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Rivet analyses reference
BABAR_2012_I1125973
Semi-leptonic $B$ to $\pi$, $\omega$ and $\eta$ decays
Experiment: BABAR (PEP-II)
Inspire ID: 1125973
Status: VALIDATED NOHEPDATA
Authors:
References:
- Phys.Rev.D 86 (2012) 092004
Beams: * *
Beam energies: ANY
Run details:
- Any process producing B+ or B0, original e+e->Upsilon(4S)
Implementation of Lorentz invariant $q^2$ distributions ("form factor") for semileptonic $B^0$ and $B^+$ decays. Includes $\pi$, $\omega$ and $\eta$ decays.
Source code:
BABAR_2012_I1125973.cc
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110 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief B -> pi, eta and omega decays
class BABAR_2012_I1125973 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2012_I1125973);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(Cuts::pid==PID::BPLUS || Cuts::pid==PID::B0), "UFS");
// histograms
for(unsigned int ix=0;ix<2;++ix) {
book(_h_B0_pi[ix], 1, 1, ix+1);
book(_h_Bp_pi[ix], 2, 1, ix+1);
book(_nB[ix],"TMP/nB_"+toString(ix+1));
}
book(_h_omega,3,1,1);
book(_h_eta ,4,1,1);
}
// Calculate the Q2 using mother and daughter charged lepton
double q2(const Particle& B, int mesonID) {
FourMomentum q = B.mom() - filter_select(B.children(), Cuts::pid==mesonID)[0];
return q*q;
}
// Check for explicit decay into pdgids
bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
// Trivial check to ignore any other decays but the one in question modulo photons
const Particles children = mother.children(Cuts::pid!=PID::PHOTON);
if (children.size()!=ids.size()) return false;
// Check for the explicit decay
return all(ids, [&](int i){return count(children, hasPID(i))==1;});
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Get B+ Mesons
for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
if( p.pid()==PID::B0) {
_nB[0]->fill();
if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E}) ||
isSemileptonicDecay(p, {PID::PIMINUS, PID::ANTIMUON, PID::NU_MU})) {
double Q2 = q2(p,PID::PIMINUS);
_h_B0_pi[0]->fill(Q2);
_h_B0_pi[1]->fill(Q2);
}
}
else {
_nB[1]->fill();
if (isSemileptonicDecay(p, {PID::PI0, PID::POSITRON, PID::NU_E}) ||
isSemileptonicDecay(p, {PID::PI0, PID::ANTIMUON, PID::NU_MU})) {
double Q2 = q2(p,PID::PI0);
_h_Bp_pi[0]->fill(Q2);
_h_Bp_pi[1]->fill(Q2);
}
else if (isSemileptonicDecay(p, {PID::OMEGA, PID::POSITRON, PID::NU_E}) ||
isSemileptonicDecay(p, {PID::OMEGA, PID::ANTIMUON, PID::NU_MU})) {
_h_omega->fill(q2(p,PID::OMEGA));
}
else if (isSemileptonicDecay(p, {PID::ETA, PID::POSITRON, PID::NU_E}) ||
isSemileptonicDecay(p, {PID::ETA, PID::ANTIMUON, PID::NU_MU})) {
_h_eta->fill(q2(p,PID::ETA));
}
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
// BR in units of 10^{-7}
for(unsigned int ix=0;ix<2;++ix) {
scale(_h_B0_pi[ix], 1e7/ *_nB[0]);
scale(_h_Bp_pi[ix], 1e7/ *_nB[1]);
}
scale(_h_omega,1e7/ *_nB[1]);
scale(_h_eta ,1e7/ *_nB[1]);
}
/// @}
/// @name Histograms
/// @{
CounterPtr _nB[2];
Histo1DPtr _h_B0_pi[2],_h_Bp_pi[2],_h_omega,_h_eta;
/// @}
};
RIVET_DECLARE_PLUGIN(BABAR_2012_I1125973);
}
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