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Hemispheres.cc
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Hemispheres.cc
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// -*- C++ -*-
#include "Rivet/Projections/Hemispheres.hh"
namespace Rivet {
void Hemispheres::project(const Event& e) {
// Get thrust axes.
const AxesDefinition& ax = applyProjection<AxesDefinition>(e, "Axes");
const Vector3 n = ax.axis1();
getLog() << Log::DEBUG << "Thrust axis = " << n << endl;
FourMomentum p4With, p4Against;
double Evis(0), broadWith(0), broadAgainst(0), broadDenom(0);
const FinalState& fs = applyProjection<FinalState>(e, ax.getProjection("FS"));
const ParticleVector particles = fs.particles();
getLog() << Log::DEBUG << "number of particles = " << particles.size() << endl;
foreach (const Particle& p, particles) {
const FourMomentum p4 = p.momentum();
const Vector3 p3 = p4.vector3();
const double p3Mag = mod(p3);
const double p3Para = dot(p3, n);
const double p3Trans = mod(p3 - p3Para * n);
// Update normalisations
Evis += p4.E();
broadDenom += 2.0 * p3Mag;
// Update the mass and broadening variables
if (p3Para > 0) {
p4With += p4;
broadWith += p3Trans;
} else if (p3Para < 0) {
p4Against += p4;
broadAgainst += p3Trans;
} else {
// In the incredibly unlikely event that a particle goes exactly along the
// thrust plane, add half to each hemisphere.
getLog() << Log::DEBUG << "Particle split between hemispheres" << endl;
p4With += 0.5 * p4;
p4Against += 0.5 * p4;
broadWith += 0.5 * p3Trans;
broadAgainst += 0.5 * p3Trans;
}
}
// Visible energy squared.
_E2vis = Evis * Evis;
// Calculate masses.
const double mass2With = p4With.invariant();
const double mass2Against = p4Against.invariant();
const bool withIsMaxMass = (mass2With > mass2Against);
_M2high = (withIsMaxMass) ? mass2With : mass2Against;
_M2low = (withIsMaxMass) ? mass2Against : mass2With;
// Calculate broadenings.
broadWith /= broadDenom;
broadAgainst /= broadDenom;
const bool withIsMaxBroad = (broadWith > broadAgainst);
_Bmax = (withIsMaxBroad) ? broadWith : broadAgainst;
_Bmin = (withIsMaxBroad) ? broadAgainst : broadWith;
// Calculate high-max correlation flag.
_highMassEqMaxBroad = ((withIsMaxMass && withIsMaxBroad) || (!withIsMaxMass && !withIsMaxBroad));
}
}

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