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## Rivet analyses reference

### LHCB_2012_I1208102

Differential cross-sections of $\mathrm{Z}/\gamma^* \to e^{+}e^{-}$ vs rapidity and $\phi^*$
Experiment: LHCb (LHC)
Inspire ID: 1208102
Status: VALIDATED
Authors:
• Ana Elena Dumitriu
• Marek Sirendi
• David Ward
• Alex Grecu
References:
Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
• $\mathrm{Z}/\gamma^* \to e^{+}e^{-}_$ decays with di-lepton invariant mass $> 40$ GeV/$c^2$ produced in $pp$ collisions at $\sqrt{s}=7$ TeV.

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 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 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/ZFinder.hh" namespace Rivet { /// Differential cross-sections of $\mathrm{Z}/\gamma^* \to e^{+}e^{-}$ vs rapidity and $\phi^*$ class LHCB_2012_I1208102 : public Analysis { public: /// Constructor LHCB_2012_I1208102() : Analysis("LHCB_2012_I1208102") { } /// @name Analysis methods //@{ /// Book histograms void init() { ZFinder zeefinder(FinalState(), Cuts::etaIn(2.0, 4.5) && Cuts::pT > 20*GeV, PID::ELECTRON, 60*GeV, 120*GeV); declare(zeefinder, "ZeeFinder"); _h_sigma_vs_y = bookHisto1D(2, 1, 1); _h_sigma_vs_phi = bookHisto1D(3, 1, 1); } /// Do the analysis void analyze(const Event& e) { const ZFinder& zeefinder = apply(e, "ZeeFinder"); if (zeefinder.empty()) vetoEvent; if (zeefinder.bosons().size() > 1) MSG_WARNING("Found multiple (" << zeefinder.bosons().size() << ") Z -> e+ e- decays!"); // Z momenta const FourMomentum zee = zeefinder.bosons()[0].momentum(); const Particle pozitron = zeefinder.constituents()[0]; const Particle electron = zeefinder.constituents()[1]; // Calculation of the angular variable const double diffphi = deltaPhi(pozitron, electron); const double diffpsd = deltaEta(pozitron, electron); const double accphi = M_PI - diffphi; const double angular = tan(accphi/2) / cosh(diffpsd/2); // Fill histograms _h_sigma_vs_y->fill(zee.rapidity(), e.weight()); _h_sigma_vs_phi->fill(angular, e.weight()); } /// Finalize void finalize() { const double xs = crossSection()/picobarn; scale(_h_sigma_vs_y, xs/sumOfWeights()); scale(_h_sigma_vs_phi, xs/sumOfWeights()); } //@} private: /// @name Histograms //@{ Histo1DPtr _h_sigma_vs_y, _h_sigma_vs_phi; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(LHCB_2012_I1208102); }