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::process(Candidate *candidate) const {
// the loop should be processed at least once for limiting the next step
double step = candidate->getCurrentStep();
double z = candidate->getRedshift();
do {
// check if nucleus
int id = candidate->current.getId();
if (not (isNucleus(id)))
return;
int A = massNumber(id);
int Z = chargeNumber(id);
int N = A - Z;
// check if particle can decay
const std::vector<DecayMode> &decays = decayTable[Z * 31 + N];
if (decays.size() == 0)
return;
// find interaction mode with minimum random decay distance
Random &random = Random::instance();
double randDistance = std::numeric_limits<double>::max();
int channel;
double totalRate = 0;
for (size_t i = 0; i < decays.size(); i++) {
double rate = decays[i].rate;
rate /= candidate->current.getLorentzFactor(); // relativistic time dilation
rate /= (1 + z); // rate per light travel distance -> rate per comoving distance
totalRate += rate;
double d = -log(random.rand()) / rate;
if (d > randDistance)
continue;
randDistance = d;
channel = decays[i].channel;
}
// check if interaction doesn't happen
if (step < randDistance) {
// limit next step to a fraction of the mean free path
candidate->limitNextStep(limit / totalRate);
return;
}
// interact and repeat with remaining step
performInteraction(candidate, channel);
step -= randDistance;
} while (step > 0);
}
double NuclearDecay::meanFreePath(int id, double gamma) {
if (not (isNucleus(id)))
return std::numeric_limits<double>::max();
int A = massNumber(id);
int Z = chargeNumber(id);
int N = A - Z;
// check if particle can decay
const std::vector<DecayMode> &decays = decayTable[Z * 31 + N];
if (decays.size() == 0)
return std::numeric_limits<double>::max();
double totalRate = 0;
for (size_t i = 0; i < decays.size(); i++) {
double rate = decays[i].rate;
rate /= gamma;
totalRate += rate;
}
return 1. / totalRate;
}
