CERN Program Library Long Writeup W5013 - CERNLIB ...

Geant 3.10 GEANT User’s Guide HITS400
Origin : R.Brun,H. Boerner Submitted: 01.10.81
Revision : Revised: 18.12.93
Documentation :
Intersection of a track with a cylinder or a plane
CALL GICYL
(R,X1,X2,S1,S2,IC,XINT*,SINT*,PZINT*,IFLAG*)
R
X1
X2
S1
S2
IC
XINT
SINT
PZINT
IFLAG
(REAL) radius of cylinder in cm;
(REAL) array of 6, (x, y, z, dx/ds, dy/ds, dz/ds) of1 st point;
(REAL) array of 6, (x, y, z, dx/ds, dy/ds, dz/ds) of2 nd point;
(REAL) track length s at 1 st point;
(REAL) track length s at 2 nd point;
(INTEGER) type of interpolation:
1 straight line defined as (Xi(1),Xi(2),Xi(3)) +s (Xi(4),Xi(5),Xi(6)), where i
is 1 or 2 according to which of the two points is inside the cylinder;
2 straight line going from (X1(1),X1(2),X1(3))to(X2(1),X2(2),X2(3));
3 third degree curve with:
(
⃗P (s) =⃗a s 3 + ⃗ bs 2 + ⃗c s+ d ⃗ dP
Xi = ⃗P (Si),
⃗ )
∣ i =1, 2
ds
(REAL) array of 6 x, y, z, dx/ds, dy/ds, dz/ds at intersection point;
(REAL) S at intersection point;
(REAL) φ, z, dφ/dr, dz/dr in cylindrical coordinates at intersection point;
(INTEGER) return flag:
0 track does not intersect cylinder;
1 track intersects cylinder.
∣ s=Si
Calculates intersection of track with a cylinder of radius R. The track is approximated by a cubic in the track
length. To improve stability, the coordinate system is shifted.
CALL GIPLAN
(YC,X1,X2,S1,S2,IC,XINT*,SINT*,PZINT*,IFLAG*)
The arguments have the same meaning than in the previous routine, apart from:
YC
(REAL) y coordinate of plane;
Calculates intersection of track with a plane parallel to x − z. The track is approximated by a cubic in the
track length. To improve stability, the coordinate system is shifted.
Note: the default accuracy is 10 microns. The value of EPSI (internal variable) must be changed for a better
precision.
170 HITS400 – 1