heppy::AlphaT Struct Reference

#include <AlphaT.h>

Static Public Member Functions
static double	getAlphaT (const std::vector< double > &et, const std::vector< double > &px, const std::vector< double > &py)

Detailed Description

Definition at line 18 of file AlphaT.h.

Member Function Documentation

double AlphaT::getAlphaT ( const std::vector< double > &  et, const std::vector< double > &  px, const std::vector< double > &  py  )

static

Definition at line 9 of file AlphaT.cc.

References mps_fire::i, dqmiolumiharvest::j, metsig::jet, and mathSSE::sqrt().

                                                        {
    // Momentum sums in transverse plane
    const double sum_et = accumulate(et.begin(), et.end(), 0.);
    const double sum_px = accumulate(px.begin(), px.end(), 0.);
    const double sum_py = accumulate(py.begin(), py.end(), 0.);

    // Minimum Delta Et for two pseudo-jets
    double min_delta_sum_et = -1.;
    for (unsigned i = 0; i < unsigned(1 << (et.size() - 1)); i++) {  //@@ iterate through different combinations
      double delta_sum_et = 0.;
      std::vector<bool> jet;
      for (unsigned j = 0; j < et.size(); j++) {  //@@ iterate through jets
        delta_sum_et += et[j] * (1 - 2 * (int(i >> j) & 1));
      }
      if ((fabs(delta_sum_et) < min_delta_sum_et || min_delta_sum_et < 0.)) {
        min_delta_sum_et = fabs(delta_sum_et);
      }
    }
    if (min_delta_sum_et < 0.) {
      return 0.;
    }

    // Alpha_T
    return (0.5 * (sum_et - min_delta_sum_et) / sqrt(sum_et * sum_et - (sum_px * sum_px + sum_py * sum_py)));
  }