void NuclearDecay::nucleonEmission(Candidate *candidate, int dA, int dZ) const {
Random &random = Random::instance();
int id = candidate->current.getId();
int A = massNumber(id);
int Z = chargeNumber(id);
double EpA = candidate->current.getEnergy() / double(A);
try
{
candidate->current.setId(nucleusId(A - dA, 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.setEnergy(EpA * (A - dA));
Vector3d pos = random.randomInterpolatedPosition(candidate->previous.getPosition(),candidate->current.getPosition());
try
{
candidate->addSecondary(nucleusId(dA, dZ), EpA * dA, pos);
}
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;
}
}
void NuclearDecay::gammaEmission(Candidate *candidate, int channel) const {
int id = candidate->current.getId();
int Z = chargeNumber(id);
int N = massNumber(id) - Z;
// get photon energies and emission probabilities for decay channel
const std::vector<DecayMode> &decays = decayTable[Z * 31 + N];
size_t idecay = decays.size();
while (idecay-- != 0) {
if (decays[idecay].channel == channel)
break;
}
const std::vector<double> &energy = decays[idecay].energy;
const std::vector<double> &intensity = decays[idecay].intensity;
// check if photon emission available
if (energy.size() == 0)
return;
Random &random = Random::instance();
Vector3d pos = random.randomInterpolatedPosition(candidate->previous.getPosition(), candidate->current.getPosition());
for (int i = 0; i < energy.size(); ++i) {
// check if photon of specific energy is emitted
if (random.rand() > intensity[i])
continue;
// create secondary photon; boost to lab frame
double cosTheta = 2 * random.rand() - 1;
double E = energy[i] * candidate->current.getLorentzFactor() * (1. - cosTheta);
candidate->addSecondary(22, E, pos);
}
}
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;
}
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);
}
void MinimumRigidity::process(Candidate *c) const {
double rigidity = fabs(c->current.getEnergy() / chargeNumber(c->current.getId()));
if (rigidity < minRigidity)
reject(c);
}
