// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief D_s -> eta, eta' semi-leptonic
class BESIII_2019_I1712742 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1712742);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS");
// histograms
for(unsigned int ix=0;ix<2;++ix)
for(unsigned int iy=0;iy<2;++iy)
book(_h[ix][iy],ix+1,1,iy+1);
// counter for normalization
book(_nDs, "TMP/nDs");
}
// Calculate the Q2 using mother and daugher meson
double q2(const Particle& B, int mesonID) {
FourMomentum q = B.mom() - filter_select(B.children(), Cuts::pid==mesonID)[0];
return q*q;
}
// Check for explicit decay into pdgids
bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
// Trivial check to ignore any other decays but the one in question modulo photons
const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
if (children.size()!=ids.size()) return false;
// Check for the explicit decay
return all(ids, [&](int i){return count(children, hasPID(i))==1;});
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Loop over Ds mesons
for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==431)) {
_nDs->fill();
if (isSemileptonicDecay(p, {PID::ETA, PID::POSITRON, PID::NU_E})) {
_h[0][0]->fill(q2(p, PID::ETA));
_h[0][1]->fill(q2(p, PID::ETA));
}
else if(isSemileptonicDecay(p, {PID::ETAPRIME, PID::POSITRON, PID::NU_E})) {
_h[1][0] ->fill(q2(p, PID::ETAPRIME));
_h[1][1] ->fill(q2(p, PID::ETAPRIME));
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
// D_s lifetime pdg2018 (ns)
double tau = 504e-6;
for(unsigned int ix=0;ix<2;++ix)
for(unsigned int iy=0;iy<2;++iy)
scale(_h[ix][iy],1./tau/ *_nDs);
}
/// @}
/// @name Histograms
/// @{
CounterPtr _nDs;
Histo1DPtr _h[2][2];
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2019_I1712742);
}