V0Filter.cc

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#include <cmath>

#include <Math/GenVector/PxPyPzM4D.h>
#include "DataFormats/BTauReco/interface/ParticleMasses.h"
#include "DataFormats/Math/interface/LorentzVector.h"
#include "RecoBTag/SecondaryVertex/interface/V0Filter.h"

using namespace reco; 

V0Filter::V0Filter(const edm::ParameterSet &params) :
    k0sMassWindow(params.getParameter<double>("k0sMassWindow"))
{
}

bool
V0Filter::operator () (const reco::Track *const *tracks, unsigned int n) const
{
    // only check for K0s for now

    if (n != 2)
        return true;

    if (tracks[0]->charge() * tracks[1]->charge() > 0)
        return true;

    ROOT::Math::LorentzVector<ROOT::Math::PxPyPzM4D<double> > vec1;
    ROOT::Math::LorentzVector<ROOT::Math::PxPyPzM4D<double> > vec2;

    vec1.SetPx(tracks[0]->px());
    vec1.SetPy(tracks[0]->py());
    vec1.SetPz(tracks[0]->pz());
    vec1.SetM(ParticleMasses::piPlus);

    vec2.SetPx(tracks[1]->px());
    vec2.SetPy(tracks[1]->py());
    vec2.SetPz(tracks[1]->pz());
    vec2.SetM(ParticleMasses::piPlus);

    double invariantMass = (vec1 + vec2).M();
    if (std::abs(invariantMass - ParticleMasses::k0) < k0sMassWindow)
        return false;

    return true;
}

bool
V0Filter::operator () (const reco::TrackRef *tracks, unsigned int n) const
{
    std::vector<const reco::Track*> trackPtrs(n);
    for(unsigned int i = 0; i < n; i++)
        trackPtrs[i] = &*tracks[i];

    return (*this)(&trackPtrs[0], n);
}

bool
V0Filter::operator () (const std::vector<reco::CandidatePtr> & tracks) const
{
    if (tracks.size() != 2)
        return true;

    if (tracks[0]->charge() * tracks[1]->charge() > 0)
        return true;
    
    double invariantMass = (tracks[0]->p4()+tracks[1]->p4()).M();
    if (std::abs(invariantMass - ParticleMasses::k0) < k0sMassWindow)
        return false;

    return true;
}

bool
V0Filter::operator () (const std::vector<const reco::Track *> & tracks) const
{
    return (*this)(&tracks[0], tracks.size());
}


bool
V0Filter::operator () (const reco::Track *tracks, unsigned int n) const
{
    std::vector<const reco::Track*> trackPtrs(n);
    for(unsigned int i = 0; i < n; i++)
        trackPtrs[i] = &tracks[i];

    return (*this)(&trackPtrs[0], n);
}