Geometry and Geometry Database

Min Jeong Kim

Kyungpook National University

mjkim@fnal.gov

March 31, 1999, Offline Meeting

New Shape for Geometry Description : Trap and Pcon

1. Trap(General trapezoid) :

There are two planes which are perpendicular to z axis and their centers are not necessarily on a line parallel to the z axis.
It has 11 parameters.

   (1) Half length along the z axis
   (2) Polar angle of the line joining the centers of the two planes
   (3) Azimuthal angle of the line joining the centers of the two planes
   (4) Half length along the y axis of the first plane
   (5) Half length along the x axis of the first side in y at the first plane
   (6) Half length along the x axis of the second side in y at the first plane
   (7) Angle with respect to the y axis from the center of the first side in y to the center of
        the second side in y at the first plane
   (8) Half length along the y axis of the second plane
   (9) Half length along the x axis of the first side in y at the second plane
   (10) Half length along the x axis of the second side in y at the second plane
   (11) Angle with respect to the y axis from the center of the first side in y to the center of
         the second side in y at the second plane

2. Pcon(Polycone) :

It has at least 9 parameters.

   (1) Phi : The azimuthal angle at which volume begins
   (2) Delta Phi : Opening angle of the volume, which extends from Phi to (Phi + Delta Phi)
   (3) Number of planes perpendicular to the z axis where the dimension of the section is given
        - This should be at least 2 to generate polycone.
   (4) Z coordinate of the section
   (5) Radius of the inner circle in the cross-section
   (6) Radius of the outer circle in the cross-section

Materials List

In the scheme of GeometryBase, material is made of several elements in different ratios.

Sometimes one material corresponds to only one element.

Before the definition of materials, to define basic elements which consist of materials is required.

Materials list was made on the basis of simulation information.

But sometimes the information is too ambiguous to apply the previous principle.

Example <Calorimeter> :

        Even though they are sampling type of active and passive elements, they were represented by
        already calculated values according to the intrinsic characteristics and ratios of elements.
        Therefore it's hard to identify materials which consist of real detector.

***** Example information from GEANT Simulation *****

Material Name : CEM_Stuff
Mass of Molecule : 169.28
Atomic Number : 67.3
Density : 3.897
Radiation Length : 0.22134E+01
Absorption Length : 0.44517E+02

For materials list, detailed information related to elements and their ratios is required.

[Table1] List of calorimeter materials :

	Element Name [Fraction]	Symbol	Atomic Number (Z)	Mass of Molecule (A)	Material Name	Density	Radiation Length	Interaction Length
26	Cemstuff [1]		67.3	169.28	CEM_Stuff	3.897	2.2134	44.517
27	Chastuff [1]		25.	53.66	CHA_Stuff	4.88	2.9451	33.292
28	Whastuff [1]		25.	53.66	WhaStuff	4.88	2.5806	29.177
29	(1) [0.06192] (2) [0.05161] (3) Iron [0.1203] (4) [0.59009E-04] (5) Lead [0.76611]	Fe Pb	26. 82.	55.850 207.190	PEM_Mix	3.9759	1.9154	45.347
30	(1) [0.01443] (2) [0.00916] (3) Aluminum [0.02448] (4) [0.20137E-04] (5) Iron [0.95191]	Al Fe	13. 26.	26.980 55.850	PHA_Mix	5.86639	2.4321	25.084
31	Iron [1]				PLUG misc.steel	5.24667	1.1733	14.180

Muon Geometry

Geometry Database

1. Requirement of Geometry Database

To control the parameters related with the spatial geometry easily.

To avoid the recompilation of the code whenever we make a changement in valuesof parameters which are expected to be frequently replaced since detector geometry could be changed by adjustment of the detector such as misalignment.

2. On the basis of geometry information of include files which reside in each package.

Geometry/Geometry/CdfGeometry.hh
cot/CotGeometry.hh
SvxSim/SvxSim/SvxGeometry.hh
Calor/Calor/CcalGeometry.hh
Calor/Calor/PlugGeometry.hh
Muon/Muon/CmuGeometry.hh
Muon/Muon/CmpGeometry.hh
Muon/Muon/CmxGeometry.hh
Calor/Calor/CalParameters.hh
Calor/Calor/Cal_threshold.hh

3. The development of Geometry Database on ROOT

Simple file layout with several directories named after sub-detectors for the Geometry Database.
Each include file changed into a kind of structure and this structure is written into Geometry Database.
ROOT can handle many kinds of data types including histogram : important for keeping physical parameters.
Interactive browser is available.

4. STAR is using ROOT based Geometry Database - There was a report in ROOT workshop -. We need to pay attention to it.

5. At present, the Geometry Database includes every parameters related to SVXII, ISL, COT, calorimeter and Central Muon Geometry.

6. We tried to read this Geometry Database into simulation code for tracking during last summer.

7. Milestones for Geometry Database

Implementing basic geometry parameters on runII detector : Done

Developing tools for updating and browsing : Done

Providing related documents : At proper time but as soon as possible

Maintaining database : continuously

8. Several questions

Histogram was stored in Geometry Database and it will be used somewhere. But out of ROOT, it looks like a kind of array. Then, when we are in application time, how can we handle that histogram as its native format?

What else constants do we need to add into Geometry Database?

Alignment constants : CalibrationDatabase(?)
Parameterization fpr simulation
Offline constants
etc......