rivet is hosted by Hepforge, IPPP Durham

## Rivet analyses reference

### MARKII_1979_I144382

$\pi^+\pi^-$ spectrum in $\psi(2S)\to\pi^+\pi^-J/\psi$
Experiment: MARKII (SPEAR)
Inspire ID: 144382
Status: VALIDATED
Authors:
• Peter Richardson
No references listed
Beams: * *
Beam energies: ANY
No run details listed

Measurement of the mass spectrum for $\pi^+\pi^-$ in $\psi(2S)\to\pi^+\pi^-J/\psi$ decays by the MARK-II experiment.

Source code: MARKII_1979_I144382.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 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/UnstableParticles.hh" namespace Rivet { /// @brief psi(2S) -> J/psi pi+pi- class MARKII_1979_I144382 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(MARKII_1979_I144382); /// @name Analysis methods ///@{ /// Book histograms and initialise projections before the run void init() { // Initialise and register projections declare(UnstableParticles(),"UFS"); book(_hist, 1, 1, 1); } void findDecayProducts(const Particle & mother, unsigned int & nstable, Particles& pip, Particles& pim, Particles & onium) { for(const Particle & p : mother.children()) { int id = p.pid(); if ( id == PID::PIMINUS) { pim.push_back(p); ++nstable; } else if (id == PID::PIPLUS) { pip.push_back(p); ++nstable; } else if (id==443) { onium.push_back(p); ++nstable; } else if ( !p.children().empty() ) { findDecayProducts(p,nstable,pip,pim,onium); } else ++nstable; } } /// Perform the per-event analysis void analyze(const Event& event) { // loop over unstable particles for(const Particle& ups : apply(event, "UFS").particles(Cuts::pid==100443)) { unsigned int nstable(0); Particles pip, pim, onium; findDecayProducts(ups,nstable,pip,pim,onium); // check for onium if(onium.size() !=1 || nstable !=3 || pip.size()!=1 || pim.size() !=1 ) continue; FourMomentum q = pip[0].momentum()+pim[0].momentum(); _hist->fill(q.mass2()); } } /// Normalise histograms etc., after the run void finalize() { normalize(_hist); } ///@} /// @name Histograms ///@{ Histo1DPtr _hist; ///@} }; DECLARE_RIVET_PLUGIN(MARKII_1979_I144382); }