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## Rivet analyses reference

### CLEO_1990_I281039

$D_1(2420)^0$ and $D_2^*(2460)$ decay angle distributions
Experiment: CLEO (CESR)
Inspire ID: 281039
Status: VALIDATED
Authors:
• Peter Richardson
References:
• Phys.Rev. D41 (1990) 774
Beams: e- e+
Beam energies: (5.2, 5.2) GeV
No run details listed

Measurement of the $D_1(2420)^0$ and $D^*_2(2460)^0$ mesons at 10.5 GeV. The decay angle of the $D^{+*}$ with respect to the $D_1(2420)^0$ or $D^*_2(2460)^0$ direction in the rest frame of the parent hadron, is measured. This gives information on the spin of the parent.

Source code: CLEO_1990_I281039.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 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/FinalState.hh" #include "Rivet/Projections/UnstableParticles.hh" #include "Rivet/Projections/FastJets.hh" namespace Rivet { /// @brief D_1 D*2 decay angle class CLEO_1990_I281039 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(CLEO_1990_I281039); /// @name Analysis methods //@{ /// Book histograms and initialise projections before the run void init() { // Initialise and register projections declare(UnstableParticles(), "UFS"); // Book histograms book(_h_D1, 1, 1, 1); book(_h_D2, 1, 1, 2); } /// Recursively walk the decay tree to find decay products of @a p void findDecayProducts(Particle mother, Particles & dstar, Particles & pi,unsigned int & ncount) { for(const Particle & p: mother.children()) { if(p.abspid()==413) dstar.push_back(p); else if(p.abspid()==211) pi.push_back(p); ncount +=1; } } /// Perform the per-event analysis void analyze(const Event& event) { for(const Particle& p : apply(event, "UFS").particles(Cuts::abspid==425|| Cuts::abspid==10423)) { // decay products Particles dstar,pi; unsigned int ncount=0; findDecayProducts(p,dstar,pi,ncount); if(ncount!=2 || dstar.size()!=1 || pi.size()!=1) continue; if(dstar[0].pid()/p.pid()<0) continue; LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec()); Vector3 axis = boost.transform(dstar[0].momentum()).p3().unit(); double cosL = axis.dot(p.momentum().p3().unit()); // decay angles if(p.abspid()==425) _h_D2->fill(cosL); else _h_D1->fill(cosL); } } /// Normalise histograms etc., after the run void finalize() { normalize(_h_D1); normalize(_h_D2); } //@} /// @name Histograms //@{ Histo1DPtr _h_D1,_h_D2; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(CLEO_1990_I281039); }