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Rivet analyses reference
BESIII_2015_I1373915
Radiative $J/\psi$ decays to $\pi^0\pi^0$
Experiment: BESIII (BEPC)
Inspire ID: 1373915
Status: VALIDATED NOHEPDATA
Authors:
References:
- Phys.Rev.D 92 (2015) 5, 052003
Beams: * *
Beam energies: ANY
Run details:
- Any process producing J/psi, originally e+e-
Measurement of the $\pi^0\pi^0$ mass distribution in the decay $J/\psi\to\gamma\pi^0\pi^0$. Plots were read from the paper and are not corrected for efficiency/acceptance, although the backgrounds given in the paper were subtracted.
Source code:
BESIII_2015_I1373915.cc
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64 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief J/psi -> gamma pi0 pi0
class BESIII_2015_I1373915 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2015_I1373915);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
UnstableParticles ufs = UnstableParticles(Cuts::abspid==443);
declare(ufs, "UFS");
DecayedParticles PSI(ufs);
PSI.addStable(PID::PI0);
declare(PSI, "PSI");
book(_h,1,1,1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// find the J/psi decays
static const map<PdgId,unsigned int> & mode = { { 111,2},{ 22,1}};
DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
if( PSI.decaying().size()!=1) vetoEvent;
if(!PSI.modeMatches(0,3,mode)) vetoEvent;
// particles
const Particles & pi0 = PSI.decayProducts()[0].at(111);
double mpipi = (pi0[0].momentum()+pi0[1].momentum()).mass();
_h->fill(mpipi);
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h,1.,false);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h;
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2015_I1373915);
}
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