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## Rivet analyses reference

### ARGUS_1989_I268577

Spectrum and decay angle for $D^0_{2}$ production in $e^+e^-$ at 10 GeV in the continuum
Experiment: ARGUS (DORIS)
Inspire ID: 268577
Status: VALIDATED
Authors:
• Peter Richardson
References:
• Phys.Lett. B221 (1989) 422-426
Beams: e- e+
Beam energies: (5.0, 5.0) GeV
Run details:
• $e^+ e^-$ analysis near the $\Upsilon$ resonances

Measurement of the $D^*_2(2460)^0$ spectrum in $e^+e^-$ collisions at 10 GeV. The decay angle of the $D^{+*}$ with respect to the $D^*_2(2460)^0$ direction in the rest frame of the parent hadron, this gives information on the spin of the parent, is also measured.

Source code: ARGUS_1989_I268577.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 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/UnstableParticles.hh" namespace Rivet { /// @brief D*2 spectrum and decay angle class ARGUS_1989_I268577 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(ARGUS_1989_I268577); /// @name Analysis methods //@{ /// Book histograms and initialise projections before the run void init() { // Initialise and register projections declare(UnstableParticles(), "UFS"); // Book histograms book(_h_D2_x , 2, 1, 1); book(_h_D2_ctheta, 3, 1, 1); } /// 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) { const UnstableParticles& ufs = apply(event, "UFS"); for (const Particle& p : ufs.particles(Cuts::abspid==425)) { const double xp = 2.*p.p3().mod()/sqrtS(); _h_D2_x->fill(xp); // 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 _h_D2_ctheta->fill(cosL); } } /// Normalise histograms etc., after the run void finalize() { normalize(_h_D2_x); normalize(_h_D2_ctheta); } //@} /// @name Histograms //@{ Histo1DPtr _h_D2_x,_h_D2_ctheta; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(ARGUS_1989_I268577); }