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## Rivet analyses reference

### BELLE_2001_S4598261

Measurement of inclusive production of neutral pions from $\Upsilon(4S)$ decays.
Experiment: Belle (KEKB)
Inspire ID: 554520
Status: VALIDATED
Authors:
• Peter Richardson
References:
• Phys.Rev. D64 (2001) 072001
• hep-ex/0103041
Beams: e+ e-
Beam energies: (3.5, 8.0) GeV
Run details:
• $e^+ e^-$ analysis on the $\Upsilon(4S)$ resonance, with CoM boosts of 8.0 GeV ($e^-$) and 3.5 GeV ($e^+$)

Measurement of the mean multiplicity and the momentum spectrum of neutral pions from the decays of the Upsilon(4S) resonance using the Belle detector operating at the KEKB $e^+e^-$ storage ring. Useful for tuning $B$ meson decay models.

Source code: BELLE_2001_S4598261.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 95 96 97 98 99 100 101 102 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/Beam.hh" #include "Rivet/Projections/UnstableParticles.hh" namespace Rivet { /// @brief BELLE pi0 spectrum at Upsilon(4S) /// @author Peter Richardson class BELLE_2001_S4598261 : public Analysis { public: BELLE_2001_S4598261() : Analysis("BELLE_2001_S4598261") { } void init() { declare(UnstableParticles(), "UFS"); book(_histdSigDp ,1, 1, 1); // spectrum book(_histMult ,2, 1, 1); // multiplicity book(_weightSum, "TMP/weightSum"); } void analyze(const Event& e) { // Find the upsilons Particles upsilons; // First in unstable final state const UnstableParticles& ufs = apply(e, "UFS"); for (const Particle& p : ufs.particles()) if (p.pid()==300553) upsilons.push_back(p); // Then in whole event if fails if (upsilons.empty()) { for(ConstGenParticlePtr p: HepMCUtils::particles(e.genEvent())) { if (p->pdg_id() != 300553) continue; ConstGenVertexPtr pv = p->production_vertex(); bool passed = true; if (pv) { for (ConstGenParticlePtr pp: HepMCUtils::particles(pv, Relatives::PARENTS)){ if ( p->pdg_id() == pp->pdg_id() ) { passed = false; break; } } } if (passed) upsilons.push_back(Particle(p)); } } // Find upsilons for (const Particle& p : upsilons) { _weightSum->fill(); // Find the neutral pions from the decay vector pions; findDecayProducts(p.genParticle(), pions); const LorentzTransform cms_boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec()); for (size_t ix=0; ixmomentum())).p(); _histdSigDp->fill(pcm); } _histMult->fill(0., pions.size()); } } void finalize() { scale(_histdSigDp, 1./ *_weightSum); scale(_histMult , 1./ *_weightSum); } private: //@{ // count of weights CounterPtr _weightSum; /// Histograms Histo1DPtr _histdSigDp; Histo1DPtr _histMult; //@} void findDecayProducts(ConstGenParticlePtr p, vector& pions) { ConstGenVertexPtr dv = p->end_vertex(); for (ConstGenParticlePtr pp: HepMCUtils::particles(dv, Relatives::CHILDREN)){ const int id = pp->pdg_id(); if (id == 111) { pions.push_back(pp); } else if (pp->end_vertex()) findDecayProducts(pp, pions); } } }; DECLARE_RIVET_PLUGIN(BELLE_2001_S4598261); }