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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief q^2 in B0 -> pi- l+ nu_l decays
class BELLE_2011_I878990 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2011_I878990);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS");
// Book histograms
book(_h_q2 ,1, 1, 1);
}
// 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 B0 mesons
for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==PID::B0)) {
if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E}) ||
isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU})) {
_h_q2->fill(q2(p, PID::PIMINUS));
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_q2, 3000.86); // normalize to BF*dQ2
}
//@}
private:
/// @name Histograms
//@{
Histo1DPtr _h_q2;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(BELLE_2011_I878990);
}
|