6.2 Geometry parameters

The the g e o m e t r y parameters describe the geometry of the layer. All values are in centimeters. Possible parameters are: R, ZMIN and ZMAX (barrel), or Z, RMIN and RMAX (forward). In addition, there are also PHI1, PHI2, PHI3, and EMPTY_TYPE, for both barrel and forward detectors. These can be used to describe how the layer is sub-divided in sectors in $\phi$: A cylinder or a plane can be subdivided in $\phi$. A repeated form is called a 'cell'. The first $\phi$-limit gives the angle of the first edge of a measuring element (ie. the lowest p o s i t i v e $\phi$ of any measuring sector starting edge). The second $\phi$-limit gives the end of this sector, and the third gives the end of the non-measuring sector (ie. the low-$\phi$ edge of the second measuring sector). This pattern of measuring and non-measuring sectors is the assumed to repeat over the full 360 degrees. The EMPTY_TYPE tells how to interpret the non-measuring sectors : 0 means that the region is empty, ie. no material, and no measurement, and -1 that it contains material, but does not measure.