Kinematics.h

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//***************************************************************************************
//***************************************************************************************
 
#pragma once
 
#include "NAGASH/Global.h"
#include "NAGASH/Tool.h"
 
namespace NAGASH
{
    class Kinematics : public Tool
    {
    public:
        Kinematics(std::shared_ptr<MSGTool> MSG) : Tool(MSG) {}
        static double MT(const TLorentzVector &l1, const TLorentzVector &l2);
        static double CosthStar(const TLorentzVector &Lepton, const TLorentzVector &AntiLepton);
        static double DeltaR(double, double, double, double);
        static double DeltaPhi(double, double);
 
        static void GetCSFAngles(const TLorentzVector &lep1, const int &charge1, const TLorentzVector &lep2, double ebeam, double &costh, double &phi);
        static void GetVHFAngles(const TLorentzVector &lep1, const int &charge1, const TLorentzVector &lep2, double &costh, double &phi);
        static void GetBDFAngles(const TLorentzVector &tlv1, const int &charge1, const TLorentzVector &tlv2, double &costh, double &phi);
 
        static void GetAiPolynominals(double costh, double phi, std::vector<double> &aipols);
        static std::vector<double> GetAiPolynominals(double costh, double phi);
        static double SumAiPolynominals(std::vector<double> &ai, std::vector<double> &aimom);
 
        // projections
        static void GetProjections(const TLorentzVector &proj, const TLorentzVector &axis, double &par, double &perp);
    };
 
    inline double Kinematics::MT(const TLorentzVector &l1, const TLorentzVector &l2)
    {
        return sqrt(2 * l1.Pt() * l2.Pt() * (1 - cos(l1.DeltaPhi(l2))));
    }
 
    inline double Kinematics::CosthStar(const TLorentzVector &Lepton, const TLorentzVector &AntiLepton)
    {
        double costh, P1_plus, P1_minus, P2_plus, P2_minus, Q, QT;
        TLorentzVector Zboson = Lepton + AntiLepton;
 
        P1_plus = 1 / sqrt(2) * (Lepton.E() + Lepton.Pz());
        P1_minus = 1 / sqrt(2) * (Lepton.E() - Lepton.Pz());
        P2_plus = 1 / sqrt(2) * (AntiLepton.E() + AntiLepton.Pz());
        P2_minus = 1 / sqrt(2) * (AntiLepton.E() - AntiLepton.Pz());
        Q = Zboson.M();
        QT = Zboson.Pt();
        costh = 2 / (Q * sqrt(Q * Q + QT * QT)) * (P1_plus * P2_minus - P2_plus * P1_minus);
        return costh;
    }
 
    inline void Kinematics::GetProjections(const TLorentzVector &proj, const TLorentzVector &axis, double &par, double &perp)
    {
        par = (proj.Px() * axis.Px() + proj.Py() * axis.Py()) / axis.Pt();
        perp = (proj.Py() * axis.Px() - proj.Px() * axis.Py()) / axis.Pt();
    }
 
    inline double Kinematics::SumAiPolynominals(std::vector<double> &ai, std::vector<double> &aimom)
    {
        ai.resize(8);
        aimom.resize(8);
 
        static const double norm = 3. / (16. * TMath::Pi());
        double xsec = 1 + aimom[4] * aimom[4];
        for (int imom = 0; imom < 8; imom++)
            xsec += ((imom == 2) ? 0.5 : 1) * ai[imom] * aimom[imom];
        return xsec * norm;
    }
 
    inline double Kinematics::DeltaR(double eta1, double phi1, double eta2, double phi2)
    {
        return sqrt((eta1 - eta2) * (eta1 - eta2) + pow(DeltaPhi(phi1, phi2), 2));
    }
 
    inline double Kinematics::DeltaPhi(double phi1, double phi2)
    {
        return TVector2::Phi_mpi_pi(phi1 - phi2);
    }
 
} // namespace NAGASH