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Fdc strip peakamp rtj #422

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db67796
mcsmear: new FDC smearing options FDC:DRIFT_SMEAR_NS, FDC:CATHODE_SIG…
rjones30 Nov 3, 2026
10dd7e4
mcsmear: apply the FDC anode discriminator threshold FDC_THRESH_KEV t…
rjones30 Nov 3, 2026
782fb13
mcsmear: FDC gas-gain, signal attenuation and threshold options [rtj]
rjones30 Nov 8, 2026
a9b8c02
mcsmear: remove the old FDC wire efficiency-vs-doca curve (GetEfficie…
rjones30 Nov 12, 2026
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77 changes: 64 additions & 13 deletions src/programs/Simulation/mcsmear/FDCSmearer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,14 @@

#include <sstream>

bool fdc_config_t::FDC_EFFVSDOCA(1);
double fdc_config_t::FDC_CATHODE_SIGMA_SET(-1.);
double fdc_config_t::FDC_DRIFT_SMEAR_NS(0.);
double fdc_config_t::FDC_GAIN_SCALE(1.);
double fdc_config_t::FDC_GAIN_PKG[4] = {1., 1., 1., 1.};
double fdc_config_t::FDC_DOCA_ATTEN(0.);
double fdc_config_t::FDC_GAIN_SIGMA(0.);
double fdc_config_t::FDC_STRIP_THR_SET(-1.);
double fdc_config_t::FDC_WIRE_THR_KEV_SET(-1.);

//-----------
// fdc_config_t (constructor)
Expand Down Expand Up @@ -40,7 +47,12 @@ fdc_config_t::fdc_config_t(const std::shared_ptr<const JEvent>& event)
// Calculate ped noise level based on position resolution
// FDC_PED_NOISE = -0.004594 + 0.008711*FDC_CATHODE_SIGMA +
// 0.000010*FDC_CATHODE_SIGMA*FDC_CATHODE_SIGMA; //pC
if (FDC_CATHODE_SIGMA_SET >= 0) FDC_CATHODE_SIGMA = FDC_CATHODE_SIGMA_SET;
FDC_PED_NOISE = -0.0938 + 0.0485*FDC_CATHODE_SIGMA;
jout << "FDC_DRIFT_SMEAR_NS = " << FDC_DRIFT_SMEAR_NS << endl;
jout << "FDC_GAIN_SCALE = " << FDC_GAIN_SCALE << " x package " << FDC_GAIN_PKG[0] << "/" << FDC_GAIN_PKG[1] << "/" << FDC_GAIN_PKG[2] << "/" << FDC_GAIN_PKG[3] << ", FDC_DOCA_ATTEN = " << FDC_DOCA_ATTEN << ", FDC_GAIN_SIGMA = " << FDC_GAIN_SIGMA << ", FDC_STRIP_THRESHOLD = " << FDC_STRIP_THR_SET << " pC, FDC_WIRE_THRESHOLD_KEV = " << FDC_WIRE_THR_KEV_SET << " (< 0: CCDB)" << endl;
jout << "FDC_THRESH_KEV = " << FDC_THRESH_KEV << " (anode wire threshold)" << endl;
jout << "FDC_CATHODE_SIGMA = " << FDC_CATHODE_SIGMA << " um, FDC_PED_NOISE = " << FDC_PED_NOISE << endl;


// load efficiency correction factors
Expand Down Expand Up @@ -68,11 +80,6 @@ fdc_config_t::fdc_config_t(const std::shared_ptr<const JEvent>& event)
channel_efficiencies.push_back( new_strip_efficiencies[2*chamber] );
}
}

FDC_EFFVSDOCA_PAR[0] = 0.999;
FDC_EFFVSDOCA_PAR[1] = 3.75e-4;
FDC_EFFVSDOCA_PAR[2] = 0.506;
FDC_EFFVSDOCA_PAR[3] = 3.75e-2;
}


Expand All @@ -83,10 +90,53 @@ void FDCSmearer::SmearEvent(hddm_s::HDDM *record)
{
double t_max = config->TRIGGER_LOOKBACK_TIME + fdc_config->FDC_TIME_WINDOW;
double threshold = fdc_config->FDC_THRESHOLD_FACTOR * fdc_config->FDC_PED_NOISE; // for sparsification
if (fdc_config->FDC_STRIP_THR_SET >= 0) threshold = fdc_config->FDC_STRIP_THR_SET;
double wire_thr_kev = (fdc_config->FDC_WIRE_THR_KEV_SET >= 0) ? fdc_config->FDC_WIRE_THR_KEV_SET : fdc_config->FDC_THRESH_KEV;
double gain_global = fdc_config->FDC_GAIN_SCALE; // gas gain relative to the simulation: scales the avalanche charge seen on wires and strips

hddm_s::FdcChamberList chambers = record->getFdcChambers();
hddm_s::FdcChamberList::iterator iter;
for (iter = chambers.begin(); iter != chambers.end(); ++iter) {
int pkg = (iter->getModule() - 1) / 2; // FDC package 0-3 (3 planes per module, 2 modules per package)
double gain = gain_global * ((pkg >= 0 && pkg < 4) ? fdc_config->FDC_GAIN_PKG[pkg] : 1.);

// drift-time fluctuation common to the wire hit and the strip hits induced by the same track in this chamber
// (the strips see the charge induced by the wire avalanche, so the drift delay is the same for both); one shift per itrack
std::map<int, double> drift_shift_ns;
auto drift_shift = [&](int itrack) {
if (!config->SMEAR_HITS || fdc_config->FDC_DRIFT_SMEAR_NS <= 0) return 0.;
auto it = drift_shift_ns.find(itrack);
if (it == drift_shift_ns.end())
it = drift_shift_ns.emplace(itrack, gDRandom.SampleGaussian(fdc_config->FDC_DRIFT_SMEAR_NS)).first;
return it->second;
};

// signal attenuation vs the track's doca to its wire in this chamber (charge lost at the cell edge), per itrack, from the anode truth hits
std::map<int, double> atten;
auto atten_of_doca = [&](double d) { return std::max(0.05, 1. - fdc_config->FDC_DOCA_ATTEN * d * d); };
if (fdc_config->FDC_DOCA_ATTEN > 0) {
hddm_s::FdcAnodeWireList awires = iter->getFdcAnodeWires();
for (auto aw = awires.begin(); aw != awires.end(); ++aw) {
hddm_s::FdcAnodeTruthHitList ath = aw->getFdcAnodeTruthHits();
for (auto at = ath.begin(); at != ath.end(); ++at) {
double a = atten_of_doca(at->getD());
auto it = atten.find(at->getItrack());
if (it == atten.end() || a > it->second) atten[at->getItrack()] = a; // the wire with the closest approach
}
}
}
auto atten_of_track = [&](int itrack) { auto it = atten.find(itrack); return (it == atten.end()) ? 1. : it->second; };
// avalanche gain fluctuation, one factor per track in this chamber (the strips see the charge induced by the same wire avalanche)
std::map<int, double> fluct;
auto fluct_of_track = [&](int itrack) {
if (fdc_config->FDC_GAIN_SIGMA <= 0) return 1.;
auto it = fluct.find(itrack);
if (it == fluct.end()) {
double s = fdc_config->FDC_GAIN_SIGMA;
it = fluct.emplace(itrack, exp(gDRandom.SampleGaussian(s) - 0.5 * s * s)).first;
}
return it->second;
};

// Add pedestal noise to strip charge data
hddm_s::FdcCathodeStripList strips = iter->getFdcCathodeStrips();
Expand All @@ -103,8 +153,8 @@ void FDCSmearer::SmearEvent(hddm_s::HDDM *record)
&& !gDRandom.DecideToAcceptHit(fdc_config->GetEfficiencyCorrectionFactor(siter)))
continue;

double q = titer->getQ();
double t = titer->getT();
double q = titer->getQ() * gain * atten_of_track(titer->getItrack()) * fluct_of_track(titer->getItrack());
double t = titer->getT() + drift_shift(titer->getItrack());
if(config->SMEAR_HITS) {
q += gDRandom.SampleGaussian(fdc_config->FDC_PED_NOISE);
t += gDRandom.SampleGaussian(fdc_config->FDC_TDRIFT_SIGMA)*1.0e9;
Expand All @@ -129,16 +179,17 @@ void FDCSmearer::SmearEvent(hddm_s::HDDM *record)
hddm_s::FdcAnodeTruthHitList thits = witer->getFdcAnodeTruthHits();
hddm_s::FdcAnodeTruthHitList::iterator titer;
for (titer = thits.begin(); titer != thits.end(); ++titer) {
// anode discriminator threshold, applied to the energy deposited on the wire
// (dE in GeV, summed by hdgeant4 over the track segments it combined into this hit)
double att = (fdc_config->FDC_DOCA_ATTEN > 0) ? atten_of_doca(titer->getD()) : 1.;
if (titer->getDE() * gain * att * fluct_of_track(titer->getItrack()) * 1e6 < wire_thr_kev)
continue;
// correct simulation efficiencies
if (config->APPLY_EFFICIENCY_CORRECTIONS
&& !gDRandom.DecideToAcceptHit(fdc_config->GetEfficiencyCorrectionFactor(witer)))
continue;
double doca = titer->getD();
if (config->APPLY_EFFICIENCY_CORRECTIONS
&& !gDRandom.DecideToAcceptHit(fdc_config->GetEfficiencyVsDOCA(doca)))
continue;

double t = titer->getT();
double t = titer->getT() + drift_shift(titer->getItrack());
if(config->SMEAR_HITS) {
t += gDRandom.SampleGaussian(fdc_config->FDC_TDRIFT_SIGMA)*1.0e9;
}
Expand Down
23 changes: 8 additions & 15 deletions src/programs/Simulation/mcsmear/FDCSmearer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,14 @@ class fdc_config_t
double FDC_TIME_WINDOW;
double FDC_THRESH_KEV; // fdc anode discriminator threshold

static bool FDC_EFFVSDOCA;
double FDC_EFFVSDOCA_PAR[4];
static double FDC_DRIFT_SMEAR_NS; // FDC:DRIFT_SMEAR_NS, Gaussian drift-time smear (ns) common to the wire and strip hits of one track in one chamber (0 = off)
static double FDC_CATHODE_SIGMA_SET; // FDC:CATHODE_SIGMA, override of FDC_CATHODE_SIGMA in microns (< 0 = use CCDB)
static double FDC_GAIN_SCALE; // FDC:GAIN_SCALE, gas-gain factor applied to the strip charge q and the wire dE before the thresholds (1 = off)
static double FDC_GAIN_PKG[4]; // FDC:GAIN_PKG1..4, extra gain factor per FDC package (modules 1-2, 3-4, 5-6, 7-8), times FDC_GAIN_SCALE (1 = off)
static double FDC_STRIP_THR_SET; // FDC:STRIP_THRESHOLD, strip charge threshold in pC (< 0 = FDC_THRESHOLD_FACTOR * FDC_PED_NOISE from CCDB)
static double FDC_GAIN_SIGMA; // FDC:GAIN_SIGMA s, avalanche gain fluctuation: one log-normal factor exp(s G - s^2/2) per chamber and track, shared by its wire hit and the strips it induces (0 = off)
static double FDC_DOCA_ATTEN; // FDC:DOCA_ATTEN a, signal (wire dE and the track's strip q in the chamber) scaled by max(0.05, 1 - a doca^2), doca in cm (0 = off)
static double FDC_WIRE_THR_KEV_SET; // FDC:WIRE_THRESHOLD_KEV, anode threshold on the gain-scaled wire dE in keV (< 0 = FDC_THRESH_KEV from CCDB)

vector< vector<double > > channel_efficiencies;

Expand Down Expand Up @@ -49,19 +55,6 @@ class fdc_config_t

return channel_efficiencies.at(gPlane).at(element-1);
}

double GetEfficiencyVsDOCA(double doca) {
// Introduce a DOCA-dependent efficiency that cuts off the hit efficiency
// for tracks that cross through the cell at a large distance from the wire.
double eff = FDC_EFFVSDOCA_PAR[0] - FDC_EFFVSDOCA_PAR[1] *
(1 / (pow(FDC_EFFVSDOCA_PAR[2] - doca, 2) +
pow(FDC_EFFVSDOCA_PAR[3], 2))
- 2 * FDC_EFFVSDOCA_PAR[2] * doca /
pow(pow(FDC_EFFVSDOCA_PAR[2], 2) +
pow(FDC_EFFVSDOCA_PAR[3], 2), 2)
);
return (!FDC_EFFVSDOCA)? 1 : (eff < 0)? 0 : eff*eff;
}
};


Expand Down
24 changes: 17 additions & 7 deletions src/programs/Simulation/mcsmear/MyProcessor.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -159,13 +159,23 @@ void MyProcessor::Init(void)
bzero(&input_file_mutex_last_owner, sizeof(pthread_t));
bzero(&smearer_mutex_last_owner, sizeof(pthread_t));

// By default, the empirical fdc DOCA-dependent efficiency
// is applied to fdc wire hits in FDCSmearer. This can be
// disabled by this commandline option.
app->SetDefaultParameter("FDC:USE_EFFVSDOCA", fdc_config_t::FDC_EFFVSDOCA,
"Turn on/off fdc doca-dependent wire hit efficiency,"
" \"0\"=no efficiency correction,"
" \"1\"=standard efficiency correction (default)");
app->SetDefaultParameter("FDC:DRIFT_SMEAR_NS", fdc_config_t::FDC_DRIFT_SMEAR_NS,
"Gaussian drift-time smear in ns, common to the wire and strip hits of one track in one chamber; 0 = off");
app->SetDefaultParameter("FDC:CATHODE_SIGMA", fdc_config_t::FDC_CATHODE_SIGMA_SET,
"FDC_CATHODE_SIGMA override in microns, sets the strip pedestal noise; < 0 = CCDB");
app->SetDefaultParameter("FDC:GAIN_SCALE", fdc_config_t::FDC_GAIN_SCALE,
"FDC gas-gain factor on the strip charge and wire dE before the thresholds; 1 = off");
for (int i = 0; i < 4; i++)
app->SetDefaultParameter("FDC:GAIN_PKG" + std::to_string(i + 1), fdc_config_t::FDC_GAIN_PKG[i],
"FDC extra gain factor for package " + std::to_string(i + 1) + " (times FDC:GAIN_SCALE); 1 = off");
app->SetDefaultParameter("FDC:GAIN_SIGMA", fdc_config_t::FDC_GAIN_SIGMA,
"FDC avalanche gain fluctuation (log-normal sigma), one factor per chamber and track for wire and strips; 0 = off");
app->SetDefaultParameter("FDC:DOCA_ATTEN", fdc_config_t::FDC_DOCA_ATTEN,
"FDC signal attenuation a: wire dE and strip q scaled by max(0.05, 1 - a doca^2) (doca in cm); 0 = off");
app->SetDefaultParameter("FDC:STRIP_THRESHOLD", fdc_config_t::FDC_STRIP_THR_SET,
"FDC strip charge threshold in pC; < 0 = FDC_THRESHOLD_FACTOR * FDC_PED_NOISE (CCDB)");
app->SetDefaultParameter("FDC:WIRE_THRESHOLD_KEV", fdc_config_t::FDC_WIRE_THR_KEV_SET,
"FDC anode threshold on the gain-scaled wire dE in keV; < 0 = FDC_THRESH_KEV (CCDB)");

return; //NOERROR;
}
Expand Down
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