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Fix inconsistencies in the HelixHelper #14654

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Merged
shahor02 merged 1 commit into from
Sep 5, 2025
Merged

Fix inconsistencies in the HelixHelper #14654

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17 changes: 11 additions & 6 deletions Common/DCAFitter/include/DCAFitter/HelixHelper.h
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Original file line number Diff line number Diff line change
Expand Up @@ -63,9 +63,10 @@ struct CrossInfo {
{
const auto& trcA = trax0.rC > trax1.rC ? trax0 : trax1; // designate the largest circle as A
const auto& trcB = trax0.rC > trax1.rC ? trax1 : trax0;
nDCA = 0;
float xDist = trcB.xC - trcA.xC, yDist = trcB.yC - trcA.yC;
float dist2 = xDist * xDist + yDist * yDist, dist = o2::gpu::GPUCommonMath::Sqrt(dist2), rsum = trcA.rC + trcB.rC;
if (o2::gpu::GPUCommonMath::Sqrt(dist) < 1e-12) {
if (dist < 1e-12) {
return nDCA; // circles are concentric?
}
if (dist > rsum) { // circles don't touch, chose a point in between
Expand All @@ -75,9 +76,13 @@ struct CrossInfo {
return nDCA;
}
notTouchingXY(dist, xDist, yDist, trcA, trcB.rC, isCollinear);
} else if (dist + trcB.rC < trcA.rC) { // the small circle is nestled into large one w/o touching
// select the point of closest approach of 2 circles
notTouchingXY(dist, xDist, yDist, trcA, -trcB.rC, isCollinear);
} else if (auto dfr = dist + trcB.rC - trcA.rC; dfr < 0.) { // the small circle is nestled into large one w/o touching
if (dfr > -maxDistXY) {
// select the point of closest approach of 2 circles
notTouchingXY(dist, xDist, yDist, trcA, -trcB.rC, isCollinear);
} else {
return nDCA;
}
} else { // 2 intersection points
if (isCollinear) {
/// collinear tracks, e.g. electrons from photon conversion
Expand All @@ -89,7 +94,7 @@ struct CrossInfo {
xDCA[0] = r2_r * trcA.xC + r1_r * trcB.xC;
yDCA[0] = r2_r * trcA.yC + r1_r * trcB.yC;
nDCA = 1;
} else if (o2::gpu::GPUCommonMath::Sqrt(xDist) < o2::gpu::GPUCommonMath::Sqrt(yDist)) {
} else if (o2::gpu::GPUCommonMath::Abs(xDist) < o2::gpu::GPUCommonMath::Abs(yDist)) {
// to simplify calculations, we move to new frame x->x+Xc0, y->y+Yc0, so that
// the 1st one is centered in origin
float a = (trcA.rC * trcA.rC - trcB.rC * trcB.rC + dist2) / (2. * yDist), b = -xDist / yDist, ab = a * b, bb = b * b;
Expand Down Expand Up @@ -167,7 +172,7 @@ struct CrossInfo {
/// yL(t) = yL + t Ky; Ky = (sinAlp + cosAlp* snp/csp)
/// zL(t) = zL + t Kz; Kz = tgl / csp
/// Note that Kx^2 + Ky^2 + Kz^2 = (1+tgl^2) / csp^2

nDCA = 0;
float dx = trax1.xC - trax0.xC; // for straight line TrackAuxPar stores lab coordinates at referene point!!!
float dy = trax1.yC - trax0.yC; //
float dz = tr1.getZ() - tr0.getZ();
Expand Down