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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Tools/BinnedHistogram.hh"
namespace Rivet {
/// @brief D*+ polarization
class CLEO_1991_I314060 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_1991_I314060);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(Beam(), "Beams");
declare(UnstableParticles(), "UFS");
{Histo1DPtr temp; _h_ctheta.add(0.25,0.45,book(temp,2,1,1));}
{Histo1DPtr temp; _h_ctheta.add(0.45,0.55,book(temp,2,1,2));}
{Histo1DPtr temp; _h_ctheta.add(0.55,0.65,book(temp,2,1,3));}
{Histo1DPtr temp; _h_ctheta.add(0.65,0.75,book(temp,2,1,4));}
{Histo1DPtr temp; _h_ctheta.add(0.75,0.85,book(temp,2,1,5));}
{Histo1DPtr temp; _h_ctheta.add(0.85,1.00,book(temp,2,1,6));}
}
/// Recursively walk the decay tree to find decay products of @a p
void findDecayProducts(Particle mother, Particles & d0, Particles & pi,unsigned int & ncount) {
for(const Particle & p: mother.children()) {
if(p.abspid()==421)
d0.push_back(p);
else if(p.abspid()==211)
pi.push_back(p);
ncount +=1;
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// 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 D*+ mesons
const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
for (const Particle& p: ufs.particles(Cuts::abspid==413)) {
// calc x+
double x = (p.momentum().E()+p.momentum().z())/(meanBeamMom + sqrt(sqr(meanBeamMom)+p.mass2()));
// checck decay products
Particles d0,pi;
unsigned int ncount=0;
findDecayProducts(p,d0, pi,ncount);
if(ncount!=2 || pi.size()!=1 || d0.size()!=1 ) continue;
if(pi[0].pid()/p.pid()<0) continue;
LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
Vector3 d1 = boost.transform(pi[0].momentum()).p3().unit();
double ctheta = d1.dot(p.momentum().p3().unit());
_h_ctheta.fill(x,ctheta);
}
}
pair<double,pair<double,double> > calcAlpha(Histo1DPtr hist) {
if(hist->numEntries()==0.) return make_pair(0.,make_pair(0.,0.));
double sum1(0.),sum2(0.),sum3(0.),sum4(0.),sum5(0.);
for (auto bin : hist->bins() ) {
double Oi = bin.area();
if(Oi==0.) continue;
double a = 1.5*(bin.xMax() - bin.xMin());
double b = 0.5*(pow(bin.xMax(),3) - pow(bin.xMin(),3));
double Ei = bin.areaErr();
sum1 += a*Oi/sqr(Ei);
sum2 += b*Oi/sqr(Ei);
sum3 += sqr(a)/sqr(Ei);
sum4 += sqr(b)/sqr(Ei);
sum5 += a*b/sqr(Ei);
}
// calculate alpha
double alpha = (-3*sum1 + 9*sum2 + sum3 - 3*sum5)/(sum1 - 3*sum2 + 3*sum4 - sum5);
// and error
double cc = -pow((sum3 + 9*sum4 - 6*sum5),3);
double bb = -2*sqr(sum3 + 9*sum4 - 6*sum5)*(sum1 - 3*sum2 + 3*sum4 - sum5);
double aa = sqr(sum1 - 3*sum2 + 3*sum4 - sum5)*(-sum3 - 9*sum4 + sqr(sum1 - 3*sum2 + 3*sum4 - sum5) + 6*sum5);
double dis = sqr(bb)-4.*aa*cc;
if(dis>0.) {
dis = sqrt(dis);
return make_pair(alpha,make_pair(0.5*(-bb+dis)/aa,-0.5*(-bb-dis)/aa));
}
else {
return make_pair(alpha,make_pair(0.,0.));
}
}
/// Normalise histograms etc., after the run
void finalize() {
vector<double> x = {0.35,0.5 ,0.6 ,0.7 ,0.8 ,0.925};
vector<double> wid = {0.10,0.05,0.05,0.05,0.05,0.075};
Scatter2DPtr h_alpha;
book(h_alpha,1,1,1);
Scatter2DPtr h_rho ;
book(h_rho ,1,1,2);
Scatter2DPtr h_eta ;
book(h_eta ,1,1,3);
for(unsigned int ix=0;ix<_h_ctheta.histos().size();++ix) {
// normalize
normalize(_h_ctheta.histos()[ix]);
// alpha
pair<double,pair<double,double> > alpha = calcAlpha(_h_ctheta.histos()[ix]);
h_alpha->addPoint(x[ix], alpha.first, make_pair(wid[ix],wid[ix]),alpha.second);
// rho
double rho = (1.+alpha.first)/(3.+alpha.first);
pair<double,double> rho_error;
rho_error.first = 2.*alpha.second.first /sqr(3.+alpha.first);
rho_error.second = 2.*alpha.second.second/sqr(3.+alpha.first);
h_rho->addPoint(x[ix], rho, make_pair(wid[ix],wid[ix]),rho_error);
// eta
double eta = alpha.first/(3.+alpha.first);
pair<double,double> eta_error;
eta_error.first = 3.*alpha.second.first /sqr(3.+alpha.first);
eta_error.second = 3.*alpha.second.second/sqr(3.+alpha.first);
h_eta->addPoint(x[ix], eta, make_pair(wid[ix],wid[ix]),eta_error);
}
}
//@}
/// @name Histograms
//@{
BinnedHistogram _h_ctheta;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(CLEO_1991_I314060);
}
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