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[ALICE3] Add ms & eloss to fasttracker (#9292)
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@jesgum
jesgum authored Jan 17, 2025
1 parent d8db65c commit 90b59b5
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Showing 3 changed files with 181 additions and 100 deletions.
105 changes: 85 additions & 20 deletions ALICE3/Core/FastTracker.cxx
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ namespace fastsim
FastTracker::FastTracker()
{
// base constructor
magneticField = 5; // in kiloGauss
magneticField = 20; // in kiloGauss
applyZacceptance = false;
covMatFactor = 0.99f;
verboseLevel = 0;
Expand All @@ -45,6 +45,20 @@ void FastTracker::AddLayer(TString name, float r, float z, float x0, float xrho,
layers.push_back(newLayer);
}

DetLayer FastTracker::GetLayer(int layer, bool ignoreBarrelLayers)
{
int layerIdx = layer;
if (ignoreBarrelLayers) {
for (int il = 0, trackingLayerIdx = 0; trackingLayerIdx <= layer; il++) {
if (layers[il].type == 0)
continue;
trackingLayerIdx++;
layerIdx = il;
}
}
return layers[layerIdx];
}

void FastTracker::Print()
{
// print out layer setup
Expand Down Expand Up @@ -170,31 +184,58 @@ int FastTracker::FastTrack(o2::track::TrackParCov inputTrack, o2::track::TrackPa
std::array<float, 3> posIni; // provision for != PV
inputTrack.getXYZGlo(posIni);
float initialRadius = std::hypot(posIni[0], posIni[1]);
float kTrackingMargin = 0.1;
int xrhosteps = 100;
bool applyAngularCorrection = true;

// +-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+
// Outward pass to find intercepts
int firstLayerReached = -1;
int lastLayerReached = -1;
new (&outputTrack)(o2::track::TrackParCov)(inputTrack);
for (uint32_t il = 0; il < layers.size(); il++) {
// check if layer is doable
if (layers[il].r < initialRadius)
continue; // this layer should not be attempted, but go ahead
if (layers[il].type == 0)
continue; // inert layer, skip

// check if layer is reached
float targetX = 1e+3;
bool ok = true;
inputTrack.getXatLabR(layers[il].r, targetX, magneticField);
if (targetX > 999)
break; // failed to find intercept

if (!inputTrack.propagateTo(targetX, magneticField)) {
break; // failed to propagate
ok = inputTrack.propagateTo(targetX, magneticField);
if (ok && applyMSCorrection && layers[il].x0 > 0) {
ok = inputTrack.correctForMaterial(layers[il].x0, 0, applyAngularCorrection);
}
if (ok && applyElossCorrection && layers[il].xrho > 0) { // correct in small steps
for (int ise = xrhosteps; ise--;) {
ok = inputTrack.correctForMaterial(0, -layers[il].xrho / xrhosteps, applyAngularCorrection);
if (!ok)
break;
}
}

// was there a problem on this layer?
if (!ok && il > 0) { // may fail to reach target layer due to the eloss
float rad2 = inputTrack.getX() * inputTrack.getX() + inputTrack.getY() * inputTrack.getY();
float fMinRadTrack = 132.;
float maxR = layers[il - 1].r + kTrackingMargin * 2;
float minRad = (fMinRadTrack > 0 && fMinRadTrack < maxR) ? fMinRadTrack : maxR;
if (rad2 - minRad * minRad < kTrackingMargin * kTrackingMargin) { // check previously reached layer
return -5; // did not reach min requested layer
} else {
break;
}
}
if (std::abs(inputTrack.getZ()) > layers[il].z && applyZacceptance) {
break; // out of acceptance bounds
}

if (layers[il].type == 0)
continue; // inert layer, skip

// layer is reached
if (firstLayerReached < 0)
firstLayerReached = il;
Expand All @@ -204,7 +245,7 @@ int FastTracker::FastTrack(o2::track::TrackParCov inputTrack, o2::track::TrackPa

// +-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+
// initialize track at outer point
new (&outputTrack)(o2::track::TrackParCov)(inputTrack);
o2::track::TrackParCov inwardTrack(inputTrack);

// Enlarge covariance matrix
std::array<float, 5> trPars = {0.};
Expand Down Expand Up @@ -241,14 +282,12 @@ int FastTracker::FastTrack(o2::track::TrackParCov inputTrack, o2::track::TrackPa
largeCov[kSnp2] = largeCov[kTgl2] = kLargeErr2Dir;
largeCov[kPtI2] = kLargeErr2PtI * trPars[kPtI] * trPars[kPtI];

outputTrack.setCov(largeCov);
outputTrack.checkCovariance();
inwardTrack.setCov(largeCov);
inwardTrack.checkCovariance();

// +-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+-~-<*>-~-+
// Inward pass to calculate covariances
for (int il = lastLayerReached; il >= firstLayerReached; il--) {
if (layers[il].type == 0)
continue; // inert layer, skip

float targetX = 1e+3;
inputTrack.getXatLabR(layers[il].r, targetX, magneticField);
Expand All @@ -258,6 +297,7 @@ int FastTracker::FastTrack(o2::track::TrackParCov inputTrack, o2::track::TrackPa
if (!inputTrack.propagateTo(targetX, magneticField)) {
continue; // failed to propagate
}

if (std::abs(inputTrack.getZ()) > layers[il].z && applyZacceptance) {
continue; // out of acceptance bounds but continue inwards
}
Expand All @@ -268,20 +308,42 @@ int FastTracker::FastTrack(o2::track::TrackParCov inputTrack, o2::track::TrackPa
std::vector<float> thisHit = {spacePoint[0], spacePoint[1], spacePoint[2]};

// towards adding cluster: move to track alpha
double alpha = outputTrack.getAlpha();
double alpha = inwardTrack.getAlpha();
double xyz1[3]{
TMath::Cos(alpha) * spacePoint[0] + TMath::Sin(alpha) * spacePoint[1],
-TMath::Sin(alpha) * spacePoint[0] + TMath::Cos(alpha) * spacePoint[1],
spacePoint[2]};
if (!(outputTrack.propagateTo(xyz1[0], magneticField)))
if (!inwardTrack.propagateTo(xyz1[0], magneticField))
continue;

const o2::track::TrackParametrization<float>::dim2_t hitpoint = {
static_cast<float>(xyz1[1]),
static_cast<float>(xyz1[2])};
const o2::track::TrackParametrization<float>::dim3_t hitpointcov = {layers[il].resRPhi * layers[il].resRPhi, 0.f, layers[il].resZ * layers[il].resZ};
outputTrack.update(hitpoint, hitpointcov);
outputTrack.checkCovariance();
if (layers[il].type != 0) { // only update covm for tracker hits
const o2::track::TrackParametrization<float>::dim2_t hitpoint = {
static_cast<float>(xyz1[1]),
static_cast<float>(xyz1[2])};
const o2::track::TrackParametrization<float>::dim3_t hitpointcov = {layers[il].resRPhi * layers[il].resRPhi, 0.f, layers[il].resZ * layers[il].resZ};

inwardTrack.update(hitpoint, hitpointcov);
inwardTrack.checkCovariance();
}

if (applyMSCorrection && layers[il].x0 > 0) {
if (!inputTrack.correctForMaterial(layers[il].x0, 0, applyAngularCorrection)) {
return -6;
}
if (!inwardTrack.correctForMaterial(layers[il].x0, 0, applyAngularCorrection)) {
return -6;
}
}
if (applyElossCorrection && layers[il].xrho > 0) {
for (int ise = xrhosteps; ise--;) { // correct in small steps
if (!inputTrack.correctForMaterial(0, layers[il].xrho / xrhosteps, applyAngularCorrection)) {
return -7;
}
if (!inwardTrack.correctForMaterial(0, layers[il].xrho / xrhosteps, applyAngularCorrection)) {
return -7;
}
}
}

if (layers[il].type == 1)
nSiliconPoints++; // count silicon hits
Expand All @@ -293,18 +355,21 @@ int FastTracker::FastTrack(o2::track::TrackParCov inputTrack, o2::track::TrackPa

// backpropagate to original radius
float finalX = 1e+3;
outputTrack.getXatLabR(initialRadius, finalX, magneticField);
inwardTrack.getXatLabR(initialRadius, finalX, magneticField);
if (finalX > 999)
return -3; // failed to find intercept

if (!outputTrack.propagateTo(finalX, magneticField)) {
if (!inwardTrack.propagateTo(finalX, magneticField)) {
return -4; // failed to propagate
}

// only attempt to continue if intercepts are at least four
if (nIntercepts < 4)
return nIntercepts;

outputTrack.setCov(inwardTrack.getCov());
outputTrack.checkCovariance();

// Use covariance matrix based smearing
std::array<double, 15> covMat = {0.};
for (int ii = 0; ii < 15; ii++)
Expand Down
11 changes: 7 additions & 4 deletions ALICE3/Core/FastTracker.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ class FastTracker
virtual ~FastTracker() {}

void AddLayer(TString name, float r, float z, float x0, float xrho, float resRPhi = 0.0f, float resZ = 0.0f, float eff = 0.0f, int type = 0);
DetLayer GetLayer(const int layer, bool ignoreBarrelLayers = true);

void AddSiliconALICE3v4();
void AddSiliconALICE3v1();
Expand All @@ -48,10 +49,12 @@ class FastTracker
std::vector<std::vector<float>> hits; // bookkeep last added hits

// operational
float magneticField; // in kiloGauss (5 = 0.5T, etc)
bool applyZacceptance; // check z acceptance or not
float covMatFactor; // covmat off-diagonal factor to use for covmat fix (negative: no factor)
int verboseLevel; // 0: not verbose, >0 more verbose
float magneticField; // in kiloGauss (5 = 0.5T, etc)
bool applyZacceptance; // check z acceptance or not
float covMatFactor; // covmat off-diagonal factor to use for covmat fix (negative: no factor)
int verboseLevel; // 0: not verbose, >0 more verbose
bool applyMSCorrection; // Apply correction for multiple scattering
bool applyElossCorrection; // Apply correction for eloss (requires MS correction)

uint64_t covMatOK; // cov mat has negative eigenvals
uint64_t covMatNotOK; // cov mat has negative eigenvals
Expand Down
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