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## Rivet analyses reference

### ARGUS_1989_I280943

Spectra and decay distributions for $D_1(2420)^0$ and $D^*_2(2460)^0$ production in $e^+e^-$ collisions at 10 GeV
Experiment: ARGUS (DORIS)
Inspire ID: 280943
Status: VALIDATED
Authors:
• Peter Richardson
References:
• Phys.Lett. B232 (1989) 398-404
Beams: e- e+
Beam energies: ANY
Run details:
Measurements of the scaled momentum spectrum for $D_1(2420)^0$ and $D^*_2(2460)^0$ production in $e^+e^-$ collisions at 10 GeV. The decays $D_1(2420)^0, D^*_2(2460)^0 \to D^{*+}\pi^-\to D^0\pi^+\pi^-$ were used and the helicity angle, i.e. the angle between the two pions in the rest frame of the $D^*$ are is measured.
  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 99 100 101 102 103 104 105 106 107 108 109 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/UnstableParticles.hh" namespace Rivet { /// @brief D_1 and D_2 spectra and decay distributions class ARGUS_1989_I280943 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(ARGUS_1989_I280943); /// @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_x ,4,1,1); book(_h_D2_x ,4,1,2); book(_h_D1_alpha,3,1,1); book(_h_D2_alpha,3,1,2); } /// Recursively walk the decay tree to find decay products of @a p void findDecayProducts(Particle mother, Particles & dstar, Particles & d0, Particles & pi,unsigned int & ncount) { for(const Particle & p: mother.children()) { if(p.abspid()==413) dstar.push_back(p); else if(p.abspid()==421) d0.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)) { const double xp = 2.*p.p3().mod()/sqrtS(); // spectra if(p.abspid()==425) _h_D2_x->fill(xp); else _h_D1_x->fill(xp); // decay products Particles dstar,d0,pi; unsigned int ncount=0; findDecayProducts(p,dstar,d0, pi,ncount); if(ncount!=2 || dstar.size()!=1 || pi.size()!=1 || d0.size()!=0 ) continue; if(dstar[0].pid()/p.pid()<0) continue; Particle p2 = dstar[0]; LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p2.momentum().betaVec()); Vector3 d1 = boost.transform(pi[0].momentum()).p3().unit(); ncount=0; dstar.clear(); d0.clear(); pi.clear(); findDecayProducts(p2,dstar,d0, pi,ncount); if(ncount!=2 || dstar.size()!=0 || pi.size()!=1 || d0.size()!=1 ) continue; if(pi[0].pid()/p2.pid()<0) continue; Vector3 d2 = boost.transform(pi[0].momentum()).p3().unit(); double cosAlpha = abs(d1.dot(d2)); // decay angles if(p.abspid()==425) _h_D2_alpha->fill(cosAlpha); else _h_D1_alpha->fill(cosAlpha); } } /// Normalise histograms etc., after the run void finalize() { normalize(_h_D1_x); normalize(_h_D2_x); normalize(_h_D1_alpha); normalize(_h_D2_alpha); } //@} /// @name Histograms //@{ Histo1DPtr _h_D1_x, _h_D2_x; Histo1DPtr _h_D1_alpha, _h_D2_alpha; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(ARGUS_1989_I280943); }