JetUtil.h

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#ifndef JET_JETUTIL_H
#define JET_JETUTIL_H 1

#include <cmath>
#include <algorithm>

class PtGreater {
public:
  template <typename T>
  bool operator()(const T& i, const T& j) {
    return (i.pt() > j.pt());
  }
};

class EtGreater {
public:
  template <typename T>
  bool operator()(const T& i, const T& j) {
    return (i.et() > j.et());
  }
};

class JetUtil {
public:
  static double Phi_0_2pi(double x) {
    while (x >= 2 * M_PI)
      x -= 2 * M_PI;
    while (x < 0.)
      x += 2 * M_PI;
    return x;
  }

  static double Phi_mpi_pi(double x) {
    while (x >= M_PI)
      x -= 2 * M_PI;
    while (x < -M_PI)
      x += 2 * M_PI;
    return x;
  }

  static double dPhi(double phi1, double phi2) {
    phi1 = Phi_0_2pi(phi1);
    phi2 = Phi_0_2pi(phi2);
    return Phi_mpi_pi(phi1 - phi2);
  }

  static double radius(double eta1, double phi1, double eta2, double phi2) {
    const double TWOPI = 2.0 * M_PI;

    phi1 = Phi_0_2pi(phi1);
    phi2 = Phi_0_2pi(phi2);

    double dphi = Phi_0_2pi(phi1 - phi2);
    dphi = std::min(dphi, TWOPI - dphi);
    double deta = eta1 - eta2;

    return sqrt(deta * deta + dphi * dphi);
  }

  template <typename T1, typename T2>
  static double radius(const T1& t1, const T2& t2) {
    return radius(t1->eta(), t1->phi(), t2->eta(), t2->phi());
  }
};
#endif