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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief D_s1 decay angles
class BABAR_2011_I892421 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2011_I892421);
/// @name Analysis methods
///@{
/// Book histograms and initialise projections before the run
void init() {
// projections
declare(UnstableParticles(), "UFS");
// book histos
book(_h_cP,1,1,1);
book(_h_c ,2,1,1);
}
bool isK0(int id) {
return id==310 || id==130 || abs(id)==311;
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const int DsID = 10433;
const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
for (const Particle& p : ufs.particles(Cuts::abspid==DsID)) {
// decay angle
int sign = p.pid()/DsID;
Particle Dstar;
if(p.children().size()!=2) continue;
if(p.children()[0].pid()==sign*413 &&
isK0(p.children()[1].pid())) {
Dstar = p.children()[0];
}
else if(p.children()[1].pid()==sign*413 &&
isK0(p.children()[0].pid())) {
Dstar = p.children()[1];
}
else {
continue;
}
// first boost to the D_s1 rest frame
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
FourMomentum pDstar = boost1.transform(Dstar.momentum());
double cTheta = pDstar.p3().unit().dot(p.momentum().p3().unit());
_h_c->fill(cTheta);
if(Dstar.children().size()!=2) continue;
Particle D0;
if(Dstar.children()[0].pid()== sign*211 &&
Dstar.children()[1].pid()== sign*421) {
D0 = Dstar.children()[1];
}
else if(Dstar.children()[1].pid()== sign*211 &&
Dstar.children()[0].pid()== sign*421) {
D0 = Dstar.children()[0];
}
else
continue;
// boost to D_s frame
FourMomentum pD = boost1.transform(D0.momentum());
// to D* rest frame
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDstar.betaVec());
Vector3 axis = pDstar.p3().unit();
FourMomentum pp = boost2.transform(pD);
// calculate angle
double cThetap = pp.p3().unit().dot(axis);
_h_cP->fill(cThetap);
}
}
/// Normalise histograms etc., after the run
void finalize() {
normalize(_h_cP);
normalize(_h_c );
}
///@}
/// @name Histograms
///@{
Histo1DPtr _h_cP,_h_c;
///@}
};
RIVET_DECLARE_PLUGIN(BABAR_2011_I892421);
}
|