(present: RK, TS, TI, ML, AA, IG, NK, MF)

TBRootAna
Michel gave us some details of the geometry service he started to work on with Ian.
a) Definition of a LOCAL detector coordinate system
This is the coordinate system used in the geometry files.
The origin (x=y=z=0) is in the ideal Atlas center;
z points parallel to the beam direction of the testbeam;
x points along the radius of the module at the edge where phi(testbeam) = 0;
y complements x,z to produce a right-handed system. phi is defined as usual: phi=0 along x and increases towards y with phi=pi/2 along y.
Given in the geometry files are FOR EACH CELL:
the median: phi, eta, z
and their full extent over those coordinates: dphi, deta, dz

b) Definition of a NOMINAL TESTBEAM coordinate System
This system is fixed on the cryostat (and hence moves with the cryostat).
The choice of coordinates is based on the beam chamber fit output after the beam chamber alignment file has been used and the ytable and xcryo variables have been applied;
z points antiparallel to the testbeam;
y points up (towards the cryostat lid);
x points to the right (if you look into the cryostat though the beam window), forming a right-handed system.
Convention:
z=-86cm : this is the location of the front face of the PS.
x=y=0 : beam hits this spot when I(bend9)=0, ytable=0, xcryo=0

The geometry service will provide a change from one coordinate system to the other. The highest priority goals will be:
- provide access to the geometry files from TBRootAna: given a cell number, the service will get any of the numbers for that cell that are given in the geometry file;
- for a given cell, obtain the geometrical center (x,y,z) in the nominal coordinate system;
- provide some graphical display;
- obtain the volume of the cell.

The change from the local to the nominal coordinate system is done with:
a) a rotation using 3 Euler angles (y-convention)
b) a translation

For the rotation:
phi_rot(HEC) = 19*pi/32
phi_rot(EMEC) = 5*pi/8
theta_rot = pi (for HEC and EMEC)
psi_rot = 0 (for HEC and EMEC)

The translation matrix would contain:
xt = 0
yt = 203.0 cm - 31.2 cm = 171.8 cm
zt = 370.4 cm - 86 cm (convention) = 284.4 cm [this is still being debated between between Sven and Michel]
(NB: contrary to technical drawings, the units for the coordinates here (and in Atlas software) are "cm" !!!)

Michel will provide us with details on slides for the next meeting.

JobOptions
Michel gave us a fast and comprehensive overview over all the lines in the jobOptions file for the standard Ntuple. There was a feeling that it might be good to have two jobOption example files for the Standard Ntuple, one for the HEC and one for the EMEC, so that we won't get errors by forgetting to change important lines by going from one to the other.

AOB
While discussing the geometry service, the idea came up that it would be good to have the errors of the beam chamber fits as entries in the standard Ntuple.