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Fix ALP mass suppression #418

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Merged
miquelnebot merged 1 commit into from
Feb 14, 2024
Merged

Fix ALP mass suppression #418

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12 changes: 9 additions & 3 deletions sbncode/EventGenerator/MeVPrtl/Tools/ALP/Meson2ALP_tool.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,7 @@ class Meson2ALP : public IMeVPrtlFlux
double fcG; //!< Axion coupling to gluon
double fcB; //!< Axion coupling to U(1) B boson (before EW symmetry breaking)
double fcW; //!< Axion coupling to SU(2) W bosons (before EW symmetry breaking)
bool fIncludeMassSuppressionFactor; // Whether to include a phenomonological suppression to mixing at high mass

// branching ratios
double fPi0BR;
Expand Down Expand Up @@ -115,6 +116,7 @@ void Meson2ALP::configure(fhicl::ParameterSet const &pset)
fMaxWeightPi0 = pset.get<double>("MaxWeightPi0", 1.);
fMaxWeightEta = pset.get<double>("MaxWeightEta", 1.);
fMaxWeightEtaP = pset.get<double>("MaxWeightEtaP", 1.);
fIncludeMassSuppressionFactor = pset.get<bool>("IncludeMassSuppressionFactor", false);

fPi0BR = Pi0BR();
fEtaBR = EtaBR();
Expand All @@ -136,7 +138,7 @@ double Meson2ALP::EtaBR() const {

double mixing_angle = (1. / sqrt(6)) * (fcG * fpion / ffa) * (fM*fM - (4./9.)*pzero_mass*pzero_mass) / (fM*fM - eta_mass*eta_mass);
double qcd_rate_f = 1.;
if (fM > eta_mass) qcd_rate_f = pow(fM/eta_mass, -1.6);
if (fIncludeMassSuppressionFactor && fM > eta_mass) qcd_rate_f = pow(fM/eta_mass, -1.6);

return mixing_angle*mixing_angle*qcd_rate_f;
}
Expand All @@ -148,7 +150,7 @@ double Meson2ALP::EtaPBR() const {

double mixing_angle = (1. / sqrt(12)) * (fcG * fpion / ffa) * (fM*fM - (16./9.)*pzero_mass*pzero_mass) / (fM*fM - etap_mass*etap_mass);
double qcd_rate_f = 1.;
if (fM > etap_mass) qcd_rate_f = pow(fM/etap_mass, -1.6);
if (fIncludeMassSuppressionFactor && fM > etap_mass) qcd_rate_f = pow(fM/etap_mass, -1.6);

return mixing_angle*mixing_angle*qcd_rate_f;
}
Expand All @@ -160,7 +162,7 @@ double Meson2ALP::Pi0BR() const {
double mixing_angle = (1./6) * (fcG * fpion / ffa) * fM*fM / (fM*fM - pzero_mass*pzero_mass);

double qcd_rate_f = 1.;
if (fM > pzero_mass) qcd_rate_f = pow(fM/pzero_mass, -1.6);
if (fIncludeMassSuppressionFactor && fM > pzero_mass) qcd_rate_f = pow(fM/pzero_mass, -1.6);

return mixing_angle*mixing_angle*qcd_rate_f;
}
Expand All @@ -177,6 +179,10 @@ bool Meson2ALP::MakeFlux(const simb::MCFlux &flux, evgen::ldm::MeVPrtlFlux &alp,

// Energy is same as for meson (don't worry about momentum conservation)
double alp_energy = meson.mom.E();

// ignore if alp isn't energetic enough
if (alp_energy < fM) return false;

double alp_momentum = sqrt(alp_energy*alp_energy - fM*fM);

// Momentum 4-vector
Expand Down