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113 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief D_s+ -> pi+pi+pi-
class BESIII_2021_I1909391 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1909391);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
UnstableParticles ufs = UnstableParticles(Cuts::abspid==431);
declare(ufs, "UFS");
DecayedParticles DS(ufs);
DS.addStable(PID::PI0);
DS.addStable(PID::K0S);
declare(DS,"DS");
// histos
book(_h_pippim[0],1,1,1);
book(_h_pippip ,1,1,2);
book(_h_pippim[1],1,1,3);
book(_h_pippim[2],1,1,4);
book(_dalitz, "dalitz",50,0.,3.5,50,0.0,3.5);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// parameters from the efficiency function, table 1 in paper
static const double E1 = 0.064;
static const double E2 = -0.066;
static const double E3 = -0.006;
static const double E11 = -0.158;
static const double E12 = 0.090;
static const double Eth[3] = {1.516,1.516,1.563};
static const map<PdgId,unsigned int> & mode = { { 211,2}, {-211,1}};
static const map<PdgId,unsigned int> & modeCC = { {-211,2}, { 211,1}};
DecayedParticles DS = apply<DecayedParticles>(event, "DS");
// loop over particles
for(unsigned int ix=0;ix<DS.decaying().size();++ix) {
int sign = 1;
if (DS.decaying()[ix].pid()>0 && DS.modeMatches(ix,3,mode)) {
sign=1;
}
else if (DS.decaying()[ix].pid()<0 && DS.modeMatches(ix,3,modeCC)) {
sign=-1;
}
else
continue;
const Particles & pip = DS.decayProducts()[ix].at( sign*211);
const Particle & pim = DS.decayProducts()[ix].at(-sign*211)[0];
// kinematic variables
double x[3] = {(pim.momentum()+pip[0].momentum()).mass2(),
(pim.momentum()+pip[1].momentum()).mass2(),
(pip[0].momentum()+pip[1].momentum()).mass2()};
if(x[0]>x[1]) swap(x[0],x[1]);
_dalitz->fill(x[0],x[1]);
_dalitz->fill(x[1],x[0]);
// calculate the efficiency
double xh = x[0]-1.,yh=x[1]-1.;
double eff = (1.+E1*(xh+yh)+E2*(sqr(xh)+sqr(yh))+E3*(pow(xh,3)+pow(yh,3))
+E11*xh*yh+E12*xh*yh*(xh+yh));
double xmax = sqr(DS.decaying()[ix].mass()-pip[0].mass());
double T=1.;
for(unsigned int ix=0;ix<3;++ix) {
double arg = Eth[ix]*abs(x[ix]-xmax);
if(arg<0.5*M_PI) T *=sin(arg);
}
eff *=T;
// fill plots
_h_pippim[0]->fill(x[0],eff);
_h_pippim[0]->fill(x[1],eff);
_h_pippim[1]->fill(x[0],eff);
_h_pippim[2]->fill(x[1],eff);
_h_pippip ->fill(x[2],eff);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<3;++ix)
normalize(_h_pippim[ix]);
normalize(_h_pippip);
normalize(_dalitz);
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h_pippim[3],_h_pippip;
Histo2DPtr _dalitz;
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2021_I1909391);
}
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