Rivet analyses referenceLHCB_2012_I1208102Differential cross-sections of $\mathrm{Z}/\gamma^* \to e^{+}e^{-}$ vs rapidity and $\phi^*$Experiment: LHCb (LHC) Inspire ID: 1208102 Status: VALIDATED Authors:
Beam energies: (3500.0, 3500.0) GeV Run details:
Measurement of the $pp \to \mathrm{Z}^0$ cross-section in the $\mathrm{Z}/\gamma \to e^{+}e^{-}$ mode at $\sqrt{s} = 7$ TeV. Daughter electrons are required to have $p_T > 20$ GeV/$c$, $2 < \eta < 4.5$ and the dielectron invariant mass in range 60-120 GeV/$c^2$. The cross-section is given as a function of $Z$ rapidity and an angular variable ($\phi^*$) closely related to $Z$ transverse momentum (derived from the lepton pseudorapidity and azimuthal angle differences). For event generators implementing cross-section QCD corrections only at LO the distributions are normalized to the cross-section measured in data $76.0 \pm 0.8 \pm 2.0 \pm 2.6 \pm 0.4$ pb, where the first uncertainty is statistical, the second is systematic, the third is due to luminosity uncertainty and the fourth to FSR corrections. Source code: LHCB_2012_I1208102.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/ZFinder.hh"
4
5namespace Rivet {
6
7
8 /// Differential cross-sections of $\mathrm{Z}/\gamma^* \to e^{+}e^{-}$ vs rapidity and $\phi^*$
9 class LHCB_2012_I1208102 : public Analysis {
10 public:
11
12
13 /// Constructor
14 LHCB_2012_I1208102()
15 : Analysis("LHCB_2012_I1208102")
16 { }
17
18
19 /// @name Analysis methods
20 //@{
21
22 /// Book histograms
23 void init() {
24 ZFinder zeefinder(FinalState(), Cuts::etaIn(2.0, 4.5) && Cuts::pT > 20*GeV, PID::ELECTRON, 60*GeV, 120*GeV);
25 declare(zeefinder, "ZeeFinder");
26
27 book(_h_sigma_vs_y ,2, 1, 1);
28 book(_h_sigma_vs_phi ,3, 1, 1);
29 }
30
31
32 /// Do the analysis
33 void analyze(const Event& e) {
34 const ZFinder& zeefinder = apply<ZFinder>(e, "ZeeFinder");
35 if (zeefinder.empty()) vetoEvent;
36 if (zeefinder.bosons().size() > 1)
37 MSG_WARNING("Found multiple (" << zeefinder.bosons().size() << ") Z -> e+ e- decays!");
38
39 // Z momenta
40 const FourMomentum zee = zeefinder.bosons()[0].momentum();
41
42 if (zeefinder.constituents().size() < 2) vetoEvent;
43
44 const Particle pozitron = zeefinder.constituents()[0];
45 const Particle electron = zeefinder.constituents()[1];
46
47 // Calculation of the angular variable
48 const double diffphi = deltaPhi(pozitron, electron);
49 const double diffpsd = deltaEta(pozitron, electron);
50 const double accphi = M_PI - diffphi;
51 const double angular = tan(accphi/2) / cosh(diffpsd/2);
52
53 // Fill histograms
54 _h_sigma_vs_y->fill(zee.rapidity());
55 _h_sigma_vs_phi->fill(angular);
56 }
57
58
59 /// Finalize
60 void finalize() {
61 const double xs = crossSection()/picobarn;
62 scale(_h_sigma_vs_y, xs/sumOfWeights());
63 scale(_h_sigma_vs_phi, xs/sumOfWeights());
64 }
65
66 //@}
67
68
69 private:
70
71 /// @name Histograms
72 //@{
73 Histo1DPtr _h_sigma_vs_y, _h_sigma_vs_phi;
74 //@}
75
76 };
77
78
79 // The hook for the plugin system
80 RIVET_DECLARE_PLUGIN(LHCB_2012_I1208102);
81
82}
|