi());
50 double costhetastar = tanh((eminus.eta() - eplus.eta())/2);
51 double sin2thetastar = 1 - sqr(costhetastar);
52 if (sin2thetastar < 0) sin2thetastar = 0;
53 const double phistar = tan(phi_acop/2) * sqrt(sin2thetastar);
54 const FourMomentum& zmom = zfinder_ee.bosons()[0].momentum();
55 _h_phistar_ee.fill(zmom.rapidity(), phistar, weight);
56 }
57
58 const ZFinder& zfinder_mm = apply<ZFinder>(event, "zfinder_mm");
59 if (zfinder_mm.bosons().size() == 1) {
60 Particles mm = zfinder_mm.constituents();
61 std::sort(mm.begin(), mm.end(), cmpMomByPt);
62 const FourMomentum& mminus = PID::charge3(mm[0].pid()) < 0 ? mm[0].momentum() : mm[1].momentum();
63 const FourMomentum& mplus = PID::charge3(mm[0].pid()) < 0 ? mm[1].momentum() : mm[0].momentum();
64 double phi_acop = M_PI - mapAngle0ToPi(mminus.phi() - mplus.phi());
65 double costhetastar = tanh((mminus.eta() - mplus.eta())/2);
66 double sin2thetastar = 1 - sqr(costhetastar);
67 if (sin2thetastar < 0) sin2thetastar = 0;
68 const double phistar = tan(phi_acop/2) * sqrt(sin2thetastar);
69 const FourMomentum& zmom = zfinder_mm.bosons()[0].momentum();
70 _h_phistar_mm.fill(zmom.rapidity(), phistar, weight);
71 }
72 }
73
74
75 /// Normalise histograms etc., after the run
76 void finalize() {
77 for (Histo1DPtr hist : _h_phistar_ee.histos()) normalize(hist);
78 for (Histo1DPtr hist : _h_phistar_mm.histos()) normalize(hist);
79 }
80
81 //@}
82
83
84 private:
85
86 /// @name Histograms
87 //@{
88 BinnedHistogram _h_phistar_ee;
89 BinnedHistogram _h_phistar_mm;
90 //@}
91
92
93 };
94
95
96
97 RIVET_DECLARE_ALIASED_PLUGIN(D0_2010_S8821313, D0_2010_I871787);
98
99}
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