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104 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"
namespace Rivet {
/// @brief B_c - > jpsi pi+ and pi+pi+pi-
class LHCB_2012_I1097092 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2012_I1097092);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
UnstableParticles ufs = UnstableParticles(Cuts::abspid==541);
declare(ufs, "UFS");
DecayedParticles BC(ufs);
BC.addStable( PID::PI0);
BC.addStable( PID::K0S);
BC.addStable( PID::JPSI);
declare(BC, "BC");
for(unsigned int ix=0;ix<2;++ix) {
book(_h_mass [ix],1+ix,1,1);
book(_h_ctheta[ix],3,1,1+ix);
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const map<PdgId,unsigned int> & mode1 = { { 443,1}, { 211,1} };
static const map<PdgId,unsigned int> & mode1CC = { { 443,1}, {-211,1} };
static const map<PdgId,unsigned int> & mode2 = { { 443,1}, { 211,2}, {-211,1} };
static const map<PdgId,unsigned int> & mode2CC = { { 443,1}, {-211,2}, { 211,1} };
DecayedParticles BC = apply<DecayedParticles>(event, "BC");
// loop over particles
for(unsigned int ix=0;ix<BC.decaying().size();++ix) {
int sign = BC.decaying()[ix].pid()/BC.decaying()[ix].abspid();
int imode=-1;
if ((sign== 1 && BC.modeMatches(ix,2,mode1 )) ||
(sign==-1 && BC.modeMatches(ix,2,mode1CC))) {
imode=0;
}
else if ((sign== 1 && BC.modeMatches(ix,4,mode2 )) ||
(sign==-1 && BC.modeMatches(ix,4,mode2CC))) {
const Particle & pim = BC.decayProducts()[ix].at(-sign*211)[0];
const Particles & pip = BC.decayProducts()[ix].at( sign*211);
_h_mass[0]->fill((pim.momentum()+pip[0].momentum()+pip[1].momentum()).mass());
_h_mass[1]->fill((pim.momentum()+pip[0].momentum()).mass());
_h_mass[1]->fill((pim.momentum()+pip[1].momentum()).mass());
imode=1;
}
else
continue;
// check the J/psi decay mode
const Particle & jpsi = BC.decayProducts()[ix].at(443)[0];
if(jpsi.children().size()!=2 || jpsi.children()[0].pid()!=-jpsi.children()[1].pid() ||
jpsi.children()[0].abspid()!=13) continue;
Particle muon = jpsi.children()[0].pid()==13 ? jpsi.children()[0] : jpsi.children()[1];
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(BC.decaying()[ix].momentum().betaVec());
FourMomentum pJPsi = boost1.transform(jpsi.momentum());
FourMomentum pMu = boost1.transform(muon.momentum());
// to j/psi rest frame
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pJPsi.betaVec());
Vector3 axis = pJPsi.p3().unit();
FourMomentum pp = boost2.transform(pMu);
// calculate angle
double cTheta = pp.p3().unit().dot(axis);
_h_ctheta[imode]->fill(cTheta);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<2;++ix) {
normalize(_h_mass [ix]);
normalize(_h_ctheta[ix]);
}
}
/// @}
/// @name Histograms
/// @{
Histo1DPtr _h_mass[2];
Histo1DPtr _h_ctheta[2];
/// @}
};
RIVET_DECLARE_PLUGIN(LHCB_2012_I1097092);
}
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