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| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/Beam.hh"
namespace Rivet {
/// @brief Collins assymmetry
class BESIII_2016_I1384778 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2016_I1384778);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
declare(Beam(), "Beams");
declare(FinalState(Cuts::abspid==PID::PIPLUS), "FS");
// book the histograms
_h_L = vector<Histo1DPtr>(6,Histo1DPtr());
_h_U = vector<Histo1DPtr>(6,Histo1DPtr());
_h_C = vector<Histo1DPtr>(6,Histo1DPtr());
for(unsigned int ix=0;ix<6;++ix) {
std::ostringstream title;
title << "/TMP/h_z1z2_" << ix+1;
book(_h_L[ix],title.str()+"_L",20,0.,M_PI);
book(_h_U[ix],title.str()+"_U",20,0.,M_PI);
book(_h_C[ix],title.str()+"_C",20,0.,M_PI);
}
double xbin[6]={0.,.2,.3,.45,.8,1.4};
for(unsigned int ix=0;ix<5;++ix) {
std::ostringstream title;
title << "/TMP/h_pT_" << ix+1;
Histo1DPtr hL,hU,hC;
book(hL,title.str()+"_L",20,0.,M_PI);
_h_pT_L.add(xbin[ix],xbin[ix+1], hL);
book(hU,title.str()+"_U",20,0.,M_PI);
_h_pT_U.add(xbin[ix],xbin[ix+1], hU);
book(hC,title.str()+"_C",20,0.,M_PI);
_h_pT_C.add(xbin[ix],xbin[ix+1], hC);
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// get the axis, direction of incoming electron
const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
Vector3 axis;
if(beams.first.pid()>0)
axis = beams.first .momentum().p3().unit();
else
axis = beams.second.momentum().p3().unit();
// loop over pions pair, using index to avoid double counting
Particles pions = apply<FinalState>(event, "FS").particles();
for(unsigned int i1=0;i1<pions.size();++i1) {
const double x1=2.*pions[i1].momentum().t()/sqrtS();
// cut on z1
if(x1<0.2||x1>0.9) continue;
// cos theta cut
if(abs(cos(pions[i1].momentum().p3().polarAngle()))>0.93) continue;
for(unsigned int i2=i1+1;i2<pions.size();++i2) {
// cut on z2
const double x2=2.*pions[i2].momentum().t()/sqrtS();
if(x2<0.2||x2>0.9) continue;
// cos theta cut
if(abs(cos(pions[i2].momentum().p3().polarAngle()))>0.93) continue;
// cut on opening angle (>120 degrees)
if(pions[i1].momentum().p3().angle(pions[i2].momentum().p3())>2.*M_PI/3.)
continue;
Particle p1=pions[i1], p2=pions[i2];
double z1(x1),z2(x2);
// randomly order the particles
if(rand()/static_cast<double>(RAND_MAX) < 0.5 ) {
swap(p1,p2);
swap(z1,z2);
}
// particle 2 defines the z axis
Vector3 ez = p2.momentum().p3().unit();
// beam and 2 define the plane (y is normal to plane)
Vector3 ey = ez.cross(axis).unit();
// x by cross product
Vector3 ex = ey.cross(ez).unit();
// phi
double phi = ex.angle(p1.momentum().p3());
// hists vs z1,z2
unsigned int ibin=0;
if(z1<=.3&&z2<=.3) {
ibin=0;
}
else if(z1>0.5&&z2>0.5) {
ibin=5;
}
else if(min(z1,z2)<=0.3) {
if(max(z1,z2)>0.5)
ibin=2;
else
ibin=1;
}
else {
if(max(z1,z2)>0.5)
ibin=4;
else
ibin=3;
}
_h_C[ibin]->fill(phi);
if(p1.pid()==p2.pid())
_h_L[ibin]->fill(phi);
else
_h_U[ibin]->fill(phi);
// hists vs pT
double pPar2 = sqr(ez.dot(p1.momentum().p3()));
double pPerp = sqrt(p1.momentum().p3().mod2()-pPar2);
_h_pT_C.fill(pPerp,phi);
if(p1.pid()==p2.pid())
_h_pT_L.fill(pPerp,phi);
else
_h_pT_U.fill(pPerp,phi);
}
}
}
pair<double,double> calcAsymmetry(Scatter2DPtr hist) {
double sum1(0.),sum2(0.);
for (auto point : hist->points() ) {
double Oi = point.y();
if(Oi==0. || std::isnan(Oi) ) continue;
double ai = 1.;
double bi = 0.5*(sin(2.*point.xMax())-sin(2.*point.xMin()))/(point.xMax()-point.xMin());
double Ei = point.yErrAvg();
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() {
// ratios
Scatter2DPtr _h_z_UL,_h_z_UC;
book(_h_z_UL,1,1,5);
book(_h_z_UC,1,1,6);
for(unsigned int ix=0;ix<6;++ix) {
normalize(_h_L[ix]);
normalize(_h_U[ix]);
normalize(_h_C[ix]);
std::ostringstream title;
title << "/TMP/R_z1z2_" << ix+1;
Scatter2DPtr R1;
book(R1,title.str()+"_UL");
divide(_h_U[ix],_h_L[ix],R1);
Scatter2DPtr R2;
book(R2,title.str()+"_UC");
divide(_h_U[ix],_h_C[ix],R2);
pair<double,double> asym1 = calcAsymmetry(R1);
_h_z_UL->addPoint(double(ix)+1., asym1.first, make_pair(0.5,0.5),
make_pair(asym1.second,asym1.second) );
pair<double,double> asym2 = calcAsymmetry(R2);
_h_z_UC->addPoint(double(ix)+1., asym2.first, make_pair(0.5,0.5),
make_pair(asym2.second,asym2.second) );
}
Scatter2DPtr _h_pT_UL,_h_pT_UC;
book(_h_pT_UL,2,1,4);
book(_h_pT_UC,2,1,5);
Scatter2D temphisto(refData(2, 1, 4));
for(unsigned int ix=0;ix<5;++ix) {
normalize(_h_pT_L.histos()[ix]);
normalize(_h_pT_U.histos()[ix]);
normalize(_h_pT_C.histos()[ix]);
std::ostringstream title;
title << "/TMP/R_pT_" << ix+1;
Scatter2DPtr R1;
book(R1,title.str()+"_UL");
divide(_h_U[ix],_h_L[ix],R1);
Scatter2DPtr R2;
book(R2,title.str()+"_UC");
divide(_h_U[ix],_h_C[ix],R2);
const double x = temphisto.point(ix).x();
pair<double,double> ex = temphisto.point(ix).xErrs();
pair<double,double> asym1 = calcAsymmetry(R1);
_h_pT_UL->addPoint(x, asym1.first, ex,
make_pair(asym1.second,asym1.second) );
pair<double,double> asym2 = calcAsymmetry(R2);
_h_pT_UC->addPoint(x, asym2.first, ex,
make_pair(asym2.second,asym2.second) );
}
}
//@}
/// @name Histograms
//@{
vector<Histo1DPtr> _h_L,_h_U,_h_C;
BinnedHistogram _h_pT_L,_h_pT_U,_h_pT_C;
//@}
};
RIVET_DECLARE_PLUGIN(BESIII_2016_I1384778);
}
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