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105 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief B -> X_s gamma spectrum
class BABAR_2008_I769107 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I769107);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS");
// Book histograms
book(_h_spectrum, 1, 1, 1);
book(_nBottom, "TMP/BottomCounter");
}
void findDecayProducts(const Particle& mother,
unsigned int& nK0, unsigned int& nKp, unsigned int& nKm) {
for (const Particle & p : mother.children()) {
int id = p.pid();
if ( id == PID::KPLUS ) {
++nKp;
}
else if (id == PID::KMINUS ) {
++nKm;
}
else if (id == PID::K0S) {
++nK0;
}
else if (id == PID::PI0 || id == PID::PIPLUS || id == PID::PIMINUS) {
continue;
}
else if ( !p.children().empty() ) {
findDecayProducts(p, nK0, nKp, nKm);
}
else
continue;
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Loop over bottoms
for (const Particle& bottom : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==521 ||
Cuts::abspid==511)) {
// remove mixing entries etc
for (const Particle & child : bottom.children())
if (child.abspid() == 511 || child.pid()==bottom.pid() ) continue;
_nBottom->fill();
FourMomentum pgamma(0.,0.,0.,0.);
unsigned int ngamma = 0;
for (const Particle & child : bottom.children()) {
if (child.pid() == PID::PHOTON) {
ngamma += 1;
pgamma += child.momentum();
}
}
if (ngamma != 1) continue;
unsigned int nK0(0),nKp(0),nKm(0);
findDecayProducts(bottom, nK0, nKp, nKm);
unsigned int nk = nKp-nKm+nK0;
if (nk % 2 == 1) {
const LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(bottom.momentum().betaVec());
double eGamma = boost.transform(pgamma).E();
_h_spectrum->fill(eGamma);
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
scale(_h_spectrum, 1e4/_nBottom->sumW());
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h_spectrum;
CounterPtr _nBottom;
/// @}
};
RIVET_DECLARE_PLUGIN(BABAR_2008_I769107);
}
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