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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Tools/BinnedHistogram.hh"
namespace Rivet {
/// @brief rho+/- and omega polarization
class OPAL_2000_I502750 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_2000_I502750);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(Beam(), "Beams");
declare(ChargedFinalState(), "FS");
declare(UnstableParticles(), "UFS");
// Book histograms
{Histo1DPtr temp; _h_ctheta_rho .add(0.025,0.05,book(temp, "ctheta_rho_0",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_rho .add(0.05 ,0.1 ,book(temp, "ctheta_rho_1",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_rho .add(0.1 ,0.15,book(temp, "ctheta_rho_2",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_rho .add(0.15 ,0.3 ,book(temp, "ctheta_rho_3",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_rho .add(0.3 ,0.6 ,book(temp, "ctheta_rho_4",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_omega.add(0.025,0.05,book(temp, "ctheta_omega_0",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_omega.add(0.05 ,0.1 ,book(temp, "ctheta_omega_1",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_omega.add(0.1 ,0.15,book(temp, "ctheta_omega_2",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_omega.add(0.15 ,0.3 ,book(temp, "ctheta_omega_3",20,-1.,1.));}
{Histo1DPtr temp; _h_ctheta_omega.add(0.3 ,0.6 ,book(temp, "ctheta_omega_4",20,-1.,1.));}
book(_h_ctheta_omega_all, "ctheta_omega_all",20,-1.,1.);
}
pair<double,double> calcRho(Histo1DPtr hist) {
if(hist->numEntries()==0.) return make_pair(0.,0.);
double sum1(0.),sum2(0.);
for (auto bin : hist->bins() ) {
double Oi = bin.area();
if(Oi==0.) continue;
double ai = 0.25*(bin.xMax()*(3.-sqr(bin.xMax())) - bin.xMin()*(3.-sqr(bin.xMin())));
double bi = 0.75*(bin.xMin()*(1.-sqr(bin.xMin())) - bin.xMax()*(1.-sqr(bin.xMax())));
double Ei = bin.areaErr();
sum1 += sqr(bi/Ei);
sum2 += bi/sqr(Ei)*(Oi-ai);
}
return make_pair(sum2/sum1,sqrt(1./sum1));
}
bool findOmegaDecay(Particle omega,Particles & pi0, Particles & pip, Particles & pim) {
for(const Particle & child : omega.children()) {
if(child.pid()==211)
pip.push_back(child);
else if(child.pid()==-211)
pim.push_back(child);
else if(child.pid()==111)
pi0.push_back(child);
else if(!child.children().empty()) {
if(!findOmegaDecay(child,pi0,pip,pim)) return false;
}
else
return false;
}
return true;
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// First, veto on leptonic events by requiring at least 4 charged FS particles
const FinalState& fs = apply<FinalState>(event, "FS");
const size_t numParticles = fs.particles().size();
// Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
if (numParticles < 2) {
MSG_DEBUG("Failed leptonic event cut");
vetoEvent;
}
MSG_DEBUG("Passed leptonic event cut");
// Get beams and average beam momentum
const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
const double meanBeamMom = ( beams.first.p3().mod() +
beams.second.p3().mod() ) / 2.0;
MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
// loop over rho and omega mesons
const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
for (const Particle& p : ufs.particles(Cuts::abspid==213 || Cuts::abspid==223)) {
double xE = p.momentum().t()/meanBeamMom;
Vector3 e1z = p.momentum().p3().unit();
LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
if(p.abspid()==213) {
if(p.children().size()!=2) continue;
int sign = p.pid()/213;
Particle pion;
if(p.children()[0].pid()==sign*211 && p.children()[1].pid()==111) {
pion = p.children()[0];
}
else if(p.children()[1].pid()==sign*211 && p.children()[0].pid()==111) {
pion = p.children()[1];
}
else
continue;
Vector3 axis1 = boost.transform(pion.momentum()).p3().unit();
double ctheta = e1z.dot(axis1);
_h_ctheta_rho.fill(xE,ctheta);
}
else {
Particles pi0,pip,pim;
bool three_pi = findOmegaDecay(p,pi0,pip,pim);
if(!three_pi || pi0.size()!=1 || pip.size()!=1 || pim.size()!=1)
continue;
Vector3 v1 = boost.transform(pi0[0].momentum()).p3().unit();
Vector3 v2 = boost.transform(pip[0].momentum()).p3().unit();
Vector3 norm = v1.cross(v2).unit();
double ctheta = e1z.dot(norm);
_h_ctheta_omega.fill(xE,ctheta);
if(xE>0.025) _h_ctheta_omega_all->fill(ctheta);
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
vector<double> x = {0.025,0.05,0.1,0.15,0.3,0.6};
Scatter2DPtr h_rho ;
book(h_rho, 1,1,1);
Scatter2DPtr h_omega;
book(h_omega, 2,1,1);
for(unsigned int ix=0;ix<_h_ctheta_rho.histos().size();++ix) {
// rho
normalize(_h_ctheta_rho.histos()[ix]);
pair<double,double> rho00 = calcRho(_h_ctheta_rho.histos()[ix]);
h_rho->addPoint(0.5*(x[ix]+x[ix+1]), rho00.first, make_pair(0.5*(x[ix+1]-x[ix]),0.5*(x[ix+1]-x[ix])),
make_pair(rho00.second,rho00.second) );
// omega
normalize(_h_ctheta_omega.histos()[ix]);
rho00 = calcRho(_h_ctheta_omega.histos()[ix]);
h_omega->addPoint(0.5*(x[ix]+x[ix+1]), rho00.first, make_pair(0.5*(x[ix+1]-x[ix]),0.5*(x[ix+1]-x[ix])),
make_pair(rho00.second,rho00.second) );
}
// omega over whole range
Scatter2DPtr h_omega_all;
book(h_omega_all,2,2,1);
normalize(_h_ctheta_omega_all);
pair<double,double> rho00 = calcRho(_h_ctheta_omega_all);
h_omega_all->addPoint(0.5125, rho00.first, make_pair(0.4875,0.4875),
make_pair(rho00.second,rho00.second) );
}
//@}
/// @name Histograms
//@{
BinnedHistogram _h_ctheta_rho,_h_ctheta_omega;
Histo1DPtr _h_ctheta_omega_all;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(OPAL_2000_I502750);
}
|