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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief tau polarization at 197 GeV
class DELPHI_2008_I763352 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(DELPHI_2008_I763352);
/// @name Analysis methods
///@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(ChargedFinalState(), "FS");
declare(UnstableParticles(), "UFS");
// book histos
book(_h_e ,"_t_e " , 20,-1,1);
book(_h_mu ,"_t_mu" , 20,-1,1);
book(_h_pi ,"_t_pi" , 20,-1,1);
book(_h_rho,"_t_rho", 20,-1,1);
}
void findTau(const Particle & p, unsigned int & nprod,
Particles & piP,Particles & pi0, Particles & ell, Particles & nu_ell,
Particles & nu_tau) {
for(const Particle & child : p.children()) {
if(child.pid()==PID::ELECTRON || child.pid()==PID::MUON) {
++nprod;
ell.push_back(child);
}
else if(child.pid()==PID::NU_EBAR || child.pid()==PID::NU_MUBAR) {
++nprod;
nu_ell.push_back(child);
}
else if(child.pid()==PID::PIMINUS) {
++nprod;
piP.push_back(child);
}
else if(child.pid()==PID::PI0) {
++nprod;
pi0.push_back(child);
}
else if(child.pid()==PID::NU_TAU) {
++nprod;
nu_tau.push_back(child);
}
else if(child.pid()==PID::GAMMA)
continue;
else if(child.children().empty() || child.pid()==221 || child.pid()==331) {
++nprod;
}
else {
findTau(child,nprod,piP,pi0,ell,nu_ell,nu_tau);
}
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// require 2 chanrged particles to veto hadronic events
if(apply<ChargedFinalState>(event, "FS").particles().size()!=2) vetoEvent;
// loop over tau leptons
for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==15)) {
unsigned int nprod(0);
Particles piP, pi0, ell, nu_ell, nu_tau;
findTau(p,nprod,piP, pi0, ell, nu_ell, nu_tau);
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
if(nprod==2 && nu_tau.size()==1 && piP.size()==1) {
FourMomentum pPi = boost1.transform(piP[0].momentum());
double cTheta = pPi.p3().unit().dot(p.momentum().p3().unit());
_h_pi->fill(cTheta);
}
else if(nprod==3 && nu_tau.size()==1 && ell.size()==1 && nu_ell.size()==1) {
if(ell[0].pid()==PID::ELECTRON) {
_h_e ->fill(2.*ell[0].momentum().t()/sqrtS());
}
else {
_h_mu->fill(2.*ell[0].momentum().t()/sqrtS());
}
}
else if(nprod==3 && nu_tau.size()==1 && piP.size()==1&& pi0.size()==1) {
FourMomentum pRho = boost1.transform(piP[0].momentum()+pi0[0].momentum());
double cTheta = pRho.p3().unit().dot(p.momentum().p3().unit());
_h_rho->fill(cTheta);
}
}
}
pair<double,double> calcP(Histo1DPtr hist,unsigned int imode) {
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.),bi(0.);
// tau -> pi/rho nu
if(imode==0) {
ai = 0.5*(bin.xMax()-bin.xMin());
bi = 0.5*ai*(bin.xMax()+bin.xMin());
}
// lepton mode
else {
ai = (-5*bin.xMin() + 3*pow(bin.xMin(),3) - pow(bin.xMin(),4) + 5*bin.xMax() - 3*pow(bin.xMax(),3) + pow(bin.xMax(),4))/3.;
bi = ( -bin.xMin() + 3*pow(bin.xMin(),3) - 2*pow(bin.xMin(),4) + bin.xMax() - 3*pow(bin.xMax(),3) + 2*pow(bin.xMax(),4))/3.;
}
double Ei = bin.areaErr();
sum1 += sqr(bi/Ei);
sum2 += bi/sqr(Ei)*(Oi-ai);
}
return make_pair(sum2/sum1,sqrt(1./sum1));
}
/// Normalise histograms etc., after the run
void finalize() {
Scatter2DPtr h_P;
book(h_P,1,1,1);
normalize(_h_e);
pair<double,double> P_e = calcP(_h_e,1);
double s1 = P_e.first/sqr(P_e.second);
double s2 = 1./sqr(P_e.second);
normalize(_h_mu);
pair<double,double> P_mu = calcP(_h_mu,1);
s1 += P_mu.first/sqr(P_mu.second);
s2 += 1./sqr(P_mu.second);
normalize(_h_pi);
pair<double,double> P_pi = calcP(_h_pi,0);
s1 += P_pi.first/sqr(P_pi.second);
s2 += 1./sqr(P_pi.second);
normalize(_h_rho);
pair<double,double> P_rho = calcP(_h_rho,0);
s1 += P_rho.first/sqr(P_rho.second);
s2 += 1./sqr(P_rho.second);
P_rho.first /=0.46;
P_rho.second /=0.46;
// average
pair<double,double> P_aver = make_pair(s1/s2,sqrt(1./s2));
h_P->addPoint(0.5,P_aver.first, make_pair(0.5,0.5),
make_pair(P_aver.second,P_aver.second));
}
///@}
/// @name Histograms
///@{
Histo1DPtr _h_e,_h_mu,_h_pi,_h_rho;
///@}
};
RIVET_DECLARE_PLUGIN(DELPHI_2008_I763352);
}
|