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[4-mom] Small improvements to 4-momenta calculation #141

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[4-mom] Small improvements to 4-momenta calculation #141

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84 changes: 40 additions & 44 deletions src/FourMomenta.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -224,18 +224,20 @@ std::vector<FourVector<double> > calculate_four_momenta(double initial_mass, con
double m2_sum_1 = 0;
double m_sum_1 = initial_mass;
for (size_t i = 0; i < n_fsp; ++i) {
pp[i][i] = pow(FSPs[i]->mass(), 2);
const auto m = FSPs[i]->mass();

pp[i][i] = m * m;
m2_sum_1 += pp[i][i];
m_sum_1 -= FSPs[i]->mass();
m_sum_1 -= m;
}

// add two-particle invariant masses for those provided
double m2_sum_2 = 0;
for (size_t i = 0; i < axes.size(); ++i) {
if (axes[i]->indices()[0] < axes[i]->indices()[1])
pp[axes[i]->indices()[0]][axes[i]->indices()[1]] = squared_masses[i];
else
pp[axes[i]->indices()[1]][axes[i]->indices()[0]] = squared_masses[i];
const auto row = std::min(axes[i]->indices()[0], axes[i]->indices()[1]);
const auto col = std::max(axes[i]->indices()[0], axes[i]->indices()[1]);
pp[row][col] = squared_masses[i];

m2_sum_2 += squared_masses[i];
}

Expand Down Expand Up @@ -272,59 +274,53 @@ std::vector<FourVector<double> > calculate_four_momenta(double initial_mass, con

std::vector<FourVector<double> > P(n_fsp, FourVector<double>());

for (unsigned i = 0; i < n_fsp; ++i) {
for (unsigned i = 0; i < std::min(n_fsp, static_cast<unsigned>(2)); ++i) {
P[i][0] = (pp[0][i] + pp[1][i]) / m_01; // E
P[i][3] = pow_negative_one(i) * P[i][0] * sqrt(1. - pp[i][i] / pow(P[i][0], 2)); // Z

FourVector<double> p;
if (!std::isfinite(P[i][3]))
return std::vector<FourVector<double> >();
}

if (i < 2) {
for (unsigned i = 2; i < n_fsp; ++ i) {
// Energy E_i = (P_0 * P_i + P_1 * P_i) / (E_1 + E_0)
P[i][0] = (pp[0][i] + pp[1][i]) / (P[0][0] + P[1][0]);

P[i][0] = (pp[0][i] + pp[1][i]) / m_01; // E
P[i][3] = pow_negative_one(i) * P[i][0] * sqrt(1. - pp[i][i] / pow(P[i][0], 2)); // Z
// if E^2 < m^2
if (P[i][0] < sqrt(pp[i][i]))
return std::vector<FourVector<double> >();

if (!std::isfinite(P[i][3]))
return std::vector<FourVector<double> >();
// if p0 and p1 are at rest in m01 rest frame, Z_i := 0
// else Z_i = (P_1 * P_i - P_0 * P_i - (E_1 - E_0) * E_i) / 2 / Z_0
P[i][3] = (P[0][3] == 0) ? 0 : (pp[1][i] - pp[0][i] - (P[1][0] - P[0][0]) * P[i][0]) / 2. / P[0][3];

} else {
if (i < 3) {

// Energy E_i = (P_0 * P_i + P_1 * P_i) / (E_1 + E_0)
P[i][0] = (pp[0][i] + pp[1][i]) / (P[0][0] + P[1][0]);
// p2 in y-z plane, enforce P^2 = m^2
P[i][2] = P[i][0] * sqrt(1 - pp[i][i] / pow(P[i][0], 2) - pow(P[i][3] / P[i][0], 2));

// if E^2 < m^2
if (P[i][0] < sqrt(pp[i][i]))
if (!std::isfinite(P[i][2]))
return std::vector<FourVector<double> >();

// if p0 and p1 are at rest in m01 rest frame, Z_i := 0
// else Z_i = (P_1 * P_i - P_0 * P_i - (E_1 - E_0) * E_i) / 2 / Z_0
P[i][3] = (P[0][3] == 0) ? 0 : (pp[1][i] - pp[0][i] - (P[1][0] - P[0][0]) * P[i][0]) / 2. / P[0][3];

if (i < 3) {

// p2 in y-z plane, enforce P^2 = m^2
P[i][2] = P[i][0] * sqrt(1 - pp[i][i] / pow(P[i][0], 2) - pow(P[i][3] / P[i][0], 2));

if (!std::isfinite(P[i][2]))
return std::vector<FourVector<double> >();

// phasespace check for special case: p0 and p1 are at rest in m01 rest frame
if (n_fsp == 3 and P[0][3] == 0 and !check_invariant_masses(axes, squared_masses, P))
return std::vector<FourVector<double> >();
// phasespace check for special case: p0 and p1 are at rest in m01 rest frame
if (n_fsp == 3 and P[0][3] == 0 and !check_invariant_masses(axes, squared_masses, P))
return std::vector<FourVector<double> >();

} else {
} else {

// if Y_2 == 0, Y_i := 0
// else Y_i = (P_2 * P_i - P_2 * P_i) / Y_2
P[i][2] = (P[2][2] == 0) ? 0 : (P[2][0] * P[i][0] - pp[2][i] - P[2][3] * P[i][3]) / P[2][2];
// if Y_2 == 0, Y_i := 0
// else Y_i = (P_2 * P_i - P_2 * P_i) / Y_2
P[i][2] = (P[2][2] == 0) ? 0 : (P[2][0] * P[i][0] - pp[2][i] - P[2][3] * P[i][3]) / P[2][2];

// if (i < 4) {
// if (i < 4) {

// enforce P^2 = m^2
P[i][1] = P[i][0] * sqrt(1 - pp[i][i] / pow(P[i][0], 2) - pow(P[i][2] / P[i][0], 2) - pow(P[i][3] / P[i][0], 2));
// enforce P^2 = m^2
P[i][1] = P[i][0] * sqrt(1 - pp[i][i] / pow(P[i][0], 2) - pow(P[i][2] / P[i][0], 2) - pow(P[i][3] / P[i][0], 2));

if (!std::isfinite(P[i][1]))
return std::vector<FourVector<double> >();
if (!std::isfinite(P[i][1]))
return std::vector<FourVector<double> >();

// }
}
// }
}
}

Expand Down