/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_5_3_13_patch3/src/RecoVertex/GhostTrackFitter/src/PositiveSideGhostTrackFitter.cc

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#include <cmath>
#include <vector>

#include "DataFormats/GeometryVector/interface/GlobalVector.h" 
#include "DataFormats/GeometryVector/interface/GlobalPoint.h" 

#include "RecoVertex/GhostTrackFitter/interface/GhostTrackState.h"
#include "RecoVertex/GhostTrackFitter/interface/GhostTrackPrediction.h"

#include "RecoVertex/GhostTrackFitter/interface/PositiveSideGhostTrackFitter.h"

using namespace reco;

GhostTrackPrediction PositiveSideGhostTrackFitter::fit(
                        const GhostTrackFitter::PredictionUpdater &updater,
                        const GhostTrackPrediction &prior,
                        std::vector<GhostTrackState> &states,
                        double &ndof, double &chi2)
{
        double rho = prior.rho();
        for(unsigned int i = 0; i < states.size(); i++) {
                GhostTrackState &state = states[i];
                state.linearize(prior, true, .5 / rho);
        }

        GhostTrackPrediction pred =
                        actualFitter_->fit(updater, prior, states, ndof, chi2);

        double origin = pred.lambda(origin_);
        bool done = true;
        for(unsigned int i = 0; i < states.size(); i++) {
                GhostTrackState &state = states[i];
                double lambda = state.lambda();
                if (lambda < origin && (origin - lambda) < 3.5) {
                        GhostTrackState testState = state;
                        testState.linearize(pred, 2. * origin - lambda);
                        double ndof, chi2;

                        updater.contribution(prior, testState, ndof, chi2, true);
                        if (ndof > 0. && chi2 < 10.) {
                                state = testState;
                                if (state.weight() != 1.)
                                        state.setWeight(3.);
                                done = false;
                        }
                }
        }

        if (!done) {
                for(unsigned int i = 0; i < states.size(); i++) {
                        GhostTrackState &state = states[i];
                        double lambda = state.lambda();
                        if (state.weight() != 1. && lambda < origin) {
                                double weight =
                                        std::exp(10. * (origin - lambda) - .1);
                                state.setWeight(
                                        std::min(state.weight(), weight));
                        }
                }

                pred = actualFitter_->fit(updater, prior, states, ndof, chi2);
        }

        return pred;
}