void ParticleState::setId(int newId) {
id = newId;
if (isNucleus(id)) {
pmass = nuclearMass(id);
charge = chargeNumber(id) * eplus;
if (id < 0)
charge *= -1; // anti-nucleus
} else {
// pmass missing for non-nuclei
charge = HepPID::charge(id) * eplus;
}
}
void ParticleState::setId(int newId) {
id = newId;
if (isNucleus(id)) {
pmass = nuclearMass(id);
charge = chargeNumber(id) * eplus;
if (id < 0)
charge *= -1; // anti-nucleus
} else {
if (abs(id) == 11)
pmass = mass_electron;
charge = HepPID::charge(id) * eplus;
}
}
void NuclearDecay::betaDecay(Candidate *candidate, bool isBetaPlus) const {
double gamma = candidate->current.getLorentzFactor();
int id = candidate->current.getId();
int A = massNumber(id);
int Z = chargeNumber(id);
// beta- decay
int electronId = 11; // electron
int neutrinoId = -12; // anti-electron neutrino
int dZ = 1;
// beta+ decay
if (isBetaPlus) {
electronId = -11; // positron
neutrinoId = 12; // electron neutrino
dZ = -1;
}
// update candidate, nuclear recoil negligible
try
{
candidate->current.setId(nucleusId(A, Z + dZ));
}
catch (std::runtime_error &e)
{
KISS_LOG_ERROR<< "Something went wrong in the NuclearDecay\n" << "Please report this error on https://github.com/CRPropa/CRPropa3/issues including your simulation setup and the following random seed:\n" << Random::instance().getSeed_base64();
throw;
}
candidate->current.setLorentzFactor(gamma);
if (not (haveElectrons or haveNeutrinos))
return;
// Q-value of the decay, subtract total energy of emitted photons
double m1 = nuclearMass(A, Z);
double m2 = nuclearMass(A, Z+dZ);
double Q = (m1 - m2 - mass_electron) * c_squared;
// generate cdf of electron energy, neglecting Coulomb correction
// see Basdevant, Fundamentals in Nuclear Physics, eq. (4.92)
std::vector<double> energies;
std::vector<double> densities; // cdf(E), unnormalized
energies.reserve(51);
densities.reserve(51);
double me = mass_electron * c_squared;
double cdf = 0;
for (int i = 0; i <= 50; i++) {
double E = me + i / 50. * Q;
cdf += E * sqrt(E * E - me * me) * pow(Q + me - E, 2);
energies.push_back(E);
densities.push_back(cdf);
}
// draw random electron energy and angle
Random &random = Random::instance();
double E = interpolate(random.rand() * cdf, densities, energies);
double p = sqrt(E * E - me * me); // p*c
double cosTheta = 2 * random.rand() - 1;
// boost to lab frame
double Ee = gamma * (E - p * cosTheta);
double Enu = gamma * (Q + me - E) * (1 + cosTheta); // pnu*c ~ Enu
Vector3d pos = random.randomInterpolatedPosition(candidate->previous.getPosition(), candidate->current.getPosition());
if (haveElectrons)
candidate->addSecondary(electronId, Ee, pos);
if (haveNeutrinos)
candidate->addSecondary(neutrinoId, Enu, pos);
}
