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156 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief Bbar0 -> D*+ semileptonic
class BELLE_2017_I1512299 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2017_I1512299);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS");
// Book histograms
book(_h_w , 1, 1, 1);
book(_h_costhv, 2, 1, 1);
book(_h_costhl, 3, 1, 1);
book(_h_chi , 4, 1, 1);
}
/// Perform the per-event analysis
bool analyzeDecay(Particle mother, vector<int> ids) {
// There is no point in looking for decays with less particles than to be analysed
if (mother.children().size() == ids.size()) {
bool decayfound = true;
for (int id : ids) {
if (!contains(mother, id)) decayfound = false;
}
return decayfound;
}
return false;
}
bool contains(Particle& mother, int id) {
return any(mother.children(), HasPID(id));
}
double recoilW(const Particle& mother) {
FourMomentum lepton, neutrino, meson, q;
for(const Particle& c : mother.children()) {
if (c.isNeutrino()) neutrino=c.mom();
if (c.isLepton() && !c.isNeutrino()) lepton =c.mom();
if (c.isHadron()) meson=c.mom();
}
q = lepton + neutrino; //no hadron before
double mb2= mother.mom()*mother.mom();
double mD2 = meson*meson;
return (mb2 + mD2 - q*q )/ (2. * sqrt(mb2) * sqrt(mD2) );
}
/// Perform the per-event analysis
void analyze(const Event& event) {
FourMomentum pl, pnu, pB, pD, pDs, ppi;
// Iterate of B0bar mesons
for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==-511)) {
pB = p.momentum();
// Find semileptonic decays
if (analyzeDecay(p, {PID::DSTARPLUS,-12,11}) || analyzeDecay(p, {PID::DSTARPLUS,-14,13}) ) {
_h_w->fill(recoilW(p));
// Get the necessary momenta for the angles
bool foundDdecay=false;
for (const Particle & c : p.children()) {
if ( (c.pid() == PID::DSTARPLUS) && (analyzeDecay(c, {PID::PIPLUS, PID::D0}) || analyzeDecay(c, {PID::PI0, PID::DPLUS})) ) {
foundDdecay=true;
pDs = c.momentum();
for (const Particle & dc : c.children()) {
if (dc.hasCharm()) pD = dc.momentum();
else ppi = dc.momentum();
}
}
if (c.pid() == 11 || c.pid() == 13) pl = c.momentum();
if (c.pid() == -12 || c.pid() == -14) pnu = c.momentum();
}
// This is the angle analysis
if (foundDdecay) {
// First boost all relevant momenta into the B-rest frame
const LorentzTransform B_boost = LorentzTransform::mkFrameTransformFromBeta(pB.betaVec());
// Momenta in B rest frame
FourMomentum lv_brest_Dstar = B_boost.transform(pDs);
FourMomentum lv_brest_w = B_boost.transform(pB - pDs);
FourMomentum lv_brest_D = B_boost.transform(pD);
FourMomentum lv_brest_lep = B_boost.transform(pl);
const LorentzTransform Ds_boost = LorentzTransform::mkFrameTransformFromBeta(lv_brest_Dstar.betaVec());
FourMomentum lv_Dstarrest_D = Ds_boost.transform(lv_brest_D);
const LorentzTransform W_boost = LorentzTransform::mkFrameTransformFromBeta(lv_brest_w.betaVec());
FourMomentum lv_wrest_lep = W_boost.transform(lv_brest_lep);
double cos_thetaV = cos(lv_brest_Dstar.p3().angle(lv_Dstarrest_D.p3()));
_h_costhv->fill(cos_thetaV);
double cos_thetaL = cos(lv_brest_w.p3().angle(lv_wrest_lep.p3()));
_h_costhl->fill(cos_thetaL);
Vector3 LTrans = lv_wrest_lep.p3() - cos_thetaL*lv_wrest_lep.p3().perp()*lv_brest_w.p3().unit();
Vector3 VTrans = lv_Dstarrest_D.p3() - cos_thetaV*lv_Dstarrest_D.p3().perp()*lv_brest_Dstar.p3().unit();
float chi = atan2(LTrans.cross(VTrans).dot(lv_brest_w.p3().unit()), LTrans.dot(VTrans));
if(chi < 0) chi += TWOPI;
_h_chi->fill(chi);
}
}
}
}
//else if (analyzeDecay(p, {413,-14,13}) ) {
//_h_w->fill(recoilW(p));
//}
/// Normalise histograms etc., after the run
void finalize() {
double GAMMA_B0 = 4.32e-13; // Total width in GeV, calculated from mean life time of 1.52 pico seconds
double BR_B0_DSPLUS_ELL_NU = 0.0495; // Branching fraction from the same paper for B0bar to D*+ ell nu
double NORM = GAMMA_B0 * BR_B0_DSPLUS_ELL_NU; // Normalise histos to partial width
normalize(_h_w, NORM);
normalize(_h_costhv, NORM);
normalize(_h_costhl, NORM);
normalize(_h_chi, NORM);
}
//@}
/// @name Histograms
//@{
Histo1DPtr _h_w;
Histo1DPtr _h_costhv;
Histo1DPtr _h_costhl;
Histo1DPtr _h_chi;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(BELLE_2017_I1512299);
}
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