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## Rivet analyses reference

### ATLAS_2014_I1282441

The differential production cross section of the $\phi(1020)$ meson in $\sqrt{s}=7$ TeV $pp$ collisions measured with the ATLAS detector
Experiment: ATLAS (LHC)
Inspire ID: 1282441
Status: VALIDATED
Authors:
• Tim Martin
• Kiran Joshi
References:
Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
• Run minimum bias events

A measurement is presented of the $\phi \rightarrow K^+K^-$ production cross section at $\sqrt{s}$ = 7 TeV using pp collision data corresponding to an integrated luminosity of 383 $\mu$b$^{-1}$ collected with the ATLAS experiment at the LHC. Selection of $\phi(1020)$ mesons is based on the identification of charged kaons by their energy loss in the pixel detector. The differential cross section is measured as a function of the transverse momentum, $pT,\phi$, and rapidity, $y_\phi$, of the $\phi(1020)$ meson in the fiducial region 500 < $pT,\phi$ < 1200 MeV, |$y_\phi$| < 0.8, kaon $pT,K$ > 230 MeV and kaon momentum $p_K$ < 800 MeV. The integrated $\phi(1020)$ production cross section in this fiducial range is measured to be $\sigma_{\phi \rightarrow K^+K^-}$ = 570 \pm 8 (stat) \pm 66 (syst) \pm 20 (lumi) $\mu$b.

Source code: ATLAS_2014_I1282441.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 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/FinalState.hh" #include "Rivet/Projections/UnstableFinalState.hh" #include "Rivet/Projections/IdentifiedFinalState.hh" namespace Rivet { class ATLAS_2014_I1282441 : public Analysis { public: ATLAS_2014_I1282441() : Analysis("ATLAS_2014_I1282441") { } void init() { // Use a large eta range such that we can discriminate on y /// @todo Convert to use a y-cut directly UnstableFinalState ufs(Cuts::abseta < 10 && Cuts::pT > 500*MeV); IdentifiedFinalState phis(ufs); phis.acceptIdPair(PID::PHI); declare(phis, "Phis"); IdentifiedFinalState kpms(Cuts::abseta < 2.0 && Cuts::pT > 230*MeV); kpms.acceptIdPair(PID::KPLUS); declare(kpms, "Kpms"); _h_phi_rapidity = bookHisto1D(1,1,1); _h_phi_pT = bookHisto1D(2,1,1); } void analyze(const Event& event) { const Particles& ks_all = apply(event, "Kpms").particles(); Particles kp, km; foreach (const Particle& p, ks_all) { if (!p.hasAncestor(PID::PHI)) { MSG_DEBUG("-- K not from phi."); continue; } if (p.p3().mod() > 800*MeV) { MSG_DEBUG("-- p K too high."); continue; } (p.charge() > 0 ? kp : km).push_back(p); } const Particles& phis_all = apply(event, "Phis").particles(); Particles phis; /// @todo Use particles(Cuts&) instead foreach (const Particle& p, phis_all) { if ( p.absrap() > 0.8 ) { MSG_DEBUG("-- phi Y too high."); continue; } if ( p.pT() > 1.2*GeV ) { MSG_DEBUG("-- phi pT too high."); continue; } phis.push_back(p); } // Find Phi -> KK decays through matching of the kinematics if (!kp.empty() && !km.empty() && !phis.empty()) { const double w = event.weight(); MSG_DEBUG("Numbers of particles: #phi=" << phis.size() << ", #K+=" << kp.size() << ", #K-=" << km.size()); for (size_t ip = 0; ip < phis.size(); ++ip) { const Particle& phi = phis[ip]; for (size_t ikm = 0; ikm < km.size(); ++ikm) { for (size_t ikp = 0; ikp < kp.size(); ++ikp) { const FourMomentum mom = kp[ikp].mom() + km[ikm].mom(); if ( fuzzyEquals(mom.mass(), phi.mass(), 1e-5) ) { MSG_DEBUG("Accepted combinatoric: phi#:" << ip << " K+#:" << ikp << " K-#:" << ikm); _h_phi_rapidity->fill(phi.absrap(), w); _h_phi_pT->fill(phi.pT()/MeV, w); } else { MSG_DEBUG("Rejected combinatoric: phi#:" << ip << " K+#:" << ikp << " K-#:" << ikm << " Mass difference is " << mom.mass()-phi.mass()); } } } } } } void finalize() { scale(_h_phi_rapidity, crossSection()/microbarn/sumOfWeights()); scale(_h_phi_pT, crossSection()/microbarn/sumOfWeights()); } private: Histo1DPtr _h_phi_rapidity, _h_phi_pT; }; DECLARE_RIVET_PLUGIN(ATLAS_2014_I1282441); }