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ARGUS_1990_I278933

$\pi^0$ and $\eta$ spectra for $e^+e^-$ collisions in the continuum at 9.46 GeV and at $\Upsilon_{1,2}$
Experiment: ARGUS (DORIS)
Inspire ID: 278933
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Z.Phys. C46 (1990) 15, 1990
Beams: e- e+
Beam energies: (4.7, 4.7); (5.0, 5.0) GeV
Run details:
  • $e^+ e^-$ analysis near the $\Upsilon$ resonances

Measurement of the inclusive production of the $\pi^0$ and $\eta$ mesons in $e^+e^-$ annihilation in the Upsilon region. Data are taken on the $\Upsilon(1S)$, $\Upsilon(2S)$ and in the nearby continuum.

Source code: ARGUS_1990_I278933.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4
  5namespace Rivet {
  6
  7
  8  /// @brief pi0 and eta at Upsilon 1,2 and continuum
  9  class ARGUS_1990_I278933 : public Analysis {
 10  public:
 11
 12    /// Constructor
 13    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1990_I278933);
 14
 15
 16    /// @name Analysis methods
 17    /// @{
 18
 19    /// Book histograms and initialise projections before the run
 20    void init() {
 21      // Initialise and register projections
 22      declare(UnstableParticles(), "UFS");
 23      // Book histograms
 24      book(_n_Pi[0] ,   1, 1, 1);
 25      book(_n_Pi[1] ,   1, 1, 2);
 26      book(_n_Pi[2] ,   1, 1, 3);
 27      book(_n_Eta[0],   2, 1, 1);
 28      book(_n_Eta[1],   2, 1, 2);
 29      book(_n_Eta[2],   2, 1, 3);
 30      book(_h_cont_pi1 ,3, 1, 1);
 31      book(_h_cont_pi2 ,3, 1, 2);
 32      book(_h_ups1_pi  ,4, 1, 1);
 33      book(_h_ups2_pi  ,4, 1, 2);
 34      book(_h_cont_eta1,5, 1, 1);
 35      book(_h_cont_eta2,5, 1, 2);
 36      book(_h_ups1_eta ,6, 1, 1);
 37      book(_h_ups2_eta ,6, 1, 2);
 38      book(_weightSum_cont,"/TMP/weightSum_cont");
 39      book(_weightSum_Ups1,"/TMP/weightSum_Ups1");
 40      book(_weightSum_Ups2,"/TMP/weightSum_Ups2");
 41
 42    }
 43
 44    /// Recursively walk the decay tree to find decay products of @a p
 45    void findDecayProducts(Particle mother, Particles& unstable) {
 46      for (const Particle & p: mother.children()) {
 47        const int id = p.pid();
 48        if(id == 111 or id == 221) {
 49          unstable.push_back(p);
 50        }
 51        if(!p.children().empty()) {
 52          findDecayProducts(p, unstable);
 53        }
 54      }
 55    }
 56
 57    /// Perform the per-event analysis
 58    void analyze(const Event& event) {
 59      // Find the Upsilons among the unstables
 60      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
 61      Particles upsilons = ufs.particles(Cuts::pid==553 or Cuts::pid==100553);
 62      // Continuum
 63      if (upsilons.empty()) {
 64        MSG_DEBUG("No Upsilons found => continuum event");
 65        _weightSum_cont->fill();
 66        for (const Particle& p : ufs.particles(Cuts::pid==111 or Cuts::pid==221)) {
 67          const int id = p.pid();
 68          const double xp = 2.*p.E()/sqrtS();
 69          const double beta = p.p3().mod() / p.E();
 70          if(id==111) {
 71            _n_Pi[0]->fill(10);
 72            _h_cont_pi1->fill(xp,1./beta);
 73            _h_cont_pi2->fill(xp,1./beta);
 74          }
 75          else {
 76            _n_Eta[0]->fill(10);
 77            _h_cont_eta1->fill(xp,1./beta);
 78            _h_cont_eta2->fill(xp,1./beta);
 79          }
 80        }
 81      }
 82      // Upsilon(s) found
 83      else {
 84        MSG_DEBUG("Upsilons found => resonance event");
 85        for (const Particle& ups : upsilons) {
 86          const int parentId = ups.pid();
 87          if(parentId==553) {
 88            _weightSum_Ups1->fill();
 89          }
 90          else {
 91            _weightSum_Ups2->fill();
 92          }
 93          Particles unstable;
 94          // Find the decay products we want
 95          findDecayProducts(ups, unstable);
 96          LorentzTransform cms_boost;
 97          if (ups.p3().mod() > 1*MeV)
 98            cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
 99          const double mass = ups.mass();
100          // loop over decay products
101          for(const Particle& p : unstable) {
102            const int id = p.pid();
103            const FourMomentum p2 = cms_boost.transform(p.momentum());
104            const double xp = 2.*p2.E()/mass;
105            const double beta = p2.p3().mod()/p2.E();
106            if (id==111) {
107              if (parentId==553) {
108                _n_Pi[1]->fill(10);
109                _h_ups1_pi->fill(xp,1./beta);
110              }
111              else {
112                _n_Pi[2]->fill(10);
113                _h_ups2_pi->fill(xp,1./beta);
114              }
115            }
116            else if(id==221) {
117              if (parentId==553) {
118                _n_Eta[1]->fill(10);
119                _h_ups1_eta->fill(xp,1./beta);
120              }
121              else {
122                _n_Eta[2]->fill(10);
123                _h_ups2_eta->fill(xp,1./beta);
124              }
125            }
126          }
127        }
128      }
129    }
130
131
132    /// Normalise histograms etc., after the run
133    void finalize() {
134
135      // Scale histos
136      if (_weightSum_cont->val() > 0.) {
137        scale(_h_cont_pi1, 1./ *_weightSum_cont);
138        scale(_h_cont_pi2, sqr(sqrtS())*crossSection()/microbarn/sumOfWeights());
139        scale(_h_cont_eta1, 1./ *_weightSum_cont);
140        scale(_h_cont_eta2, sqr(sqrtS())*crossSection()/microbarn/sumOfWeights());
141      }
142      if (_weightSum_Ups1->val() > 0.) {
143        scale(_h_ups1_pi, 1./ *_weightSum_Ups1);
144        scale(_h_ups1_eta, 1./ *_weightSum_Ups1);
145      }
146      if (_weightSum_Ups2->val() > 0.) {
147        scale(_h_ups2_pi, 1./ *_weightSum_Ups2);
148        scale(_h_ups2_eta, 1./ *_weightSum_Ups2);
149      }
150      // Counters
151      vector<CounterPtr> scales = {_weightSum_cont,_weightSum_Ups1,_weightSum_Ups2};
152      for (unsigned int ix=0; ix<3; ++ix) {
153        scale(_n_Pi[ix],  1./ *scales[ix]);
154        scale(_n_Eta[ix], 1./ *scales[ix]);
155      }
156    }
157
158    /// @}
159
160
161    /// @name Histograms
162    /// @{
163    Histo1DPtr _h_cont_pi1 , _h_cont_pi2 , _h_ups1_pi , _h_ups2_pi ;
164    Histo1DPtr _h_cont_eta1, _h_cont_eta2, _h_ups1_eta, _h_ups2_eta;
165    BinnedHistoPtr<int> _n_Eta[3],_n_Pi[3];
166    CounterPtr _weightSum_cont,_weightSum_Ups1,_weightSum_Ups2;
167    /// @}
168
169
170  };
171
172
173  RIVET_DECLARE_PLUGIN(ARGUS_1990_I278933);
174
175
176}